Ophthalmology – Pediatric Optic Nerve Hypoplasia

Basics

Description

Optic nerve hypoplasia (ONH) is a congenital, nonprogressive optic nerve disorder characterized by an abnormally small optic nerve with a reduced number of retinal ganglion cell axons.

It may be:

• Unilateral
• Bilateral
• Symmetric
• Asymmetric

Visual function ranges from:

• Normal or near-normal
• Mild impairment
• Profound visual loss

ONH may occur as an isolated ocular finding or with:

• Midline brain abnormalities
• Pituitary dysfunction
• Developmental abnormalities

Septo-Optic Dysplasia

Septo-optic dysplasia (SOD) traditionally refers to the presence of at least two of the following:

• Optic nerve hypoplasia
• Pituitary hormone dysfunction
• Midline brain abnormality

Midline abnormalities may include:

• Absent septum pellucidum
• Corpus callosum hypoplasia or agenesis

The term de Morsier syndrome is historical.

Importantly:

Absence of the septum pellucidum alone does not predict endocrine dysfunction, and significant endocrinopathy can occur even with otherwise normal MRI findings.

Epidemiology

ONH is among the most common congenital optic nerve abnormalities in children.

Most cases are:

Sporadic

Bilateral involvement is common, but unilateral disease is frequently encountered.

Risk Factors

Most children have no clearly identifiable prenatal cause.

Reported associations include:

• Maternal alcohol exposure
• Young maternal age
• Prematurity
• Abnormal fetal growth
• Maternal diabetes
• Certain prenatal medication or drug exposures

Older literature has reported associations with:

• Some anticonvulsants
• Quinine
• PCP
• LSD

but these associations are not consistently established.

Maternal Diabetes

Maternal diabetes is particularly associated with:

Superior segmental optic nerve hypoplasia

also called:

Topless disc syndrome

This causes:

• Superior disc hypoplasia
• Superior RNFL loss
• Corresponding inferior visual field defect

Genetics

Most ONH is sporadic.

Rare genetic associations include abnormalities involving:

• HESX1
• SOX2
• SOX3
• OTX2
• PAX6
• Other genes involved in forebrain and pituitary development

Genetic evaluation is especially appropriate when there is:

• Bilateral severe ONH
• Syndromic appearance
• Multiple congenital anomalies
• Strong family history
• Pituitary abnormalities

Associated Genetic and Developmental Disorders

ONH may occur with:

• Aniridia
• Albinism
• Midline developmental syndromes
• Pituitary developmental abnormalities
• Cortical migration disorders

Congenital infection and prenatal cerebral injury may also coexist with optic nerve hypoplasia-like appearances.

Pathophysiology

The primary abnormality is:

Reduced number of optic nerve axons

Possible mechanisms include:

• Abnormal retinal ganglion cell differentiation
• Excessive developmental apoptosis
• Abnormal axonal guidance
• Prenatal injury to the developing visual system

The outer retinal layers are generally preserved unless another retinal disorder is present.

Pathology

Histologically there is:

• Reduced retinal ganglion cell population
• Reduced RNFL
• Reduced optic nerve axons
• Small optic nerve caliber

Clinical Presentation

Bilateral ONH

Usually presents early with:

• Poor visual behavior
• Poor fixation
• Nystagmus
• Developmental concerns

Nystagmus often appears during the first few months of life.

Unilateral ONH

May present later with:

• Strabismus
• Amblyopia
• Failed vision screening
• Incidental optic disc abnormality

A child with unilateral ONH may otherwise be systemically normal.

Visual Acuity

Visual function is highly variable.

It may range from:

20/20 to profound visual impairment

A key principle:

Disc appearance correlates poorly with visual function.

A very small optic nerve may retain useful vision, while a mildly hypoplastic nerve may function poorly.

History

Ask about:

• Poor fixation
• Nystagmus
• Strabismus
• Developmental delay
• Seizures
• Abnormal growth
• Hypoglycemia
• Prolonged neonatal jaundice
• Excessive thirst or urination
• Prenatal alcohol or medication exposure
• Maternal diabetes
• Family history of developmental or endocrine disease

Endocrine Warning Signs

Important clues to pituitary dysfunction include:

• Neonatal hypoglycemia
• Prolonged jaundice
• Poor growth
• Failure to thrive
• Micropenis
• Cryptorchidism
• Recurrent seizures
• Polyuria/polydipsia
• Abnormal puberty

These findings warrant urgent endocrine assessment.

Physical Examination

Perform a complete pediatric ophthalmic examination including:

• Age-appropriate visual acuity
• Pupils
• Ocular alignment
• Motility
• Cycloplegic refraction
• Slit-lamp examination
• Dilated fundus examination

Optic Disc Appearance

Classic findings include:

• Small optic disc
• Pale or gray disc
• Reduced neuroretinal tissue
• Double-ring sign

Double-Ring Sign

The double-ring sign consists of:

• Small true optic nerve
• Surrounding larger ring corresponding to the normal-sized scleral canal and adjacent tissue

It is one of the classic signs of ONH.

Disc–Macula Relationship

Because the optic disc is abnormally small, the distance from:

• Disc center
• Fovea

appears disproportionately large compared with disc diameter.

A reduced disc diameter-to-disc–macula distance ratio supports the diagnosis.

Retinal Vessels

Associated features may include:

• Relative vessel crowding
• Tortuosity
• Immature vascular pattern

These findings are supportive but not diagnostic.

Foveal Hypoplasia

Some children with ONH may have associated:

Foveal hypoplasia

particularly when there is an underlying developmental or syndromic disorder.

OCT can help identify this.

Associated Microphthalmia

ONH may occasionally coexist with:

• Microphthalmia
• Other congenital ocular abnormalities

Nystagmus

Nystagmus is common in:

• Bilateral ONH
• Severe visual impairment

It usually reflects impaired early visual input.

Strabismus

Strabismus is common, especially in:

• Unilateral ONH
• Asymmetric bilateral disease

It may contribute additional amblyopic visual loss.

Pupils

A RAPD may be present with:

• Unilateral ONH
• Markedly asymmetric bilateral ONH

Visual Fields

When reliable testing becomes possible, defects may include:

• Generalized constriction
• Sectoral defects
• Altitudinal defects
• Central defects

Superior segmental ONH classically produces:

Inferior visual field loss

OCT

OCT may demonstrate:

• Reduced RNFL
• Reduced ganglion cell layer
• Small optic nerve head

It is useful for:

• Structural documentation
• Demonstrating asymmetry
• Distinguishing ONH from acquired optic atrophy

Interpretation can be limited by pediatric normative databases.

MRI

MRI of the brain and orbits is generally appropriate in children with ONH to assess for:

• Pituitary abnormalities
• Hypothalamic abnormalities
• Midline brain defects
• Corpus callosum abnormalities
• Cortical migration disorders

MRI Pituitary Findings

Potential findings include:

• Pituitary hypoplasia
• Absent or abnormal pituitary stalk
• Ectopic posterior pituitary bright spot

These increase concern for pituitary hormone deficiency.

However:

A normal MRI does not exclude endocrinopathy.

Important Imaging Principle

MRI can demonstrate associated structural abnormalities, but:

Optic nerve size on neuroimaging correlates imperfectly with visual function.

Clinical examination remains essential.

Endocrine Dysfunction

Pituitary abnormalities are among the most important systemic associations.

Potential deficiencies include:

• Growth hormone
• ACTH/cortisol
• TSH
• Gonadotropins
• Antidiuretic hormone

Growth Hormone Deficiency

Growth hormone deficiency may present with:

• Poor linear growth
• Falling height percentiles
• Delayed growth velocity

Growth charts should be reviewed longitudinally.

Central Hypothyroidism

Central hypothyroidism may be present despite:

• Normal or low-normal TSH

Therefore:

Free T4 is essential

and TSH alone is insufficient to screen for central hypothyroidism.

ACTH Deficiency

ACTH deficiency may cause:

• Hypoglycemia
• Hypotension
• Lethargy
• Adrenal crisis

This is potentially:

Life-threatening

and must not be missed.

Diabetes Insipidus

Central diabetes insipidus may produce:

• Polyuria
• Polydipsia
• Hypernatremia

Further testing may include:

• Serum sodium
• Serum osmolality
• Urine osmolality

Endocrine Evaluation

A low threshold for pediatric endocrinology referral is appropriate.

Initial assessment may include:

• Free T4
• TSH
• Morning cortisol
• Glucose
• IGF-1
• IGFBP-3
• Electrolytes

Additional testing depends on:

• Age
• Growth pattern
• Pubertal status
• Clinical symptoms

Long-Term Endocrine Surveillance

A normal endocrine evaluation in infancy does not guarantee normal future pituitary function.

Hormonal abnormalities may emerge later.

Therefore monitor:

• Height
• Weight
• Growth velocity
• Puberty
• Symptoms of adrenal or thyroid dysfunction

Neurologic Associations

Possible abnormalities include:

• Corpus callosum hypoplasia
• Agenesis of the corpus callosum
• Cortical ectopia
• Pachygyria
• Schizencephaly
• Other migration abnormalities
• Seizure disorders

Developmental Delay

Developmental problems are more common with:

• Bilateral disease
• Severe visual impairment
• Cerebral abnormalities
• Pituitary dysfunction

Assessment may include:

• Developmental pediatrics
• Neurology
• Early-intervention services

Differential Diagnosis

Important differentials include:

• Optic atrophy
• High hyperopia with small crowded discs
• Tilted optic disc
• Optic nerve coloboma
• Peripapillary staphyloma
• Peripapillary atrophy
• Morning glory disc anomaly

ONH vs Optic Atrophy

Optic Nerve Hypoplasia

• Congenitally small disc
• Double-ring sign
• Nonprogressive
• Reduced axon number from development

Optic Atrophy

• Acquired axonal loss
• Usually normal-sized disc initially
• Pallor predominates
• History may reveal previous neurologic or ocular injury

Treatment

There is:

No treatment that can regenerate the hypoplastic optic nerve

Management focuses on maximizing existing visual function and treating associated systemic disease.

Refractive Correction

Perform cycloplegic refraction and correct:

• Hyperopia
• Myopia
• Astigmatism
• Anisometropia

Optimal refractive correction is important during visual development.

Amblyopia Treatment

Amblyopia may coexist with structural optic nerve disease.

Treat when appropriate with:

• Optical correction
• Patching
• Atropine penalization in selected cases

Therapy should be individualized according to visual potential.

Strabismus

Management may include:

• Refractive correction
• Amblyopia treatment
• Strabismus surgery

Surgery may improve:

• Alignment
• Cosmesis
• Binocular function when sufficient vision exists

Nystagmus

Nystagmus surgery may be considered selectively for:

• Significant abnormal head posture
• Null point
• Associated strabismus

It does not treat the underlying optic nerve abnormality.

Protective Eyewear

When visual function is markedly asymmetric:

Protective spectacles should be recommended for the better-seeing eye.

Low-Vision Support

Children with significant bilateral visual impairment should be referred early for:

• Low-vision assessment
• Early-intervention programs
• Educational support
• Orientation and mobility training
• Adaptive technology

Endocrine Treatment

Hormone replacement is directed by pediatric endocrinology.

Examples include:

• Hydrocortisone for adrenal insufficiency
• Levothyroxine for central hypothyroidism
• Growth hormone when appropriate
• Desmopressin for diabetes insipidus

Genetic Counseling

Genetic consultation may be useful in:

• Bilateral severe disease
• Syndromic cases
• Multiple congenital anomalies
• Family history
• Suspected HESX1/SOX-related disease

Stem Cell Therapy

There is currently:

No convincing scientific evidence that stem cell treatment restores visual function in ONH.

It is not an established therapy.

Follow-Up

Ongoing ophthalmic follow-up should assess:

• Visual acuity
• Refraction
• Amblyopia
• Strabismus
• Nystagmus
• Functional visual development

Children often require more frequent review during:

• Amblyopia treatment
• Early visual development

Growth and Development Monitoring

Longitudinal monitoring should include:

• Height
• Weight
• Growth velocity
• Puberty
• Developmental milestones
• Neurologic symptoms

Prognosis

Visual prognosis is:

Highly variable

and depends primarily on residual optic nerve function.

Disc appearance and MRI findings correlate only poorly with visual outcome.

Stability

ONH itself is generally:

Nonprogressive

Apparent visual improvement with age may occur because of:

• Visual maturation
• Improved fixation
• Amblyopia treatment
• Better testing cooperation

This does not represent optic nerve regeneration.

Complications

Potential complications include:

• Severe visual impairment
• Amblyopia
• Strabismus
• Nystagmus
• Developmental delay
• Seizures
• Growth hormone deficiency
• Central hypothyroidism
• ACTH deficiency
• Diabetes insipidus
• Pubertal abnormalities

Ophthalmology Pearls

• Pediatric optic nerve hypoplasia is a congenital, nonprogressive reduction in optic nerve axons.
• The classic fundus finding is a small optic disc with a double-ring sign.
• Bilateral ONH often presents with poor visual behavior and nystagmus; unilateral disease often presents with strabismus or failed screening.
• Visual function correlates poorly with optic disc size or MRI appearance.
• The most important systemic association is hypothalamic-pituitary dysfunction.
• Free T4 is essential because central hypothyroidism may occur with a normal or low-normal TSH.
• ACTH/cortisol deficiency can be life-threatening and should not be missed.
• A normal MRI does not exclude pituitary dysfunction.
• Endocrine abnormalities may appear later, so longitudinal growth and hormonal surveillance is important.
• SOD does not require all three classic findings; ONH, pituitary dysfunction, and midline brain abnormalities may occur in different combinations.
• Maternal diabetes is associated with superior segmental ONH (“topless disc”), which typically causes an inferior visual field defect.
• Treatment focuses on refractive correction, amblyopia therapy, strabismus care, endocrine treatment, developmental support, and low-vision rehabilitation.
• There is currently no proven regenerative or stem-cell treatment for ONH.

Septo-Optic Dysplasia Septo-optic dysplasia (SOD) traditionally refers to the presence of at least two of the following:  Optic nerve hypoplasia Pituitary hormone dysfunction Midline brain abnormality  Midline abnormalities may include:  Absent septum pellucidum Corpus callosum hypoplasia or agenesis  The term de Morsier syndrome is historical. Importantly: Absence of the septum pellucidum alone does not predict endocrine dysfunction, and significant endocrinopathy can occur even with otherwise normal MRI findings.

Epidemiology ONH is among the most common congenital optic nerve abnormalities in children. Most cases are: Sporadic Bilateral involvement is common, but unilateral disease is frequently encountered.

Risk Factors Most children have no clearly identifiable prenatal cause. Reported associations include:  Maternal alcohol exposure Young maternal age Prematurity Abnormal fetal growth Maternal diabetes Certain prenatal medication or drug exposures  Older literature has reported associations with:  Some anticonvulsants Quinine PCP LSD  but these associations are not consistently established.

Maternal Diabetes Maternal diabetes is particularly associated with: Superior segmental optic nerve hypoplasia also called: Topless disc syndrome This causes:  Superior disc hypoplasia Superior RNFL loss Corresponding inferior visual field defect

Genetics Most ONH is sporadic. Rare genetic associations include abnormalities involving:  HESX1 SOX2 SOX3 OTX2 PAX6 Other genes involved in forebrain and pituitary development  Genetic evaluation is especially appropriate when there is:  Bilateral severe ONH Syndromic appearance Multiple congenital anomalies Strong family history Pituitary abnormalities

Associated Genetic and Developmental Disorders ONH may occur with:  Aniridia Albinism Midline developmental syndromes Pituitary developmental abnormalities Cortical migration disorders  Congenital infection and prenatal cerebral injury may also coexist with optic nerve hypoplasia-like appearances.

Pathophysiology The primary abnormality is: Reduced number of optic nerve axons Possible mechanisms include:  Abnormal retinal ganglion cell differentiation Excessive developmental apoptosis Abnormal axonal guidance Prenatal injury to the developing visual system  The outer retinal layers are generally preserved unless another retinal disorder is present.

Pathology Histologically there is:  Reduced retinal ganglion cell population Reduced RNFL Reduced optic nerve axons Small optic nerve caliber

Clinical Presentation Bilateral ONH Usually presents early with:  Poor visual behavior Poor fixation Nystagmus Developmental concerns  Nystagmus often appears during the first few months of life.

Unilateral ONH May present later with:  Strabismus Amblyopia Failed vision screening Incidental optic disc abnormality  A child with unilateral ONH may otherwise be systemically normal.

Visual Acuity Visual function is highly variable. It may range from: 20/20 to profound visual impairment A key principle: Disc appearance correlates poorly with visual function. A very small optic nerve may retain useful vision, while a mildly hypoplastic nerve may function poorly.

History Ask about:  Poor fixation Nystagmus Strabismus Developmental delay Seizures Abnormal growth Hypoglycemia Prolonged neonatal jaundice Excessive thirst or urination Prenatal alcohol or medication exposure Maternal diabetes Family history of developmental or endocrine disease

Endocrine Warning Signs Important clues to pituitary dysfunction include:  Neonatal hypoglycemia Prolonged jaundice Poor growth Failure to thrive Micropenis Cryptorchidism Recurrent seizures Polyuria/polydipsia Abnormal puberty  These findings warrant urgent endocrine assessment.

Physical Examination Perform a complete pediatric ophthalmic examination including:  Age-appropriate visual acuity Pupils Ocular alignment Motility Cycloplegic refraction Slit-lamp examination Dilated fundus examination

Optic Disc Appearance Classic findings include:  Small optic disc Pale or gray disc Reduced neuroretinal tissue Double-ring sign

Double-Ring Sign The double-ring sign consists of:  Small true optic nerve Surrounding larger ring corresponding to the normal-sized scleral canal and adjacent tissue  It is one of the classic signs of ONH.

Disc–Macula Relationship Because the optic disc is abnormally small, the distance from:  Disc center Fovea  appears disproportionately large compared with disc diameter. A reduced disc diameter-to-disc–macula distance ratio supports the diagnosis.

Retinal Vessels Associated features may include:  Relative vessel crowding Tortuosity Immature vascular pattern  These findings are supportive but not diagnostic.

Foveal Hypoplasia Some children with ONH may have associated: Foveal hypoplasia particularly when there is an underlying developmental or syndromic disorder. OCT can help identify this.

Associated Microphthalmia ONH may occasionally coexist with:  Microphthalmia Other congenital ocular abnormalities

Nystagmus Nystagmus is common in:  Bilateral ONH Severe visual impairment  It usually reflects impaired early visual input.

Strabismus Strabismus is common, especially in:  Unilateral ONH Asymmetric bilateral disease  It may contribute additional amblyopic visual loss.

Pupils A RAPD may be present with:  Unilateral ONH Markedly asymmetric bilateral ONH

Visual Fields When reliable testing becomes possible, defects may include:  Generalized constriction Sectoral defects Altitudinal defects Central defects  Superior segmental ONH classically produces: Inferior visual field loss

OCT OCT may demonstrate:  Reduced RNFL Reduced ganglion cell layer Small optic nerve head  It is useful for:  Structural documentation Demonstrating asymmetry Distinguishing ONH from acquired optic atrophy  Interpretation can be limited by pediatric normative databases.

MRI MRI of the brain and orbits is generally appropriate in children with ONH to assess for:  Pituitary abnormalities Hypothalamic abnormalities Midline brain defects Corpus callosum abnormalities Cortical migration disorders

MRI Pituitary Findings Potential findings include:  Pituitary hypoplasia Absent or abnormal pituitary stalk Ectopic posterior pituitary bright spot  These increase concern for pituitary hormone deficiency. However: A normal MRI does not exclude endocrinopathy.

Important Imaging Principle MRI can demonstrate associated structural abnormalities, but: Optic nerve size on neuroimaging correlates imperfectly with visual function. Clinical examination remains essential.

Endocrine Dysfunction Pituitary abnormalities are among the most important systemic associations. Potential deficiencies include:  Growth hormone ACTH/cortisol TSH Gonadotropins Antidiuretic hormone

Growth Hormone Deficiency Growth hormone deficiency may present with:  Poor linear growth Falling height percentiles Delayed growth velocity  Growth charts should be reviewed longitudinally.

Central Hypothyroidism Central hypothyroidism may be present despite:  Normal or low-normal TSH  Therefore: Free T4 is essential and TSH alone is insufficient to screen for central hypothyroidism.

ACTH Deficiency ACTH deficiency may cause:  Hypoglycemia Hypotension Lethargy Adrenal crisis  This is potentially: Life-threatening and must not be missed.

Diabetes Insipidus Central diabetes insipidus may produce:  Polyuria Polydipsia Hypernatremia  Further testing may include:  Serum sodium Serum osmolality Urine osmolality

Endocrine Evaluation A low threshold for pediatric endocrinology referral is appropriate. Initial assessment may include:  Free T4 TSH Morning cortisol Glucose IGF-1 IGFBP-3 Electrolytes  Additional testing depends on:  Age Growth pattern Pubertal status Clinical symptoms

Long-Term Endocrine Surveillance A normal endocrine evaluation in infancy does not guarantee normal future pituitary function. Hormonal abnormalities may emerge later. Therefore monitor:  Height Weight Growth velocity Puberty Symptoms of adrenal or thyroid dysfunction

Neurologic Associations Possible abnormalities include:  Corpus callosum hypoplasia Agenesis of the corpus callosum Cortical ectopia Pachygyria Schizencephaly Other migration abnormalities Seizure disorders

Developmental Delay Developmental problems are more common with:  Bilateral disease Severe visual impairment Cerebral abnormalities Pituitary dysfunction  Assessment may include:  Developmental pediatrics Neurology Early-intervention services

Differential Diagnosis Important differentials include:  Optic atrophy High hyperopia with small crowded discs Tilted optic disc Optic nerve coloboma Peripapillary staphyloma Peripapillary atrophy Morning glory disc anomaly

ONH vs Optic Atrophy Optic Nerve Hypoplasia  Congenitally small disc Double-ring sign Nonprogressive Reduced axon number from development  Optic Atrophy  Acquired axonal loss Usually normal-sized disc initially Pallor predominates History may reveal previous neurologic or ocular injury

Treatment There is: No treatment that can regenerate the hypoplastic optic nerve Management focuses on maximizing existing visual function and treating associated systemic disease.

Refractive Correction Perform cycloplegic refraction and correct:  Hyperopia Myopia Astigmatism Anisometropia  Optimal refractive correction is important during visual development.

Amblyopia Treatment Amblyopia may coexist with structural optic nerve disease. Treat when appropriate with:  Optical correction Patching Atropine penalization in selected cases  Therapy should be individualized according to visual potential.

Strabismus Management may include:  Refractive correction Amblyopia treatment Strabismus surgery  Surgery may improve:  Alignment Cosmesis Binocular function when sufficient vision exists

Nystagmus Nystagmus surgery may be considered selectively for:  Significant abnormal head posture Null point Associated strabismus  It does not treat the underlying optic nerve abnormality.

Protective Eyewear When visual function is markedly asymmetric: Protective spectacles should be recommended for the better-seeing eye.

Low-Vision Support Children with significant bilateral visual impairment should be referred early for:  Low-vision assessment Early-intervention programs Educational support Orientation and mobility training Adaptive technology

Endocrine Treatment Hormone replacement is directed by pediatric endocrinology. Examples include:  Hydrocortisone for adrenal insufficiency Levothyroxine for central hypothyroidism Growth hormone when appropriate Desmopressin for diabetes insipidus

Genetic Counseling Genetic consultation may be useful in:  Bilateral severe disease Syndromic cases Multiple congenital anomalies Family history Suspected HESX1/SOX-related disease

Stem Cell Therapy There is currently: No convincing scientific evidence that stem cell treatment restores visual function in ONH. It is not an established therapy.

Follow-Up Ongoing ophthalmic follow-up should assess:  Visual acuity Refraction Amblyopia Strabismus Nystagmus Functional visual development  Children often require more frequent review during:  Amblyopia treatment Early visual development

Growth and Development Monitoring Longitudinal monitoring should include:  Height Weight Growth velocity Puberty Developmental milestones Neurologic symptoms

Prognosis Visual prognosis is: Highly variable and depends primarily on residual optic nerve function. Disc appearance and MRI findings correlate only poorly with visual outcome.

Stability ONH itself is generally: Nonprogressive Apparent visual improvement with age may occur because of:  Visual maturation Improved fixation Amblyopia treatment Better testing cooperation  This does not represent optic nerve regeneration.

Complications Potential complications include:  Severe visual impairment Amblyopia Strabismus Nystagmus Developmental delay Seizures Growth hormone deficiency Central hypothyroidism ACTH deficiency Diabetes insipidus Pubertal abnormalities

Ophthalmology Pearls  Pediatric optic nerve hypoplasia is a congenital, nonprogressive reduction in optic nerve axons. The classic fundus finding is a small optic disc with a double-ring sign. Bilateral ONH often presents with poor visual behavior and nystagmus; unilateral disease often presents with strabismus or failed screening. Visual function correlates poorly with optic disc size or MRI appearance. The most important systemic association is hypothalamic-pituitary dysfunction. Free T4 is essential because central hypothyroidism may occur with a normal or low-normal TSH. ACTH/cortisol deficiency can be life-threatening and should not be missed. A normal MRI does not exclude pituitary dysfunction. Endocrine abnormalities may appear later, so longitudinal growth and hormonal surveillance is important. SOD does not require all three classic findings; ONH, pituitary dysfunction, and midline brain abnormalities may occur in different combinations. Maternal diabetes is associated with superior segmental ONH (“topless disc”), which typically causes an inferior visual field defect. Treatment focuses on refractive correction, amblyopia therapy, strabismus care, endocrine treatment, developmental support, and low-vision rehabilitation. There is currently no proven regenerative or stem-cell treatment for ONH.

Ophthalmology – Pattern Dystrophy

Basics

Description

Pattern dystrophies of the retinal pigment epithelium (RPE) are a heterogeneous group of inherited macular disorders characterized by abnormal deposition of lipofuscin and pigment at the level of the:

• RPE
• Photoreceptor–RPE interface

They are usually:

• Bilateral
• Slowly progressive
• Relatively symmetric

but the appearance can differ between the two eyes.

Many patients are discovered incidentally and retain useful central vision for decades.

Major Clinical Patterns

Classically described phenotypes include:

• Butterfly-shaped pattern dystrophy
• Reticular pattern dystrophy
• Adult-onset foveomacular vitelliform lesion/dystrophy
• Fundus pulverulentus
• Multifocal pattern dystrophy simulating fundus flavimaculatus

These categories overlap considerably.

A single patient may:

• Change phenotype over time
• Show different patterns between eyes
• Develop increasing RPE atrophy with age

Epidemiology

The true incidence and prevalence are uncertain because of:

• Mild symptoms
• Variable phenotype
• Overlap with age-related macular disease
• Variable penetrance

Men and women are affected approximately equally.

Presentation is often in:

• Young or middle adulthood

although clinically significant symptoms may not appear until later life.

Genetics

Most classic pattern dystrophies are inherited in an:

Autosomal dominant

fashion.

The most important gene is:

PRPH2

formerly called:

RDS/peripherin

PRPH2 is located on chromosome 6 and encodes a photoreceptor outer-segment membrane protein important for:

• Disc structure
• Photoreceptor maintenance

PRPH2 Phenotypic Variability

PRPH2 variants can produce a wide spectrum of retinal disease, including:

• Pattern dystrophy
• Adult-onset vitelliform lesions
• Central areolar choroidal dystrophy
• Cone–rod dystrophy
• Retinitis pigmentosa-like phenotypes

Therefore:

The same gene can produce markedly different retinal appearances even within the same family.

Other Genetic Associations

Not all pattern dystrophy phenotypes are caused by PRPH2.

Other implicated genes include:

• BEST1
• IMPG1
• IMPG2

depending on phenotype.

Genetic testing is most useful when:

• Diagnosis is uncertain
• Family counseling is needed
• Presentation is atypical
• There is overlap with another inherited retinal disease

Mitochondrial Association

A distinctive macular pattern dystrophy is strongly associated with:

Maternally inherited diabetes and deafness (MIDD)

usually caused by the mitochondrial DNA variant:

m.3243A>G in MT-TL1

The macular phenotype may show:

• Circumferential RPE atrophy
• Pigmentary changes surrounding the fovea
• Relative foveal sparing early

MIDD Clinical Clues

Consider MIDD when pattern dystrophy occurs with:

• Diabetes mellitus
• Sensorineural hearing loss
• Maternal inheritance pattern
• Short stature
• Other mitochondrial features

Because mitochondrial DNA is maternally inherited:

Affected fathers do not transmit the disorder, whereas affected mothers may transmit it to offspring.

Pathophysiology

Pattern dystrophies involve abnormal function of:

• Photoreceptor outer segments
• RPE

with accumulation of:

Lipofuscin and other pigmentary material

Over time this may lead to:

• RPE degeneration
• Photoreceptor loss
• Outer retinal atrophy

Complications of Progressive Disease

With age, patients may develop:

• Geographic-like RPE atrophy
• Photoreceptor loss
• Central visual decline
• Macular neovascularization (MNV/CNV)

Clinical Presentation

Many patients are initially:

Asymptomatic

When symptoms occur they may include:

• Mild reduction in central vision
• Metamorphopsia
• Difficulty reading
• Central scotoma
• Reduced contrast sensitivity

Symptoms usually progress slowly.

Fundus Appearance

Typical fundus findings include:

• Yellow
• Gray
• Orange
• Brown

pigmentary deposits at the macula.

The distribution varies according to phenotype.

Butterfly Pattern Dystrophy

Characteristic finding:

Butterfly- or spoke-shaped pigmentary material centered on the fovea

The lesion consists of:

• Yellow-gray material
• Pigment clumping
• RPE alteration

Reticular Pattern Dystrophy

Shows:

• Reticular
• Net-like
• Branching pigment pattern

typically around the posterior pole.

Adult-Onset Foveomacular Vitelliform Phenotype

Usually demonstrates a:

Round or oval yellow subfoveal vitelliform lesion

It may resemble:

• Best disease
• Acquired vitelliform lesion
• Early AMD

Patients often present in:

• Middle or later adulthood

Fundus Pulverulentus

Characterized by:

• Numerous fine
• Dust-like
• Gray-white or pigmentary macular spots

The changes are usually subtle.

Multifocal Pattern Dystrophy

May produce multiple:

• Yellow-white flecks
• Pigmentary lesions

and can resemble:

Stargardt disease / fundus flavimaculatus

Visual Acuity

Visual acuity is often:

• Normal
• Mildly reduced

for many years.

Substantial loss usually occurs because of:

• Central RPE atrophy
• Photoreceptor loss
• MNV/CNV

Color Vision

Color vision is usually:

Normal early

Abnormality may occur with advanced macular or cone dysfunction.

Visual Fields

Visual fields are often normal early.

Advanced disease may produce:

• Central scotoma
• Paracentral scotoma

Dark Adaptation

Dark adaptation is usually:

Normal or minimally affected

which helps distinguish many pattern dystrophies from more diffuse retinal dystrophies.

OCT

Optical coherence tomography is one of the most useful investigations.

Findings may include:

• Hyperreflective material between RPE and photoreceptors
• Subretinal vitelliform material
• RPE irregularity
• Ellipsoid-zone disruption
• Outer retinal thinning
• RPE atrophy

OCT in Vitelliform Lesions

The yellow lesion usually corresponds to:

Hyperreflective subretinal material above the RPE

Later stages may show:

• Collapse of material
• Outer retinal disruption
• RPE atrophy

Fundus Autofluorescence

FAF is particularly useful because lipofuscin is autofluorescent.

Early lesions often demonstrate:

Increased autofluorescence

because of accumulated lipofuscin.

Areas of advanced RPE loss demonstrate:

Reduced or absent autofluorescence

Fluorescein Angiography

FA findings vary with the pattern.

Pigmented areas may cause:

• Blocked fluorescence

Areas of RPE atrophy may produce:

• Window defects
• Hyperfluorescence without leakage

FA is particularly useful when:

MNV/CNV is suspected

OCT Angiography

OCTA may detect:

• Neovascular networks
• Subclinical MNV

without dye injection.

It is particularly helpful when:

• Fluid or hemorrhage is suspicious for neovascularization
• Structural OCT findings are equivocal

Electroretinography

Full-field ERG is usually:

Normal

because the disease is predominantly macular.

An abnormal full-field ERG should raise suspicion for:

• Cone dystrophy
• Cone–rod dystrophy
• More generalized inherited retinal disease

Electrooculography

EOG may be:

• Normal
• Mildly reduced

It is not routinely needed for diagnosis.

Diagnosis

Diagnosis is based on:

• Characteristic fundus appearance
• OCT
• Fundus autofluorescence
• Family history

Additional testing is directed by phenotype.

When Genetic Testing Is Helpful

Consider testing when:

• PRPH2-associated disease is suspected
• There is a strong family history
• MIDD is suspected
• Diagnosis overlaps with Best disease or Stargardt disease
• Counseling is needed

Differential Diagnosis

Important differentials include:

• Age-related macular degeneration
• Stargardt disease
• Best vitelliform macular dystrophy
• Acquired vitelliform lesion
• Dominant drusen
• Central areolar choroidal dystrophy
• Cone dystrophy
• Benign concentric annular macular dystrophy
• Drug toxicity
• Chronic central serous chorioretinopathy

Pattern Dystrophy vs AMD

This distinction becomes particularly important in older patients.

Pattern dystrophy tends to show:

• Characteristic geometric or patterned pigment
• Family history
• Relatively preserved vision for age
• Bilateral similar lesions
• Hyperautofluorescent lipofuscin

AMD more typically shows:

• Drusen
• Pigmentary changes without a characteristic pattern
• Geographic atrophy
• Age-related macular neovascularization

The two may coexist.

Pattern Dystrophy vs Stargardt Disease

Stargardt disease typically has:

• Younger onset
• More progressive central visual loss
• Flecks extending beyond the macula
• Characteristic FAF changes
• ABCA4-associated inheritance

Pattern dystrophy is more often:

• Autosomal dominant
• Later onset
• Milder

Adult-Onset Vitelliform Lesion vs Best Disease

Best disease usually:

• Begins earlier
• Has BEST1-associated inheritance
• Shows abnormal EOG in classic disease

Adult-onset vitelliform lesions:

• Present later
• Are generally smaller
• Have more limited visual effect early
• May be associated with PRPH2, BEST1, IMPG1, or IMPG2

Treatment

There is currently:

No treatment that reverses the underlying inherited RPE dystrophy

Management focuses on:

• Monitoring
• Treating complications
• Genetic counseling
• Low-vision support when necessary

Macular Neovascularization

The most important treatable complication is:

MNV/CNV

Suspect it when there is:

• Sudden visual decline
• New metamorphopsia
• New hemorrhage
• Intraretinal or subretinal fluid on OCT

Anti-VEGF Therapy

The modern first-line treatment for active MNV/CNV is:

Intravitreal anti-VEGF therapy

Agents include:

• Bevacizumab
• Ranibizumab
• Aflibercept
• Faricimab in selected settings

Treatment generally follows OCT-guided disease activity.

Photodynamic Therapy

PDT was historically used for CNV associated with pattern dystrophy.

Today it has largely been replaced by:

Anti-VEGF therapy

because anti-VEGF generally provides better anatomic and visual outcomes.

Monitoring

Patients without complications may be reviewed:

Approximately annually

depending on:

• Age
• Phenotype
• Visual symptoms
• Degree of atrophy

Home Monitoring

Patients should be advised to report:

• New distortion
• New central blur
• New scotoma

An:

Amsler grid

may be useful for home monitoring.

Low-Vision Rehabilitation

Referral is appropriate when central atrophy causes:

• Reading difficulty
• Reduced contrast sensitivity
• Loss of useful central vision

Genetic Counseling

Counseling should address:

• Autosomal dominant inheritance in many PRPH2 cases
• Variable expression
• Incomplete penetrance in some families
• Mitochondrial inheritance when MIDD is present

Prognosis

Overall visual prognosis is generally:

Good

Most patients retain useful central vision for many years.

Many maintain:

• Reading vision
• Functional independence

into late adulthood.

Poorer Prognostic Factors

More significant visual loss occurs with:

• Extensive RPE atrophy
• Foveal photoreceptor loss
• MNV/CNV
• Recurrent macular hemorrhage

Complications

Important complications include:

• Progressive central visual loss
• RPE atrophy
• Photoreceptor loss
• Central scotoma
• Macular neovascularization
• Subretinal hemorrhage

Ophthalmology Pearls

• Pattern dystrophy is a group of inherited macular RPE disorders characterized by patterned lipofuscin and pigment deposition.
• Most classic cases are autosomal dominant and associated with PRPH2, formerly called RDS/peripherin.
• The phenotype can change with age and may differ between the two eyes or among members of the same family.
• Important patterns include butterfly, reticular, adult-onset vitelliform, fundus pulverulentus, and multifocal pattern dystrophy.
• OCT commonly shows subretinal or RPE-level hyperreflective material with outer retinal disruption.
• FAF is often hyperautofluorescent early from lipofuscin accumulation and becomes hypoautofluorescent where RPE atrophy develops.
• Full-field ERG is usually normal, reflecting the predominantly macular nature of the disease.
• MIDD should be considered when pattern dystrophy accompanies diabetes and sensorineural deafness, particularly with maternal inheritance.
• Pattern dystrophy can mimic AMD, Stargardt disease, and Best disease.
• Most patients retain useful vision for decades.
• The major treatable complication is macular neovascularization, for which intravitreal anti-VEGF is first-line therapy.
• New metamorphopsia, hemorrhage, or sudden visual loss should prompt urgent OCT assessment for MNV/CNV.

Major Clinical Patterns Classically described phenotypes include:  Butterfly-shaped pattern dystrophy Reticular pattern dystrophy Adult-onset foveomacular vitelliform lesion/dystrophy Fundus pulverulentus Multifocal pattern dystrophy simulating fundus flavimaculatus  These categories overlap considerably. A single patient may:  Change phenotype over time Show different patterns between eyes Develop increasing RPE atrophy with age

Epidemiology The true incidence and prevalence are uncertain because of:  Mild symptoms Variable phenotype Overlap with age-related macular disease Variable penetrance  Men and women are affected approximately equally. Presentation is often in:  Young or middle adulthood  although clinically significant symptoms may not appear until later life.

Genetics Most classic pattern dystrophies are inherited in an: Autosomal dominant fashion. The most important gene is: PRPH2 formerly called: RDS/peripherin PRPH2 is located on chromosome 6 and encodes a photoreceptor outer-segment membrane protein important for:  Disc structure Photoreceptor maintenance

PRPH2 Phenotypic Variability PRPH2 variants can produce a wide spectrum of retinal disease, including:  Pattern dystrophy Adult-onset vitelliform lesions Central areolar choroidal dystrophy Cone–rod dystrophy Retinitis pigmentosa-like phenotypes  Therefore: The same gene can produce markedly different retinal appearances even within the same family.

Other Genetic Associations Not all pattern dystrophy phenotypes are caused by PRPH2. Other implicated genes include:  BEST1 IMPG1 IMPG2  depending on phenotype. Genetic testing is most useful when:  Diagnosis is uncertain Family counseling is needed Presentation is atypical There is overlap with another inherited retinal disease

Mitochondrial Association A distinctive macular pattern dystrophy is strongly associated with: Maternally inherited diabetes and deafness (MIDD) usually caused by the mitochondrial DNA variant: m.3243A>G in MT-TL1 The macular phenotype may show:  Circumferential RPE atrophy Pigmentary changes surrounding the fovea Relative foveal sparing early

MIDD Clinical Clues Consider MIDD when pattern dystrophy occurs with:  Diabetes mellitus Sensorineural hearing loss Maternal inheritance pattern Short stature Other mitochondrial features  Because mitochondrial DNA is maternally inherited: Affected fathers do not transmit the disorder, whereas affected mothers may transmit it to offspring.

Pathophysiology Pattern dystrophies involve abnormal function of:  Photoreceptor outer segments RPE  with accumulation of: Lipofuscin and other pigmentary material Over time this may lead to:  RPE degeneration Photoreceptor loss Outer retinal atrophy

Complications of Progressive Disease With age, patients may develop:  Geographic-like RPE atrophy Photoreceptor loss Central visual decline Macular neovascularization (MNV/CNV)

Clinical Presentation Many patients are initially: Asymptomatic When symptoms occur they may include:  Mild reduction in central vision Metamorphopsia Difficulty reading Central scotoma Reduced contrast sensitivity  Symptoms usually progress slowly.

Fundus Appearance Typical fundus findings include:  Yellow Gray Orange Brown  pigmentary deposits at the macula. The distribution varies according to phenotype.

Butterfly Pattern Dystrophy Characteristic finding: Butterfly- or spoke-shaped pigmentary material centered on the fovea The lesion consists of:  Yellow-gray material Pigment clumping RPE alteration

Reticular Pattern Dystrophy Shows:  Reticular Net-like Branching pigment pattern  typically around the posterior pole.

Adult-Onset Foveomacular Vitelliform Phenotype Usually demonstrates a: Round or oval yellow subfoveal vitelliform lesion It may resemble:  Best disease Acquired vitelliform lesion Early AMD  Patients often present in:  Middle or later adulthood

Fundus Pulverulentus Characterized by:  Numerous fine Dust-like Gray-white or pigmentary macular spots  The changes are usually subtle.

Multifocal Pattern Dystrophy May produce multiple:  Yellow-white flecks Pigmentary lesions  and can resemble: Stargardt disease / fundus flavimaculatus

Visual Acuity Visual acuity is often:  Normal Mildly reduced  for many years. Substantial loss usually occurs because of:  Central RPE atrophy Photoreceptor loss MNV/CNV

Color Vision Color vision is usually: Normal early Abnormality may occur with advanced macular or cone dysfunction.

Visual Fields Visual fields are often normal early. Advanced disease may produce:  Central scotoma Paracentral scotoma

Dark Adaptation Dark adaptation is usually: Normal or minimally affected which helps distinguish many pattern dystrophies from more diffuse retinal dystrophies.

OCT Optical coherence tomography is one of the most useful investigations. Findings may include:  Hyperreflective material between RPE and photoreceptors Subretinal vitelliform material RPE irregularity Ellipsoid-zone disruption Outer retinal thinning RPE atrophy

OCT in Vitelliform Lesions The yellow lesion usually corresponds to: Hyperreflective subretinal material above the RPE Later stages may show:  Collapse of material Outer retinal disruption RPE atrophy

Fundus Autofluorescence FAF is particularly useful because lipofuscin is autofluorescent. Early lesions often demonstrate: Increased autofluorescence because of accumulated lipofuscin. Areas of advanced RPE loss demonstrate: Reduced or absent autofluorescence

Fluorescein Angiography FA findings vary with the pattern. Pigmented areas may cause:  Blocked fluorescence  Areas of RPE atrophy may produce:  Window defects Hyperfluorescence without leakage  FA is particularly useful when: MNV/CNV is suspected

OCT Angiography OCTA may detect:  Neovascular networks Subclinical MNV  without dye injection. It is particularly helpful when:  Fluid or hemorrhage is suspicious for neovascularization Structural OCT findings are equivocal

Electroretinography Full-field ERG is usually: Normal because the disease is predominantly macular. An abnormal full-field ERG should raise suspicion for:  Cone dystrophy Cone–rod dystrophy More generalized inherited retinal disease

Electrooculography EOG may be:  Normal Mildly reduced  It is not routinely needed for diagnosis.

Diagnosis Diagnosis is based on:  Characteristic fundus appearance OCT Fundus autofluorescence Family history  Additional testing is directed by phenotype.

When Genetic Testing Is Helpful Consider testing when:  PRPH2-associated disease is suspected There is a strong family history MIDD is suspected Diagnosis overlaps with Best disease or Stargardt disease Counseling is needed

Differential Diagnosis Important differentials include:  Age-related macular degeneration Stargardt disease Best vitelliform macular dystrophy Acquired vitelliform lesion Dominant drusen Central areolar choroidal dystrophy Cone dystrophy Benign concentric annular macular dystrophy Drug toxicity Chronic central serous chorioretinopathy

Pattern Dystrophy vs AMD This distinction becomes particularly important in older patients. Pattern dystrophy tends to show:  Characteristic geometric or patterned pigment Family history Relatively preserved vision for age Bilateral similar lesions Hyperautofluorescent lipofuscin  AMD more typically shows:  Drusen Pigmentary changes without a characteristic pattern Geographic atrophy Age-related macular neovascularization  The two may coexist.

Pattern Dystrophy vs Stargardt Disease Stargardt disease typically has:  Younger onset More progressive central visual loss Flecks extending beyond the macula Characteristic FAF changes ABCA4-associated inheritance  Pattern dystrophy is more often:  Autosomal dominant Later onset Milder

Adult-Onset Vitelliform Lesion vs Best Disease Best disease usually:  Begins earlier Has BEST1-associated inheritance Shows abnormal EOG in classic disease  Adult-onset vitelliform lesions:  Present later Are generally smaller Have more limited visual effect early May be associated with PRPH2, BEST1, IMPG1, or IMPG2

Treatment There is currently: No treatment that reverses the underlying inherited RPE dystrophy Management focuses on:  Monitoring Treating complications Genetic counseling Low-vision support when necessary

Macular Neovascularization The most important treatable complication is: MNV/CNV Suspect it when there is:  Sudden visual decline New metamorphopsia New hemorrhage Intraretinal or subretinal fluid on OCT

Anti-VEGF Therapy The modern first-line treatment for active MNV/CNV is: Intravitreal anti-VEGF therapy Agents include:  Bevacizumab Ranibizumab Aflibercept Faricimab in selected settings  Treatment generally follows OCT-guided disease activity.

Photodynamic Therapy PDT was historically used for CNV associated with pattern dystrophy. Today it has largely been replaced by: Anti-VEGF therapy because anti-VEGF generally provides better anatomic and visual outcomes.

Monitoring Patients without complications may be reviewed: Approximately annually depending on:  Age Phenotype Visual symptoms Degree of atrophy

Home Monitoring Patients should be advised to report:  New distortion New central blur New scotoma  An: Amsler grid may be useful for home monitoring.

Low-Vision Rehabilitation Referral is appropriate when central atrophy causes:  Reading difficulty Reduced contrast sensitivity Loss of useful central vision

Genetic Counseling Counseling should address:  Autosomal dominant inheritance in many PRPH2 cases Variable expression Incomplete penetrance in some families Mitochondrial inheritance when MIDD is present

Prognosis Overall visual prognosis is generally: Good Most patients retain useful central vision for many years. Many maintain:  Reading vision Functional independence  into late adulthood.

Poorer Prognostic Factors More significant visual loss occurs with:  Extensive RPE atrophy Foveal photoreceptor loss MNV/CNV Recurrent macular hemorrhage

Complications Important complications include:  Progressive central visual loss RPE atrophy Photoreceptor loss Central scotoma Macular neovascularization Subretinal hemorrhage

Ophthalmology Pearls  Pattern dystrophy is a group of inherited macular RPE disorders characterized by patterned lipofuscin and pigment deposition. Most classic cases are autosomal dominant and associated with PRPH2, formerly called RDS/peripherin. The phenotype can change with age and may differ between the two eyes or among members of the same family. Important patterns include butterfly, reticular, adult-onset vitelliform, fundus pulverulentus, and multifocal pattern dystrophy. OCT commonly shows subretinal or RPE-level hyperreflective material with outer retinal disruption. FAF is often hyperautofluorescent early from lipofuscin accumulation and becomes hypoautofluorescent where RPE atrophy develops. Full-field ERG is usually normal, reflecting the predominantly macular nature of the disease. MIDD should be considered when pattern dystrophy accompanies diabetes and sensorineural deafness, particularly with maternal inheritance. Pattern dystrophy can mimic AMD, Stargardt disease, and Best disease. Most patients retain useful vision for decades. The major treatable complication is macular neovascularization, for which intravitreal anti-VEGF is first-line therapy. New metamorphopsia, hemorrhage, or sudden visual loss should prompt urgent OCT assessment for MNV/CNV.

Ophthalmology – Papilledema in Children

Basics

Description

Papilledema in children is optic disc swelling caused specifically by elevated intracranial pressure (ICP).

It is usually:

• Bilateral
• Relatively symmetric

but may be:

• Markedly asymmetric
• Rarely apparently unilateral

Papilledema is a sign of raised ICP, not a diagnosis itself.

In children, important causes include:

• Hydrocephalus
• Brain tumor
• Cerebral venous sinus thrombosis
• Meningitis
• Craniosynostosis
• Shunt malfunction
• Idiopathic intracranial hypertension (IIH)

Important Pediatric Principle

In young infants:

Markedly elevated ICP may occur without papilledema

because:

• Cranial sutures remain open
• Fontanelles can expand
• Head circumference may increase rather than pressure being transmitted fully to the optic nerve

Therefore:

Absence of papilledema does not exclude raised ICP in infants or young children.

Epidemiology

The incidence of pediatric papilledema depends on the underlying cause.

Common settings include:

• Hydrocephalus
• Brain tumors
• Craniosynostosis
• Cerebral venous sinus thrombosis
• IIH

Pediatric IIH differs from adult disease.

Pediatric IIH Demographics

Prepubertal Children

There is:

• Less female predominance
• Weaker association with obesity

Postpubertal Adolescents

The pattern becomes more similar to adults:

• Female predominance
• Stronger association with obesity and weight gain

Risk Factors

Risk factors for raised ICP in children include:

• Hydrocephalus
• Ventricular shunts
• Brain tumors
• Head trauma
• Craniosynostosis
• Severe intracranial hemorrhage
• Cerebral venous sinus thrombosis

Risk Factors for Pediatric IIH

Associations include:

• Obesity, especially after puberty
• Recent weight gain
• Obstructive sleep apnea
• Certain medications

Medications associated with intracranial hypertension include:

• Tetracyclines
• Vitamin A derivatives / systemic retinoids
• Growth hormone
• Steroid withdrawal
• Lithium in selected cases

The offending medication should be discontinued when clinically appropriate.

Pathophysiology

Elevated ICP is transmitted through the optic nerve subarachnoid space.

This causes:

Increased retrolaminar pressure → impaired axoplasmic transport → optic disc edema

As swelling progresses:

• Venous congestion develops
• Axons become compressed
• Retinal hemorrhages may occur

With prolonged disease:

• Retinal ganglion cell axons are lost
• Optic atrophy develops
• Permanent visual loss may result

Etiology

Important causes include:

• Hydrocephalus
• Brain tumor
• Cerebral venous sinus thrombosis
• Meningitis
• Encephalitis
• Intracranial hemorrhage
• Cerebral edema
• Craniosynostosis
• Shunt malfunction
• IIH

Rare causes include:

• Spinal tumors
• Craniocervical junction lesions
• Severe venous outflow obstruction

Hydrocephalus

Hydrocephalus is an important pediatric cause of papilledema.

It may result from:

• Obstruction of CSF flow
• Impaired CSF absorption
• Congenital abnormalities
• Tumors
• Hemorrhage
• Infection

Children with a ventricular shunt remain at risk for:

Shunt malfunction and recurrent elevated ICP

Brain Tumors

Infratentorial tumors are particularly likely to cause raised ICP because they may obstruct:

• Fourth ventricle
• Cerebral aqueduct
• CSF pathways

Symptoms may include:

• Morning headache
• Vomiting
• Ataxia
• Cranial nerve palsies

Craniosynostosis

Premature fusion of cranial sutures may restrict skull growth and produce:

• Elevated ICP
• Papilledema
• Optic atrophy
• Permanent visual loss

Children with syndromic craniosynostosis require long-term ophthalmic monitoring.

Idiopathic Intracranial Hypertension

Pediatric IIH is raised ICP without:

• Intracranial mass
• Hydrocephalus
• Cerebral venous thrombosis
• Abnormal CSF composition
• Another identifiable secondary cause

It was historically termed:

Pseudotumor cerebri

History

Ask about:

• Headache
• Vomiting
• Transient visual obscurations
• Diplopia
• Pulsatile tinnitus
• Visual loss
• Medication exposure
• Recent weight gain
• Shunt history
• Head trauma
• Fever
• Neurologic symptoms

Headache

Concerning headache features include:

• Awakening from sleep
• Present on awakening
• Progressive severity
• Worsened by coughing or Valsalva
• Associated vomiting
• Associated diplopia

In a child with known hydrocephalus or a ventricular shunt, a new headache should raise concern for:

Shunt dysfunction or recurrent elevated ICP

Infants and Preverbal Children

They may not report headache.

Possible manifestations include:

• Irritability
• Lethargy
• Somnolence
• Poor feeding
• Vomiting
• Developmental regression
• Increasing head circumference
• Bulging fontanelle
• Abnormal eye movements

Transient Visual Obscurations

Children may report:

• Brief blackouts
• Graying of vision
• Momentary blur

usually lasting:

Seconds

These may occur repeatedly and are often provoked by:

• Standing
• Bending
• Position changes

Diplopia

Diplopia most commonly results from:

Sixth nerve palsy

which may be:

• Unilateral
• Bilateral

In younger children, CN VI palsy may present as:

• New esotropia
• Head turn
• Failure to abduct one or both eyes

Visual Acuity

In early papilledema:

Central visual acuity may remain normal

This is an important distinction from many other optic neuropathies.

Once significant visual acuity loss develops, axonal injury may already be substantial.

Color Vision

Color vision is often preserved early.

Loss of color vision suggests:

• Progressive optic nerve dysfunction
• Axonal injury
• More advanced disease

Pupils

Pupils are often normal early.

A RAPD may occur when optic nerve damage is:

• Asymmetric
• Advanced

Fundus Findings

Typical findings include:

• Swollen optic discs
• Blurred disc margins
• RNFL edema
• Loss of physiologic cup
• Obscuration of vessels crossing the disc margin
• Venous engorgement

Disc Hemorrhages

More severe papilledema may cause:

• Peripapillary flame hemorrhages
• Disc hemorrhages
• Cotton-wool spots

Spontaneous Venous Pulsation

Visible spontaneous venous pulsation makes markedly raised ICP less likely.

However:

Absence of venous pulsation is not diagnostic, because it is absent in some normal individuals.

This sign should not be used alone to exclude or confirm intracranial hypertension.

Paton Lines

Paton lines are concentric peripapillary retinal folds caused by optic disc swelling.

They support the presence of significant true disc edema.

Visual Fields

When children are old enough to perform reliable testing, common abnormalities include:

• Enlarged blind spot
• Nasal defects
• Arcuate defects
• Peripheral constriction

Advanced disease can produce:

• Severe generalized field loss
• Central visual loss

Automated Perimetry in Children

Standard automated visual fields may be difficult in young children.

Reliability improves with:

• Age
• Practice
• Shorter strategies
• Experienced pediatric technicians

Children younger than approximately school age may require alternative functional assessment.

Chronic Papilledema

Long-standing papilledema can produce:

• Disc pallor
• RNFL thinning
• Gliosis
• Optic atrophy
• Permanent visual field loss

An atrophic optic nerve may no longer swell significantly even if ICP rises again.

Therefore:

Absence of recurrent papilledema does not reliably exclude shunt malfunction in an optic nerve that is already atrophic.

Diagnostic Approach

The evaluation should answer:

1. Is the disc truly swollen?
2. Is the swelling due to raised ICP?
3. What is causing the raised ICP?

Neuroimaging

Urgent neuroimaging is required for suspected papilledema.

Preferred imaging is:

MRI brain with and without contrast

plus:

MR venography

when feasible.

Why MRV Matters

MRV helps exclude:

Cerebral venous sinus thrombosis

which can occur in children and may mimic IIH.

Risk factors include:

• Dehydration
• Infection
• Inflammatory disease
• Hypercoagulable states
• Malignancy

CT

CT may be appropriate when:

• MRI is unavailable
• Emergency imaging is needed
• Hydrocephalus or mass effect must be assessed rapidly

However, MRI gives superior evaluation of:

• Posterior fossa
• Venous sinuses
• Infiltrative lesions
• Craniovertebral junction

MRI Findings of Raised ICP

Supportive but nonspecific signs include:

• Empty or partially empty sella
• Enlarged perioptic CSF spaces
• Optic nerve tortuosity
• Posterior globe flattening
• Optic disc protrusion
• Venous sinus stenosis

These findings support but do not independently establish IIH.

Lumbar Puncture

After neuroimaging excludes a dangerous mass lesion or obstructive process, LP may be performed.

Evaluate:

• Opening pressure
• CSF cell count
• Protein
• Glucose
• Additional studies as indicated

Pediatric Opening Pressure

In children, an opening pressure of approximately:

≥28 cm H₂O

is generally considered elevated when measured correctly.

A lower threshold around:

≥25 cm H₂O

may be appropriate in a child who is:

• Not obese
• Not sedated

Clinical interpretation is essential.

Proper LP Technique

Opening pressure should ideally be measured:

• In lateral decubitus position
• With the child relaxed
• Without excessive Valsalva
• Without excessive hip flexion

Sedation can influence measurements.

A single borderline number should not override the overall clinical picture.

OCT

OCT is increasingly valuable in pediatric papilledema.

Assess:

• Peripapillary RNFL
• Optic nerve head volume
• Macular ganglion cell layer

OCT Interpretation

Active papilledema causes:

RNFL thickening

As edema improves:

• RNFL thickness falls

However, a fall in RNFL can represent either:

• Resolution of edema
• Axonal loss

Therefore correlate with:

• Ganglion cell layer
• Visual acuity
• Visual fields

Optic Disc Drusen

The most important cause of pediatric pseudopapilledema is:

Optic disc drusen

Children often have:

• Buried drusen
• Elevated disc appearance
• Indistinct margins

without true increased ICP.

Enhanced-Depth OCT

EDI-OCT can help identify:

• Buried optic disc drusen
• Hyperreflective calcified deposits

It is increasingly preferred over older ultrasound-only approaches.

B-Scan Ultrasonography

B-scan may demonstrate:

• Highly reflective calcified optic disc drusen
• Optic nerve sheath enlargement

It remains useful when the diagnosis is uncertain.

Fundus Autofluorescence

Superficial optic disc drusen may show:

Autofluorescence

Buried pediatric drusen may be less detectable.

Differential Diagnosis

Important mimics include:

• Optic disc drusen
• Crowded hyperopic discs
• Tilted optic discs
• Myelinated RNFL
• Optic neuritis
• Neuroretinitis
• NAION, rare in children
• Infiltrative optic neuropathy
• Hypertensive optic disc edema

Papilledema vs Pediatric Optic Neuritis

Papilledema

Usually:

• Bilateral
• Central acuity preserved early
• Symptoms of raised ICP
• Enlarged blind spot

Optic Neuritis

More likely:

• Significant acuity loss
• Dyschromatopsia
• RAPD if asymmetric
• Pain with eye movement
• Asymmetric or unilateral disease

Children with MOG-associated optic neuritis may have dramatic bilateral disc swelling, so clinical distinction can occasionally be difficult.

Neuroretinitis

Neuroretinitis typically produces:

• Optic disc edema
• Macular star

with visual loss.

Bartonella is a classic cause.

This differs from papilledema, although severe papilledema can occasionally also produce macular exudates.

Treatment Principles

There is no treatment directed specifically at the swollen optic disc.

Treatment must address:

The underlying cause of raised ICP

while protecting vision.

Hydrocephalus

Treatment may require:

• Ventriculoperitoneal shunt
• Endoscopic third ventriculostomy in selected cases
• Revision of a malfunctioning shunt

Shunt Malfunction

Children with ventricular shunts may develop:

• Headache
• Vomiting
• Lethargy
• Diplopia
• Visual changes

Papilledema may recur, but:

A normal optic disc does not exclude shunt malfunction, especially in infants or children with prior optic atrophy.

Pediatric IIH – Weight Management

In children with obesity, particularly adolescents:

Gradual weight reduction is disease-modifying therapy.

Management should be developmentally appropriate and often involves:

• Pediatrician
• Dietitian
• Endocrinology or obesity specialist

Aggressive calorie restriction is inappropriate in growing children.

Acetazolamide

Acetazolamide is the principal medication used to lower ICP in pediatric IIH.

It works by decreasing:

CSF production

Dosing is weight-based and individualized.

A commonly used starting range is approximately:

15–25 mg/kg/day divided into several doses

with titration according to:

• Response
• Tolerance
• Severity

Higher doses may be used under specialist supervision.

Acetazolamide Adverse Effects

Potential adverse effects include:

• Paresthesias
• Fatigue
• GI symptoms
• Dysgeusia
• Metabolic acidosis
• Electrolyte abnormalities
• Kidney stones

Monitor:

• Electrolytes
• Renal function

when treatment is prolonged or high-dose.

Topiramate

Topiramate may be useful when:

• Headache is prominent
• Weight management is relevant
• Acetazolamide is poorly tolerated

Potential adverse effects include:

• Cognitive slowing
• Paresthesias
• Appetite suppression
• Nephrolithiasis

Rarely it can cause:

Acute bilateral angle closure with myopic shift

Furosemide

Furosemide may be used as:

• Adjunctive therapy
• Alternative when acetazolamide cannot be used

Evidence is weaker than for acetazolamide.

Corticosteroids

Systemic corticosteroids are not routine treatment for pediatric IIH.

They can cause:

• Weight gain
• Systemic toxicity
• Rebound intracranial hypertension during withdrawal

Steroids are reserved for specific underlying inflammatory or mass-related conditions.

Repeated Lumbar Punctures

Older teaching suggested serial LPs as treatment.

Modern practice:

Repeated lumbar punctures are not routine definitive therapy for IIH and are not reliably curative.

CSF is rapidly regenerated.

LP may occasionally be used as a:

• Short-term temporizing measure

while definitive therapy is arranged.

Optic Nerve Sheath Fenestration

ONSF may be considered for:

• Progressive visual field loss
• Severe papilledema
• Failure of medical treatment
• Vision-threatening IIH

It is particularly useful when:

• Vision is the dominant concern

rather than headache.

CSF Diversion

Options include:

• Ventriculoperitoneal shunt
• Lumboperitoneal shunt

VP shunting is often preferred in many centers.

Indications include:

• Progressive visual loss
• Medically refractory ICP elevation
• Fulminant disease

Fulminant Pediatric IIH

Rapidly progressive papilledema with visual loss is an emergency.

Urgent treatment may require:

• ONSF
• CSF diversion

rather than prolonged trials of medication.

Brain Tumor

Management may require:

• Neurosurgical resection
• Oncology treatment
• CSF diversion
• Corticosteroids for tumor-associated vasogenic edema when appropriate

Cerebral Venous Sinus Thrombosis

CVST generally requires:

Anticoagulation

under pediatric neurology/hematology supervision, unless there is a specific contraindication.

Medication-Induced Intracranial Hypertension

Potential offending drugs should be discontinued when possible.

Important examples:

• Tetracyclines
• Isotretinoin/other systemic retinoids
• Growth hormone in selected cases

Do not combine tetracycline-class antibiotics with systemic retinoids because both are associated with intracranial hypertension.

Craniosynostosis

Treatment may require:

• Craniofacial surgery
• Neurosurgical decompression

Ophthalmic follow-up remains important before and after surgery.

Referral

Children with suspected papilledema generally require urgent coordination between:

• Pediatric ophthalmology / neuro-ophthalmology
• Pediatric neurology
• Neurosurgery

Depending on cause:

• Neuro-oncology
• Hematology
• Endocrinology
• Craniofacial surgery

may be required.

Follow-Up

Follow-up frequency depends on:

• Severity of papilledema
• Visual field status
• Underlying diagnosis
• Rate of progression

Vision-threatening disease may require reassessment within:

Days to weeks

Monitoring

Serial ophthalmic examinations should include:

• Visual acuity
• Pupils
• Color vision
• Optic disc examination
• Fundus photography
• OCT
• Visual fields when reliable

Children With Shunts

Periodic ophthalmic surveillance can help detect recurrent elevated ICP.

However:

The eye examination should never be used as the sole test of shunt function.

Papilledema may be absent despite shunt failure.

Resolution of Papilledema

Disc edema may take:

Several weeks

to resolve after ICP has normalized.

Therefore, persistent swelling immediately after successful treatment does not necessarily indicate treatment failure.

Prognosis

When elevated ICP is identified and treated promptly:

Visual prognosis is generally good

Poorer outcomes occur with:

• Severe papilledema
• Delayed diagnosis
• Recurrent raised ICP
• Shunt malfunction
• Fulminant IIH
• Established optic atrophy

Optic Atrophy

Long-standing pressure may cause irreversible:

• RNFL loss
• Optic pallor
• Visual field loss
• Central visual loss

Once optic atrophy occurs:

Normalization of ICP cannot restore lost axons.

Patient and Family Education

Families should understand warning symptoms of recurrent raised ICP:

• New or worsening headache
• Vomiting
• Lethargy
• New strabismus or diplopia
• Transient visual obscurations
• New visual loss
• Seizure
• Behavioral change

Children with shunts require particular vigilance for:

Shunt malfunction

Complications

Potential complications include:

• Permanent visual field loss
• Optic atrophy
• Reduced visual acuity
• CN VI palsy
• Chronic headache

Underlying disease may also produce:

• Neurologic injury
• Seizures
• Hydrocephalus
• Stroke
• Death

Treatment complications include:

• Medication toxicity
• Post-LP headache
• Shunt infection
• Shunt obstruction
• Shunt revision
• ONSF-related diplopia or optic nerve injury

Ophthalmology Pearls

• Papilledema in children = optic disc swelling from elevated intracranial pressure.
• Infants with open sutures or fontanelles may have markedly elevated ICP without papilledema.
• The same is true after severe optic atrophy: a damaged optic nerve may be unable to swell.
• In young children, raised ICP may present with irritability, lethargy, vomiting, increasing head circumference, or new strabismus rather than a verbalized headache.
• Sixth nerve palsy is the classic ocular motor manifestation of raised ICP.
• Early papilledema may have normal visual acuity, whereas pediatric optic neuritis usually causes more prominent acuity and color loss.
• The most important pseudopapilledema mimic is buried optic disc drusen.
• MRI brain plus MRV is preferred when papilledema is suspected and the child is stable enough for MRI.
• Pediatric LP opening pressure around ≥28 cm H₂O is generally considered elevated; interpretation depends on obesity, sedation, and technique.
• In adolescents with obesity and IIH, weight management plus acetazolamide are standard initial treatments.
• Systemic corticosteroids and serial lumbar punctures are not routine long-term therapy for IIH.
• Rapidly progressive visual loss from fulminant IIH requires urgent surgical consideration.
• Papilledema can take weeks to resolve after ICP normalizes.
• In a child with a ventricular shunt, absence of papilledema does not exclude shunt malfunction.

Ophthalmology – Papilledema

Basics

Description

Papilledema is optic disc swelling caused specifically by elevated intracranial pressure (ICP).

It is usually:

• Bilateral
• Relatively symmetric

but may be:

• Markedly asymmetric
• Rarely apparently unilateral

Papilledema is a sign rather than a diagnosis. The underlying cause of raised ICP must be identified.

Clinical Importance

Papilledema may signal a potentially life-threatening disorder, including:

• Intracranial mass lesion
• Cerebral venous sinus thrombosis (CVST)
• Hydrocephalus
• Meningitis or encephalitis
• Intracranial hemorrhage
• Severe cerebral edema

Therefore:

New true papilledema requires urgent neurologic evaluation and neuroimaging.

Papilledema vs Optic Disc Edema

These terms should not be used interchangeably.

Papilledema

Optic disc edema specifically due to:

Raised ICP

Other Causes of Optic Disc Edema

Include:

• Optic neuritis
• NAION
• AAION
• Neuroretinitis
• Infiltrative optic neuropathy
• Compressive optic neuropathy
• Malignant hypertension

Epidemiology

The epidemiology depends on the underlying cause.

A common cause encountered in neuro-ophthalmology is:

Idiopathic intracranial hypertension (IIH)

IIH most commonly affects:

• Women of reproductive age
• Patients with obesity
• Patients with recent weight gain

However, IIH can occur outside this classic demographic.

Pediatric Considerations

Before puberty:

• IIH has less female predominance
• Obesity is a less consistent association

After puberty, the demographic pattern becomes more similar to adults.

Risk Factors for IIH

Important associations include:

• Obesity
• Recent weight gain
• Female sex after puberty
• Obstructive sleep apnea

Drugs associated with intracranial hypertension include:

• Tetracyclines
• Vitamin A derivatives / retinoids
• Growth hormone
• Lithium in selected cases

Medication history should be reviewed carefully.

Risk Factors for CVST

Important risk factors include:

• Pregnancy and postpartum state
• Estrogen-containing contraception
• Hypercoagulable disorders
• Malignancy
• Systemic infection
• Severe dehydration
• Inflammatory disease

CVST may cause:

• Papilledema
• Stroke
• Seizure
• Intracranial hemorrhage

Pathophysiology

Raised CSF pressure is transmitted through the subarachnoid space surrounding the optic nerve.

This causes:

Elevated retrolaminar pressure → impaired axoplasmic transport → axonal swelling

Secondary effects include:

• Venous congestion
• Capillary leakage
• Hemorrhage
• Peripapillary folds

With prolonged disease:

• Axons are lost
• Optic atrophy develops
• Permanent visual loss may occur

Monro-Kellie Principle

Intracranial volume is composed mainly of:

• Brain tissue
• Blood
• CSF

Because the cranial vault is relatively fixed, expansion of one component without adequate compensation can elevate ICP.

Etiology

Important causes include:

• Idiopathic intracranial hypertension
• Cerebral venous sinus thrombosis
• Intracranial mass
• Hydrocephalus
• Meningitis
• Encephalitis
• Intracranial hemorrhage
• Cerebral edema
• Craniosynostosis
• Venous outflow obstruction
• Rare spinal cord or spinal subarachnoid lesions

Idiopathic Intracranial Hypertension

IIH is raised ICP without an identifiable structural, vascular, or CSF cause.

Historically called:

Pseudotumor cerebri

Diagnostic Features of IIH

Typical criteria include:

• Papilledema
• Otherwise normal neurologic examination except possible cranial nerve abnormalities, especially CN VI palsy
• Neuroimaging showing no mass or hydrocephalus
• Normal CSF composition
• Elevated lumbar puncture opening pressure

In adults, an opening pressure around:

≥25 cm H₂O

supports the diagnosis when measured correctly and interpreted in context.

History

Ask about symptoms of:

• Raised ICP
• Underlying neurologic disease
• Venous thrombosis
• Infection

Important symptoms include:

• Headache
• Nausea
• Vomiting
• Pulsatile tinnitus
• Transient visual obscurations
• Diplopia
• Progressive visual loss

Headache

Headache is common but nonspecific.

It may be:

• Daily or near-daily
• Worse on awakening
• Worse when lying flat
• Worse with coughing or Valsalva
• Migraine-like

Importantly:

Headache severity does not reliably predict the severity of papilledema or visual loss.

Pulsatile Tinnitus

A classic symptom is:

Pulse-synchronous whooshing tinnitus

It is thought to relate to turbulent venous flow.

Transient Visual Obscurations

Patients may experience brief episodes of:

• Graying
• Dimming
• Blackout of vision

usually lasting:

Seconds

Often triggered by:

• Standing
• Bending
• Position change

These are strongly associated with optic disc swelling but do not themselves indicate permanent visual loss.

Diplopia

Diplopia most commonly results from:

Sixth nerve palsy

which may be:

• Unilateral
• Bilateral

CN VI palsy is a classic false-localizing sign of raised ICP.

Visual Acuity

In early papilledema:

Central visual acuity is often normal

Reduced acuity may indicate:

• Advanced papilledema
• Macular edema
• Choroidal folds
• Another optic neuropathy

Color Vision

Usually preserved early.

Progressive dyschromatopsia suggests:

• Optic nerve dysfunction
• Axonal injury
• Advanced disease

Pupils

Pupillary responses are generally normal early.

A RAPD may occur when papilledema or optic nerve injury is:

• Markedly asymmetric

Visual Fields

Early abnormalities commonly include:

• Enlarged blind spot
• Nasal defects
• Arcuate defects

Progressive disease may produce:

• Nasal step
• Peripheral constriction
• Generalized depression
• Central loss in advanced cases

Serial automated perimetry is crucial for monitoring.

Fundus Findings

Early papilledema may show:

• Blurring of disc margins
• RNFL opacification
• Loss of physiologic cup
• Vessel obscuration at the disc edge
• Disc elevation

Spontaneous Venous Pulsation

Loss of spontaneous venous pulsation may occur with elevated ICP.

However:

Absence of spontaneous venous pulsation is not diagnostic, because it may also be absent in normal individuals.

Visible spontaneous venous pulsation makes markedly elevated ICP less likely but does not absolutely exclude it.

Moderate Papilledema

More advanced findings include:

• Disc hyperemia
• Increased elevation
• Venous engorgement
• Peripapillary hemorrhages
• Cotton-wool spots
• Hard exudates
• Retinal folds

Paton Lines

Paton lines are concentric folds around the optic nerve caused by mechanical distortion of the peripapillary retina.

They are characteristic of significant optic disc swelling.

Choroidal Folds

Papilledema may produce:

• Horizontal choroidal folds
• Macular folds

These may cause:

• Metamorphopsia
• Reduced visual acuity

Macular Star

Hard exudates may occasionally form a:

Macular star

This may mimic neuroretinitis.

The overall clinical context is important.

Severe Papilledema

Severe disease may produce:

• Extensive hemorrhages
• Subhyaloid hemorrhage
• Vitreous hemorrhage
• Retinal vascular occlusion
• Macular edema

Chronic Papilledema

Long-standing papilledema may eventually lead to:

• Optic disc pallor
• Gliosis
• RNFL thinning
• Permanent visual field loss
• Optic atrophy

An important point:

An atrophic optic nerve may stop swelling even when ICP remains elevated.

Thus, disappearance of disc edema does not always mean successful treatment.

Frisén Grading

Papilledema can be graded using the:

Frisén scale

ranging from:

Grade 0 to Grade 5

It provides a semiquantitative description of disc swelling.

Visual function must still be assessed independently with:

• Acuity
• Visual fields
• OCT

Diagnostic Approach

The evaluation should answer:

1. Is there true optic disc edema?
2. Is it due to raised intracranial pressure?
3. What is causing the raised ICP?

Neuroimaging

Urgent imaging is required before lumbar puncture in most patients with suspected papilledema.

Preferred study:

MRI brain with and without contrast

plus:

MR venography

to evaluate the cerebral venous sinuses.

Why MRV/CTV Is Important

Venous imaging helps exclude:

Cerebral venous sinus thrombosis

which may closely mimic IIH.

MRV or CTV is especially important when:

• The patient does not fit the classic IIH demographic
• Thrombotic risk factors are present
• Symptoms are acute or atypical

In modern practice, venous imaging is commonly incorporated into the workup of confirmed papilledema.

CT

CT may be used when:

• MRI is unavailable
• Emergency imaging is needed immediately

However, MRI is more sensitive for many structural causes.

MRI Findings Associated With Raised ICP

Supportive but nonspecific findings include:

• Empty or partially empty sella
• Enlarged perioptic CSF spaces
• Optic nerve tortuosity
• Posterior globe flattening
• Optic disc protrusion
• Transverse venous sinus stenosis

These findings support but do not independently establish IIH.

Venous Sinus Stenosis

Transverse sinus stenosis is common in IIH.

It may be:

• A contributor to raised ICP
• A consequence of raised ICP
• Both

Its presence alone is not diagnostic.

Lumbar Puncture

After appropriate imaging has excluded a dangerous mass or obstructive process, LP is performed to assess:

• Opening pressure
• CSF cell count
• Protein
• Glucose
• Additional infectious/inflammatory studies when indicated

Opening Pressure Technique

Opening pressure should ideally be measured:

• In lateral decubitus position
• With the patient relaxed
• Without excessive hip flexion or Valsalva
• Before significant CSF removal

A single pressure reading should always be interpreted in clinical context.

OCT

OCT is extremely useful for monitoring papilledema.

Assess:

• Peripapillary RNFL
• Optic nerve head volume
• Macular ganglion cell layer

Important OCT Principle

In active papilledema:

• RNFL becomes thick

As the edema improves:

• RNFL thickness falls

However, decreasing RNFL may mean either:

• Resolution of edema
• Development of optic atrophy

Therefore, correlate with:

• Ganglion cell analysis
• Visual fields
• Visual acuity

Fundus Photography

Serial disc photographs help document:

• Disc elevation
• Hemorrhages
• Vascular changes
• Treatment response

Optic Disc Ultrasound

B-scan ultrasonography may help distinguish papilledema from:

Optic disc drusen

Other useful modalities include:

• Enhanced-depth imaging OCT
• Fundus autofluorescence

Differential Diagnosis

Important mimics include:

• Optic disc drusen
• Crowded hyperopic discs
• Tilted discs
• Myelinated nerve fibers
• Congenital disc anomalies
• Optic neuritis
• NAION
• AAION
• Neuroretinitis
• Infiltrative optic neuropathy
• Compressive optic neuropathy
• Malignant hypertension

Papilledema vs Optic Disc Drusen

Papilledema favors:

• True edema
• Vessel obscuration
• Hyperemia
• Hemorrhage
• Symptoms of raised ICP

Optic disc drusen favors:

• Lumpy disc surface
• Little hyperemia
• Minimal hemorrhage
• Hyperreflective deposits on OCT
• Autofluorescence if superficial

Buried drusen in children can be particularly difficult to distinguish.

Treatment Principles

Treatment is directed toward:

The cause of intracranial hypertension

while preserving:

• Vision
• Neurologic function
• Life

IIH Treatment Goals

The main goals are:

1. Preserve vision
2. Reduce ICP
3. Treat headache
4. Modify disease risk factors

Weight Loss

For patients with overweight or obesity:

Weight loss is the major disease-modifying treatment for IIH.

Sustained weight reduction may:

• Lower ICP
• Improve papilledema
• Produce remission

Even modest weight loss may help, while greater sustained loss is often needed for durable control.

Bariatric Surgery

For selected patients with:

• Severe obesity
• Persistent IIH
• Inadequate response to conventional weight management

bariatric surgery can produce substantial long-term improvement.

Acetazolamide

Acetazolamide is the principal medication for IIH when papilledema or visual dysfunction is present.

Mechanism:

Decreases CSF production via carbonic anhydrase inhibition

Acetazolamide Dosing

Dose is individualized according to:

• Disease severity
• Visual field loss
• Tolerance

Treatment often begins with a modest dose and is increased as needed.

Acetazolamide Adverse Effects

Common adverse effects include:

• Paresthesias
• Fatigue
• Dysgeusia
• GI upset
• Kidney stones
• Metabolic acidosis
• Electrolyte abnormalities

Monitor:

• Renal function
• Electrolytes

when clinically appropriate.

Topiramate

Topiramate may help because it can:

• Treat migraine-type headache
• Promote weight loss
• Produce mild carbonic anhydrase inhibition

Potential adverse effects include:

• Cognitive slowing
• Paresthesias
• Mood change
• Nephrolithiasis

It can rarely cause:

Acute bilateral angle closure with myopic shift

Furosemide

May occasionally be used as an adjunct when:

• Acetazolamide is not tolerated
• Additional ICP reduction is required

Evidence is less robust.

Corticosteroids

Corticosteroids are not routine long-term treatment for IIH.

They may:

• Cause weight gain
• Produce systemic toxicity
• Cause rebound raised ICP during withdrawal

They remain useful for selected underlying causes such as:

• Vasogenic edema from certain brain tumors
• Inflammatory CNS disease

Serial Lumbar Punctures

Repeated LPs are not recommended for routine long-term treatment because CSF is rapidly replaced.

They may occasionally be used as a temporary bridge while:

• Definitive treatment is arranged
• Pregnancy limits other options

Fulminant IIH

Fulminant IIH involves:

• Rapidly developing severe papilledema
• Rapid visual deterioration

This is a neuro-ophthalmic emergency.

Urgent treatment may require:

• Optic nerve sheath fenestration
• CSF diversion
• Other rapid ICP-lowering intervention

Optic Nerve Sheath Fenestration

ONSF reduces pressure around the optic nerve by creating an opening in the optic nerve sheath.

It is especially considered when:

• Vision is progressively worsening
• Papilledema is severe
• Medical treatment is insufficient
• Headache is not the dominant problem

ONSF Complications

Potential complications include:

• Diplopia
• Optic nerve injury
• Vascular injury
• Visual loss
• Recurrence of papilledema

CSF Diversion

Options include:

• Ventriculoperitoneal shunt
• Lumboperitoneal shunt

VP shunts are commonly favored in many centers.

Indications include:

• Progressive visual loss
• Medically refractory disease
• Fulminant IIH

Shunt Complications

Include:

• Obstruction
• Infection
• Migration
• Overdrainage
• Low-pressure headache
• Need for revision

Venous Sinus Stenting

Venous sinus stenting may be considered for selected patients with:

• Medically refractory IIH
• Significant venous sinus stenosis
• Demonstrable trans-stenotic pressure gradient
• Appropriate neurointerventional evaluation

It should not be performed simply because MRV shows sinus narrowing.

CVST Treatment

Cerebral venous sinus thrombosis generally requires:

Systemic anticoagulation

with management by:

• Neurology/stroke team
• Hematology when appropriate

Intracranial Mass

Treatment may include:

• Neurosurgery
• Oncology therapy
• Corticosteroids for vasogenic edema when appropriate
• CSF diversion

depending on etiology.

Meningitis

Requires urgent cause-specific antimicrobial treatment.

Papilledema in suspected meningitis increases concern about raised ICP and the safety of immediate lumbar puncture.

Pregnancy

IIH may occur or recur during pregnancy.

Management balances:

• Maternal vision
• Maternal health
• Fetal safety

Acetazolamide During Pregnancy

Older teaching recommended complete avoidance.

Modern practice is more individualized.

Acetazolamide is often:

• Avoided when possible during the first trimester
• Considered later, or earlier in vision-threatening disease, when benefits outweigh potential fetal risks

Care should be coordinated with:

• Obstetrics
• Neurology
• Neuro-ophthalmology

Surgical Treatment in Pregnancy

When vision is threatened, options may include:

• Optic nerve sheath fenestration
• CSF diversion
• Temporary lumbar puncture

depending on severity and gestational considerations.

Follow-Up

Follow-up frequency depends on:

• Frisén grade
• Visual field status
• Acuity
• Rate of change
• Treatment response

Severe or rapidly progressive disease may require review within:

Days to weeks

Monitoring

At follow-up, assess:

• Visual acuity
• Pupils
• Color vision
• Optic disc appearance
• OCT
• Automated visual fields
• Symptoms

Headache vs Papilledema

Headache and papilledema should be monitored separately.

A patient may have:

• Resolved papilledema
• Persistent migraine-like headache

Persistent headache alone does not necessarily indicate persistent raised ICP.

Patient Education

Patients should seek urgent reassessment for:

• New visual loss
• Increasing transient visual obscurations
• New diplopia
• Severe worsening headache
• Repeated vomiting
• Seizure
• Focal neurologic symptoms

Prognosis

Visual prognosis is generally excellent when:

• Papilledema is mild
• Visual fields are preserved
• The cause is treated promptly

Poor prognostic factors include:

• Severe papilledema
• Delayed treatment
• Rapid progression
• Significant field loss at presentation
• Optic atrophy

Complications

Potential complications include:

• Permanent visual field loss
• Reduced central acuity
• Optic atrophy
• Chronic headache
• Diplopia from CN VI palsy

Treatment-related complications include:

• Acetazolamide toxicity
• Post-LP headache
• CSF leak
• Shunt infection/failure
• ONSF complications
• Venous stent complications

Ophthalmology Pearls

• Papilledema = optic disc edema specifically due to raised intracranial pressure.
• It is usually bilateral but may be markedly asymmetric.
• True papilledema can indicate brain mass, CVST, hydrocephalus, meningitis, or other life-threatening disease.
• Early central acuity may remain normal; visual field testing is often more sensitive to early functional loss.
• The classic early field defect is enlargement of the blind spot.
• Transient visual obscurations, pulsatile tinnitus, and CN VI palsy are classic symptoms/signs of raised ICP.
• Loss of spontaneous venous pulsation is supportive but not diagnostic.
• MRI brain plus MRV/CTV should exclude mass lesion and venous sinus thrombosis before labeling a patient as IIH.
• After appropriate imaging, lumbar puncture confirms opening pressure and normal CSF composition.
• In adults, ≥25 cm H₂O supports elevated opening pressure when measured correctly.
• OCT is useful, but a falling RNFL thickness can reflect either resolution of edema or optic atrophy.
• In IIH, weight loss is the key disease-modifying treatment.
• Acetazolamide is the main medication used to protect vision in IIH.
• Routine long-term corticosteroids and serial lumbar punctures are generally not recommended for IIH.
• Fulminant IIH with rapidly declining vision requires urgent surgical consideration.
• An optic nerve that has become atrophic may stop swelling despite persistent high ICP, so “less swelling” does not always mean recovery.

Ophthalmology – Paget Disease of Bone

Basics

Description

Paget disease of bone is a chronic disorder of focal bone remodeling characterized by:

• Excessive osteoclastic bone resorption
• Compensatory but disorganized osteoblastic bone formation
• Structurally enlarged but mechanically abnormal bone

Affected bone may become:

• Thickened
• Deformed
• Hypervascular
• Fragile

Many patients are asymptomatic.

Potential complications include:

• Bone pain
• Pathologic fracture
• Skeletal deformity
• Osteoarthritis
• Hearing loss
• Cranial nerve compression
• Rare malignant transformation

Important ophthalmic manifestations include:

• Angioid streaks
• Secondary choroidal neovascularization (CNV)
• Compressive optic neuropathy from skull involvement
• Rare orbital involvement by sarcomatous transformation

Epidemiology

Paget disease primarily affects:

• Older adults
• Usually patients >50 years

Prevalence rises with age.

It is more common in:

• People of European ancestry
• Historically, populations from the United Kingdom and other regions with British ancestry

Its prevalence has declined in many countries over recent decades.

Risk Factors

The cause is incompletely understood.

Risk factors include:

• Increasing age
• Family history
• Genetic susceptibility
• Geographic and ethnic background

Older hypotheses proposed chronic viral infection as a trigger, but a specific viral cause has not been established.

Genetics

Familial disease occurs in a minority of patients.

The best-known gene association is:

SQSTM1

which may produce autosomal dominant familial Paget disease with variable penetrance.

Other genes affecting osteoclast biology have also been identified.

Pathophysiology

Paget disease usually progresses through phases:

Osteolytic Phase

Excessive osteoclastic bone resorption.

Mixed Phase

Simultaneous increased:

• Osteoclastic resorption
• Osteoblastic bone formation

Sclerotic / Burned-Out Phase

Predominantly disorganized bone formation.

The resulting bone has:

• Abnormal architecture
• Increased vascularity
• Reduced mechanical strength

Histopathology

The classic pathologic finding is:

Mosaic pattern of lamellar bone

with irregular cement lines.

There may also be:

• Marrow fibrosis
• Increased local blood flow
• Increased osteoblastic and osteoclastic activity

Commonly Affected Bones

Paget disease commonly affects:

• Pelvis
• Spine
• Femur
• Skull
• Tibia

Less commonly:

• Humerus
• Clavicle

Disease may be:

• Monostotic
• Polyostotic

Skull Involvement

Pagetic skull disease may cause:

• Enlarged head
• Frontal bossing
• Headache
• Hearing loss
• Cranial neuropathies
• Rare optic nerve compression

Skull involvement is particularly relevant to ophthalmology.

Hearing Loss

Hearing impairment is one of the classic complications of skull Paget disease.

Mechanisms may include:

• Abnormal temporal bone remodeling
• Ossicular dysfunction
• Cochlear or neural involvement

Ocular Manifestations

The major ocular associations include:

• Angioid streaks
• CNV
• Subretinal hemorrhage
• Optic neuropathy
• Rare orbital sarcoma

Angioid Streaks

Angioid streaks are:

Crack-like breaks in an abnormal, calcified, or brittle Bruch membrane

They appear as:

• Irregular
• Reddish-brown to gray
• Radiating lines extending from the optic disc

They are usually:

• Bilateral
• Asymmetric

Pathophysiology of Angioid Streaks

In Paget disease, systemic abnormalities in connective tissue and mineralization can produce:

Thickening and fragility of Bruch membrane

Breaks then develop in Bruch membrane and may extend outward from the optic nerve.

Other Associations of Angioid Streaks

Important associations include:

• Pseudoxanthoma elasticum
• Paget disease
• Sickle cell disease and other hemoglobinopathies
• Occasionally other connective tissue disorders
• Idiopathic cases

The classic mnemonic PEPSI is historically used, but pseudoxanthoma elasticum is the strongest systemic association.

Fundus Appearance

Angioid streaks may appear:

• Dark red
• Brown
• Gray

and radiate outward from the optic nerve.

Associated findings may include:

• RPE mottling
• RPE atrophy
• Focal pigment clumping

Peau d’Orange

Peau d’orange refers to a mottled orange-peel appearance of the temporal or midperipheral fundus.

It is more classically associated with:

Pseudoxanthoma elasticum

and may coexist with angioid streaks.

It is not specific for Paget disease.

Choroidal Neovascularization

The most important vision-threatening complication of angioid streaks is:

Choroidal neovascularization

CNV can develop through breaks in Bruch membrane.

Symptoms include:

• Metamorphopsia
• Central blur
• Central scotoma
• Sudden visual loss

Subretinal Hemorrhage

Because Bruch membrane is fragile, even relatively minor ocular trauma may cause:

• Choroidal rupture
• Subretinal hemorrhage

Patients with angioid streaks should therefore avoid significant ocular trauma.

Compressive Optic Neuropathy

Severe skull involvement may rarely cause:

• Optic canal narrowing
• Optic nerve compression

Clinical findings may include:

• Decreased visual acuity
• Dyschromatopsia
• RAPD
• Visual field loss
• Optic atrophy

This is an uncommon but important neuro-ophthalmic complication.

Orbital Sarcoma

Pagetic bone has an increased risk of malignant transformation.

Rare orbital or craniofacial tumors may include:

• Osteosarcoma
• Other sarcomas

Warning features include:

• New severe bone pain
• Rapidly enlarging mass
• New proptosis
• Cranial neuropathy
• Sudden worsening of previously stable symptoms

Associated Systemic Conditions

Complications of extensive disease may include:

• Secondary osteoarthritis
• Pathologic fractures
• Spinal stenosis
• Nerve compression
• Hearing loss
• High-output cardiac failure in very extensive active disease
• Rare osteosarcoma

History

Many patients are asymptomatic and are diagnosed after:

• Elevated alkaline phosphatase
• Incidental abnormal radiograph

When symptomatic, ask about:

• Bone pain
• Fractures
• Hearing loss
• Headache
• Increased hat size
• Bowing of long bones
• Back pain
• Weakness or numbness

Ophthalmic History

Ask about:

• Decreased central vision
• Metamorphopsia
• Scotoma
• Sudden visual decline
• Previous subretinal hemorrhage
• Ocular trauma

These symptoms raise concern for:

CNV or choroidal rupture

Physical Examination

Systemic findings may include:

• Enlarged skull
• Frontal bossing
• Tibial bowing
• Skeletal deformity
• Warmth over active pagetic bone

Neurologic examination should assess for:

• Hearing impairment
• Cranial neuropathies
• Spinal cord or nerve-root compromise

Ophthalmic Examination

Evaluate:

• Visual acuity
• Pupils
• Color vision
• Amsler grid
• Dilated fundus
• Macula
• Optic nerve

Look for:

• Angioid streaks
• RPE changes
• Subretinal hemorrhage
• CNV
• Optic atrophy

Laboratory Testing

The most useful laboratory marker is:

Serum total alkaline phosphatase (ALP)

It is usually elevated when disease is metabolically active and sufficiently extensive.

Alkaline Phosphatase

ALP is useful for:

• Diagnosis
• Assessing disease activity
• Monitoring response to treatment

However, ALP may be normal in:

• Limited monostotic disease
• Inactive disease

If liver disease may confound interpretation, bone-specific ALP can be helpful.

Calcium and Phosphate

Serum:

• Calcium
• Phosphate

are usually normal.

Hypercalcemia should prompt consideration of:

• Prolonged immobilization
• Hyperparathyroidism
• Another metabolic disorder

rather than being attributed automatically to Paget disease.

Vitamin D

Before bisphosphonate therapy, assess and correct:

• Vitamin D deficiency
• Hypocalcemia

because antiresorptive therapy may precipitate or worsen hypocalcemia.

Renal Function

Check renal function before IV bisphosphonate therapy.

Significant renal impairment may limit use of:

Zoledronic acid

Imaging

Plain Radiography

Typical radiographic findings include:

• Cortical thickening
• Bone enlargement
• Coarse trabeculation
• Mixed lytic and sclerotic change

In the skull, a classic late appearance is:

“Cotton wool” skull

Bone Scan

Radionuclide bone scintigraphy is highly sensitive for determining:

• Extent of skeletal involvement
• Distribution of active disease

Pagetic lesions show:

Increased tracer uptake

CT and MRI

CT or MRI is useful when evaluating:

• Neurologic compression
• Optic canal involvement
• Suspected sarcoma
• Spinal stenosis
• Skull-base disease

They are not routinely needed for uncomplicated disease.

Ophthalmic Imaging

Optical Coherence Tomography

OCT is essential when CNV is suspected.

It can demonstrate:

• Subretinal fluid
• Intraretinal fluid
• Pigment epithelial detachment
• Subretinal hyperreflective material

Fluorescein Angiography

FA may help demonstrate:

• CNV leakage
• Lesion extent

It is less routinely required when OCT clearly establishes active CNV.

OCT Angiography

OCTA may demonstrate:

• Neovascular vascular networks

without dye injection.

It may assist with:

• Diagnosis
• Follow-up

but structural OCT remains essential for activity assessment.

Differential Diagnosis

Important systemic differentials include:

• Osteomalacia
• Hyperparathyroidism
• Vitamin D deficiency
• Bone metastasis
• Multiple myeloma
• Fibrous dysplasia
• Osteosarcoma

Differential Diagnosis of Angioid Streaks

Consider:

• Pseudoxanthoma elasticum
• Sickle cell disease
• Other hemoglobinopathies
• Idiopathic angioid streaks
• Choroidal rupture

Treatment Principles

Treatment of Paget disease is aimed at:

• Suppressing excessive bone turnover
• Relieving bone pain
• Preventing or treating complications

Not every asymptomatic patient requires treatment.

Bisphosphonates

Bisphosphonates are the main treatment.

They inhibit:

Osteoclast-mediated bone resorption

Zoledronic Acid

For most patients requiring treatment, the preferred regimen is:

Zoledronic acid 5 mg IV as a single infusion

It usually produces:

• Rapid biochemical remission
• Prolonged suppression of disease activity
• Durable symptom control

It is generally more effective than older oral regimens.

Indications for Treatment

Treatment is generally considered for:

• Symptomatic active disease
• Significant bone pain attributable to Paget disease
• Neurologic complications
• Active disease at sites where progression could cause complications
• Hypercalcemia related to immobilization in active disease
• Before selected orthopedic procedures involving highly active pagetic bone

Treatment decisions should be individualized.

Oral Bisphosphonates

Alternatives when IV zoledronic acid is unsuitable include:

• Risedronate
• Alendronate

They are effective but generally produce less durable remission than zoledronic acid.

Calcitonin

Calcitonin is now:

Rarely used

It may be considered when bisphosphonates are contraindicated or not tolerated.

Bisphosphonate Adverse Effects

Potential adverse effects include:

• Acute flu-like reaction after IV infusion
• Hypocalcemia
• Renal toxicity
• Musculoskeletal pain
• Esophagitis with oral agents
• Rare osteonecrosis of the jaw
• Rare atypical femoral fracture with prolonged exposure

Ocular inflammatory reactions such as:

• Uveitis
• Episcleritis
• Scleritis

are uncommon but recognized.

Oral Bisphosphonate Administration

Oral agents should usually be taken:

• First thing in the morning
• With plain water
• On an empty stomach

Patients should remain upright and avoid food or other medication for the recommended interval.

This reduces:

• Esophageal irritation
• Impaired absorption

Calcium and Vitamin D

Adequate:

• Calcium
• Vitamin D

should be ensured before and after bisphosphonate therapy unless contraindicated.

Treatment of Angioid Streaks

There is:

No treatment for angioid streaks themselves

Management focuses on preventing and treating complications.

Treatment of CNV

The modern first-line treatment for CNV associated with angioid streaks is:

Intravitreal anti-VEGF therapy

Examples include:

• Bevacizumab
• Ranibizumab
• Aflibercept
• Faricimab in selected settings

Treatment is guided by:

• OCT activity
• Visual response
• Recurrent fluid or hemorrhage

Historical CNV Treatments

Older therapies such as:

• Thermal laser photocoagulation
• Photodynamic therapy

have largely been replaced by anti-VEGF because they generally provide inferior visual outcomes or have more limited indications.

Amsler Grid Monitoring

Patients with angioid streaks can use an:

Amsler grid

to detect:

• New metamorphopsia
• New central scotoma

Any new distortion should prompt urgent retinal evaluation.

Protective Eyewear

Because Bruch membrane is fragile, recommend:

Protective eyewear for activities with risk of ocular trauma

This may reduce the risk of traumatic:

• Choroidal rupture
• Subretinal hemorrhage

Optic Neuropathy Management

If visual loss is suspected to result from optic canal compression:

• Obtain orbital/skull imaging
• Coordinate with neurology/neurosurgery/endocrinology or metabolic bone specialists as appropriate
• Treat active Paget disease

Decompressive surgery is reserved for carefully selected cases.

Orthopedic Surgery

Surgery may be required for:

• Severe osteoarthritis
• Fracture
• Major deformity
• Spinal stenosis

Historically, pretreatment of active Paget disease with bisphosphonate was used to reduce surgical blood loss, but evidence for routine preoperative treatment solely for this purpose is limited.

Referral

Consider referral to:

• Endocrinology or metabolic bone specialist
• Ophthalmology/retina
• Neuro-ophthalmology
• Orthopedics
• Neurosurgery

depending on complications.

Follow-Up

Monitor according to:

• Symptoms
• Disease activity
• Treatment response

Serum ALP is commonly rechecked after therapy to document biochemical response.

Once remission is achieved, monitoring intervals can be lengthened.

Ophthalmic Follow-Up

Patients with angioid streaks should undergo periodic:

• Dilated retinal examination
• OCT when symptoms or macular changes arise

Closer follow-up is required after:

• CNV
• Subretinal hemorrhage
• Anti-VEGF therapy

Prognosis

Most patients with Paget disease have:

Good overall prognosis

when complications are recognized and treated.

Visual prognosis depends primarily on:

• Development of CNV
• Macular scarring
• Subretinal hemorrhage
• Optic nerve compression

Malignant Transformation

Malignant transformation is:

Rare

but most commonly results in:

• Osteosarcoma

It should be suspected with:

• New severe pain
• Rapidly enlarging mass
• Cortical destruction
• Soft tissue extension

Complications

Systemic complications include:

• Bone pain
• Skeletal deformity
• Fracture
• Secondary osteoarthritis
• Hearing loss
• Spinal stenosis
• Nerve compression
• Rare hypercalcemia
• Rare high-output heart failure
• Rare osteosarcoma

Ocular complications include:

• CNV
• Subretinal hemorrhage
• Macular scar
• Optic neuropathy
• Permanent visual loss

Ophthalmology Pearls

• Paget disease is a disorder of excessive, disorganized bone remodeling in older adults.
• The characteristic laboratory abnormality is elevated serum alkaline phosphatase with usually normal calcium and phosphate.
• The classic histologic appearance is mosaic lamellar bone.
• Skull involvement can cause hearing loss and, rarely, compressive optic neuropathy.
• The most important ocular association is angioid streaks, representing breaks in abnormal Bruch membrane.
• Angioid streaks are usually bilateral, irregular, reddish-brown lines radiating from the optic disc.
• The major vision-threatening complication is choroidal neovascularization.
• New metamorphopsia or central blur in a patient with angioid streaks should prompt urgent OCT for CNV.
• Intravitreal anti-VEGF is the modern first-line treatment for CNV associated with angioid streaks.
• Laser and photodynamic therapy are largely historical or highly selective treatments for angioid-streak CNV.
• Patients with angioid streaks should use protective eyewear because relatively minor trauma may cause choroidal rupture and hemorrhage.
• Zoledronic acid 5 mg IV once is generally the preferred systemic treatment when active Paget disease requires therapy.
• Osteosarcoma transformation is rare but should be suspected with new severe bone pain or a rapidly enlarging mass.

Ophthalmology – Orbital Vascular Tumors and Malformations

Basics

Description

Orbital vascular lesions comprise a heterogeneous group of vascular tumors and vascular malformations involving the orbit, eyelids, and periocular tissues.

Modern terminology separates true vascular tumors from developmental vascular malformations.

Important orbital vascular lesions include:

• Infantile hemangioma
• Cavernous venous malformation — historically “cavernous hemangioma”
• Distensible venous malformation — historically “orbital varix”
• Lymphatic malformation
• Venolymphatic malformation
• Arteriovenous malformation (AVM)
• Solitary fibrous tumor (SFT) — historically including many lesions called hemangiopericytoma

This modern nomenclature is preferable because these lesions differ substantially in:

• Natural history
• Blood flow
• Imaging
• Treatment

Hemodynamic Classification

Orbital vascular malformations can also be considered according to flow characteristics.

No or Minimal Flow

• Lymphatic malformation

Low-Flow

• Venous malformation
• Venolymphatic malformation
• Cavernous venous malformation

High-Flow

• Arteriovenous malformation
• Arteriovenous fistula

Flow characteristics are important when planning:

• Imaging
• Embolization
• Sclerotherapy
• Surgery

Epidemiology

Vascular lesions represent an important proportion of orbital masses.

The typical age of presentation differs by lesion:

• Infantile hemangioma → infancy
• Lymphatic/venolymphatic malformation → childhood
• Distensible venous malformation → childhood to young adulthood
• Cavernous venous malformation → middle adulthood
• Solitary fibrous tumor → usually adulthood
• AVM → variable, often childhood or young adulthood but may present later

Infantile Hemangioma

Description

Infantile hemangioma is a benign vascular tumor of infancy characterized by:

1. Rapid postnatal proliferation
2. Plateau phase
3. Gradual spontaneous involution

It may involve:

• Eyelid
• Anterior orbit
• Deep orbit
• Combined superficial and deep tissues

Natural History of Infantile Hemangioma

Infantile hemangiomas are usually:

• Absent or subtle at birth
• Apparent within the first few weeks of life
• Rapidly proliferative during early infancy

Most growth occurs during approximately the first:

5–6 months of life

followed by stabilization and gradual involution over subsequent years.

Clinical Appearance

Superficial lesions classically appear:

• Bright red
• Lobulated
• “Strawberry-like”

Deep lesions may appear:

• Bluish
• Subcutaneous
• Poorly defined externally

Deep orbital lesions can produce:

• Proptosis
• Globe displacement
• Ptosis

Ophthalmic Importance of Infantile Hemangioma

Periocular hemangiomas may threaten vision through:

• Astigmatism
• Anisometropia
• Occlusion of visual axis
• Ptosis
• Strabismus
• Optic nerve compression in rare extensive lesions

The major pediatric concern is:

Amblyopia

Early refractive assessment is therefore essential.

PHACE Syndrome

Large segmental facial infantile hemangiomas, particularly involving the upper face, may be associated with:

PHACE syndrome

which includes:

• Posterior fossa abnormalities
• Hemangioma
• Arterial cerebrovascular anomalies
• Cardiac abnormalities/coarctation
• Eye abnormalities

Selected infants require:

• MRI/MRA
• Cardiac evaluation
• Multidisciplinary assessment

before systemic beta-blocker therapy.

Kasabach-Merritt Phenomenon

An important correction:

Kasabach-Merritt phenomenon is not a typical complication of ordinary infantile hemangioma.

It is classically associated with:

• Kaposiform hemangioendothelioma
• Tufted angioma

and involves:

• Severe thrombocytopenia
• Consumptive coagulopathy
• Platelet trapping

Pathology of Infantile Hemangioma

Histologically there is:

• Proliferation of capillary-sized vascular channels
• Benign endothelial cells

Infantile hemangiomas characteristically express:

GLUT1

This helps distinguish them from many vascular malformations.

Treatment of Infantile Hemangioma

Observation is appropriate when the lesion:

• Does not threaten vision
• Does not obstruct visual axis
• Does not induce significant astigmatism
• Does not cause major cosmetic or functional deformity

Propranolol

For vision-threatening or otherwise problematic infantile hemangioma:

Oral propranolol is the modern first-line systemic therapy.

It has largely replaced systemic corticosteroids.

It is especially useful for:

• Visual-axis obstruction
• Significant astigmatism
• Large periocular lesions
• Disfiguring lesions
• Rapid proliferation

Propranolol Safety

Before and during treatment consider:

• Cardiac history
• Heart rate
• Blood pressure
• Feeding status
• Risk of hypoglycemia
• Pulmonary disease

Important adverse effects include:

• Bradycardia
• Hypotension
• Bronchospasm
• Hypoglycemia
• Sleep disturbance

Infants should generally receive doses in association with regular feeding.

Topical Timolol

Topical beta-blocker therapy may be useful for:

• Small
• Superficial
• Thin infantile hemangiomas

It is less effective for large deep orbital lesions.

Corticosteroids

Systemic or intralesional corticosteroids are now used much less frequently because propranolol is usually more effective and better tolerated.

They may still have a role in selected patients when beta-blockers are:

• Contraindicated
• Ineffective

Other Hemangioma Treatments

Rarely considered options include:

• Laser therapy for selected superficial residual lesions
• Surgical excision
• Other systemic agents for highly refractory disease

Surgery is usually reserved for:

• Residual deformity
• Well-localized lesions
• Failure of medical treatment
• Diagnostic uncertainty

Cavernous Venous Malformation

Modern Terminology

The lesion historically called:

Cavernous hemangioma of the orbit

is now more appropriately termed:

Cavernous venous malformation (CVM)

It is not a true proliferative hemangioma.

Epidemiology

CVM is one of the most common benign orbital masses in adults.

Typical patient:

• Middle-aged adult
• Female predominance in many series

Clinical Presentation

Usually presents with:

Slowly progressive, painless unilateral proptosis

Other findings may include:

• Globe displacement
• Diplopia
• Optic nerve compression
• Choroidal folds
• Hyperopic shift

Sudden painful enlargement is unusual unless hemorrhage or thrombosis occurs.

Location

Most CVMs are:

Intraconal

often lateral to the optic nerve.

Because they are well circumscribed, they usually displace rather than infiltrate surrounding orbital structures.

Imaging of Cavernous Venous Malformation

CT

Typically demonstrates:

• Round or ovoid mass
• Well-circumscribed margins
• Intraconal location
• Homogeneous or progressively increasing enhancement

MRI

Usually shows:

• T1 iso- to hypointensity
• T2 hyperintensity
• Strong enhancement

A characteristic feature is:

Progressive contrast fill-in on delayed imaging

because of slow blood flow.

Treatment of Cavernous Venous Malformation

Observation is reasonable when:

• Small
• Asymptomatic
• Stable
• Not threatening the optic nerve

Surgical excision is considered for:

• Progressive proptosis
• Visual decline
• Optic nerve compression
• Diplopia
• Significant cosmetic deformity

Because most lesions are encapsulated, complete excision is often possible.

Distensible Venous Malformation / Orbital Varix

Description

An orbital varix is better understood as a:

Distensible venous malformation

consisting of abnormal thin-walled orbital veins that enlarge when venous pressure rises.

Clinical Presentation

Classic presentation:

Intermittent positional proptosis

which worsens with:

• Valsalva
• Coughing
• Straining
• Bending forward
• Jugular compression

The proptosis may disappear when the patient is upright and relaxed.

Complications of Venous Malformations

Potential complications include:

• Thrombosis
• Orbital hemorrhage
• Pain
• Acute proptosis
• Optic nerve compression

Long-standing lesions may cause:

• Orbital bone remodeling

Imaging of Venous Malformation

Dynamic imaging may be required.

CT or MRI can be performed with:

• Valsalva
• Dependent positioning

The lesion may be inconspicuous at rest and enlarge dramatically with venous pressure.

Imaging may demonstrate:

• Dilated venous channels
• Phleboliths
• Thrombosis

Treatment of Venous Malformation

Observation is appropriate for mild disease.

Intervention may be considered for:

• Visual compromise
• Recurrent thrombosis
• Pain
• Significant disfigurement
• Repeated hemorrhage

Options include:

• Surgical excision
• Sclerotherapy
• Endovascular approaches in selected anatomy

Management should be individualized because uncontrolled bleeding can occur.

Lymphatic Malformation

Modern Terminology

The lesion historically called:

Orbital lymphangioma

is now termed:

Lymphatic malformation

or, when both venous and lymphatic components are present:

Venolymphatic malformation

Pathophysiology

These are congenital developmental vascular malformations rather than true tumors.

They may cross normal anatomic boundaries because they are:

• Unencapsulated
• Multiloculated
• Infiltrative

They can involve:

• Eyelid
• Conjunctiva
• Orbit
• Face
• Intracranial regions

Clinical Presentation

Lesions may be present at birth but remain unnoticed until childhood.

They may suddenly enlarge following:

• Upper respiratory infection
• Hemorrhage
• Trauma

Acute Hemorrhage

Intralesional hemorrhage may produce:

• Sudden painful proptosis
• Eyelid swelling
• Motility restriction
• Optic nerve compression

Blood-filled cysts are sometimes called:

“Chocolate cysts”

Imaging of Lymphatic Malformation

MRI is particularly useful.

Typical features include:

• Multiloculated cystic lesion
• Irregular trans-spatial extension
• Minimal internal flow
• Fluid-fluid levels after hemorrhage

Different fluid levels reflect blood products of different ages.

Treatment of Lymphatic / Venolymphatic Malformation

Observation is appropriate if:

• Vision is unaffected
• Proptosis is mild
• There is no significant deformity

Treatment may be required for:

• Optic neuropathy
• Severe proptosis
• Exposure keratopathy
• Recurrent hemorrhage
• Significant disfigurement

Sclerotherapy

Image-guided sclerotherapy is now an important first-line intervention for many macrocystic lesions.

Agents may include, depending on specialist practice:

• Doxycycline
• Bleomycin
• Sodium tetradecyl sulfate
• Other sclerosants

Treatment is usually performed by an experienced:

• Interventional radiologist
• Orbital surgeon
• Multidisciplinary vascular anomalies team

Surgery for Lymphatic Malformation

Complete surgical excision is often difficult because lesions:

• Lack a capsule
• Infiltrate normal orbital tissues
• Cross anatomic compartments

Surgery may therefore involve:

• Debulking
• Removal of accessible cysts
• Treatment of vision-threatening components

Sirolimus

Systemic sirolimus may be useful in selected extensive or refractory venolymphatic malformations, particularly when lesions are:

• Multifocal
• Infiltrative
• Difficult to treat surgically

This usually requires specialist vascular-anomalies management.

Arteriovenous Malformation

Description

An orbital AVM consists of abnormal direct connections between:

• Arteries
• Veins

without an intervening normal capillary bed.

It is a:

High-flow vascular malformation

Clinical Findings

Possible features include:

• Pulsatile proptosis
• Periorbital swelling
• Conjunctival vascular dilation
• Bruit
• Thrill
• Orbital pain
• Elevated IOP
• Optic neuropathy

Some lesions enlarge during:

• Puberty
• Pregnancy
• Trauma

Imaging of AVM

Evaluation may include:

• CTA
• MRA
• Doppler imaging

However, definitive vascular characterization often requires:

Digital subtraction angiography

which identifies:

• Feeding arteries
• Nidus
• Draining veins

Treatment of AVM

Management usually requires a multidisciplinary neurovascular team.

Options include:

• Endovascular embolization
• Surgical excision after embolization
• Combined staged therapy

Simple surgical excision without vascular planning can result in catastrophic hemorrhage.

Solitary Fibrous Tumor

Modern Classification

Many lesions historically diagnosed as:

Hemangiopericytoma

are now classified within the spectrum of:

Solitary fibrous tumor (SFT)

Pathogenesis

SFTs characteristically demonstrate:

NAB2–STAT6 gene fusion

and strong nuclear:

STAT6 immunoreactivity

Clinical Presentation

Usually occurs in adults and presents with:

• Slowly progressive proptosis
• Globe displacement
• Diplopia
• Occasionally pain

These tumors are often:

• Well circumscribed
• Highly vascular

Imaging of Solitary Fibrous Tumor

CT or MRI may show:

• Well-defined lobulated mass
• Strong contrast enhancement
• Flow voids from vascularity

Some lesions may show:

• Infiltrative margins
• Bone remodeling

Pathology of Solitary Fibrous Tumor

Classic microscopic features include:

• Patternless spindle-cell architecture
• Collagenous stroma
• Branching “staghorn” vessels

Immunohistochemistry commonly shows:

• CD34
• Nuclear STAT6

Treatment of Solitary Fibrous Tumor

Primary treatment is:

Complete surgical excision

with negative margins when possible.

Radiotherapy may be considered for selected:

• Incompletely resected
• Recurrent
• Aggressive

tumors.

Prognosis of Solitary Fibrous Tumor

Most orbital SFTs behave indolently, but some can:

• Recur
• Invade locally
• Metastasize

Incomplete excision increases recurrence risk.

Importantly:

Incomplete excision does not itself cause malignant transformation.

Long-term surveillance is necessary because late recurrence may occur.

Associated Syndromes

PHACE

Associated with large segmental:

Infantile hemangiomas

Wyburn-Mason Syndrome

Associated with:

Retinal and intracranial arteriovenous malformations

and may involve orbital vascular abnormalities.

Blue Rubber Bleb Nevus Syndrome

Associated with multiple:

Venous malformations

especially involving:

• Skin
• Gastrointestinal tract

Orbital involvement is uncommon but possible.

Diagnosis

A complete orbital assessment should include:

• Visual acuity
• Pupils
• Color vision
• Visual fields when appropriate
• IOP
• Refraction in children
• Proptosis measurement
• Motility
• Globe displacement
• Slit-lamp examination
• Dilated fundus examination

Fundus Findings

Orbital vascular lesions may produce:

• Choroidal folds
• Optic disc edema
• Optic atrophy
• Venous congestion

depending on mass effect and vascular physiology.

Visual Complications

Visual loss may result from:

• Amblyopia
• Induced astigmatism
• Exposure keratopathy
• Optic nerve compression
• Elevated IOP
• Retinal or choroidal folds
• Orbital hemorrhage

Imaging Principles

MRI

Best for:

• Soft-tissue characterization
• Lymphatic/venolymphatic lesions
• Intracranial extension
• Optic nerve relationship

CT

Best for:

• Bone
• Phleboliths
• Calcification
• Acute hemorrhage in selected cases

Dynamic Imaging

Useful for:

• Distensible venous malformation

Angiography

Particularly important for:

• AVM
• Other high-flow lesions

Biopsy

Biopsy is generally not required for vascular malformations with characteristic imaging.

Avoid unnecessary needle biopsy of suspected high-flow vascular lesions because of:

Hemorrhage risk

Biopsy or excision is appropriate when:

• Diagnosis remains uncertain
• A true neoplasm is suspected
• Malignancy must be excluded

Differential Diagnosis

Important orbital mimics include:

• Thyroid eye disease
• Idiopathic orbital inflammation
• Optic nerve sheath meningioma
• Optic pathway glioma
• Rhabdomyosarcoma
• Lymphoma
• Metastatic tumor
• Dermoid cyst
• Lacrimal gland tumor
• Orbital cellulitis

Treatment Principles

Treatment is determined by:

• Lesion type
• Flow characteristics
• Age
• Visual threat
• Growth
• Cosmetic impact
• Surgical accessibility

Many lesions can be observed if they are:

• Stable
• Asymptomatic
• Not threatening vision

Indications for Treatment

Intervention is particularly appropriate when there is:

• Optic neuropathy
• Amblyopia risk
• Visual-axis obstruction
• Severe astigmatism
• Exposure keratopathy
• Significant proptosis
• Recurrent hemorrhage
• Pain
• Major cosmetic deformity

Follow-Up

Monitoring depends on lesion type.

Assess serially for:

• Visual acuity
• Amblyopia
• Refraction
• Proptosis
• Motility
• Optic nerve function
• Lesion growth
• Recurrent hemorrhage

Imaging is repeated when:

• Clinical findings change
• Growth is suspected
• Treatment response is being assessed

Prognosis

Prognosis varies markedly by lesion.

Infantile hemangioma

Usually excellent, especially when amblyopia is prevented.

Cavernous venous malformation

Excellent after complete excision when treatment is required.

Lymphatic/venolymphatic malformation

Often chronic and recurrent because of infiltrative anatomy.

Venous malformation

Usually benign but may cause recurrent positional symptoms, thrombosis, or hemorrhage.

AVM

Potentially serious because of high-flow vascular physiology and hemorrhage risk.

Solitary fibrous tumor

Usually favorable after complete excision, but requires long-term surveillance.

Complications

Potential complications include:

• Amblyopia
• Astigmatism
• Strabismus
• Ptosis
• Exposure keratopathy
• Optic neuropathy
• Visual field loss
• Elevated IOP
• Hemorrhage
• Thrombosis
• Recurrent proptosis
• Treatment-related bleeding
• Recurrence

Ophthalmology Pearls

• Modern terminology separates vascular tumors from vascular malformations.
• Infantile hemangioma is a true vascular tumor; propranolol is now the major first-line systemic treatment for vision-threatening lesions.
• The main ophthalmic danger from periocular infantile hemangioma is amblyopia from visual-axis obstruction or induced astigmatism.
• Kasabach-Merritt phenomenon is not typical of infantile hemangioma; think kaposiform hemangioendothelioma or tufted angioma.
• “Cavernous hemangioma” is better termed cavernous venous malformation and classically causes slowly progressive painless intraconal proptosis in adults.
• “Orbital varix” is a distensible venous malformation; proptosis characteristically increases with Valsalva or bending forward.
• “Lymphangioma” is better termed lymphatic or venolymphatic malformation.
• Fluid-fluid levels on MRI are classic for hemorrhage within lymphatic/venolymphatic malformations.
• Sclerotherapy is now an important treatment for many macrocystic lymphatic malformations; extensive refractory disease may sometimes require sirolimus.
• AVMs are high-flow lesions and often require angiography plus embolization before surgical treatment.
• “Hemangiopericytoma” of the orbit has largely been reclassified as solitary fibrous tumor, characterized by STAT6 nuclear positivity/NAB2–STAT6 fusion.
• Avoid biopsy of a suspected high-flow orbital vascular lesion without appropriate vascular imaging because of potentially severe hemorrhage.

Medicine – Causes of Hypoparathyroidism

Hypoparathyroidism is an endocrine disorder characterised by deficient secretion or action of parathyroid hormone (PTH). Because PTH is one of the major regulators of calcium and phosphate balance, deficiency of PTH produces the characteristic biochemical combination of:

↓ PTH + ↓ Ca²⁺ + ↑ phosphate.

The major causes include surgical removal or damage to the parathyroid glands, autoimmune destruction, congenital absence or abnormal development of the glands, and genetic disorders affecting PTH production or action.

An important correction to the original notes is that pseudohypoparathyroidism is not true hypoparathyroidism. In pseudohypoparathyroidism, PTH is produced but the target tissues are resistant to its action, so PTH is elevated rather than decreased.

1. Normal Function of PTH

PTH is secreted by the:

Parathyroid glands.

Its secretion is primarily regulated by the concentration of:

Ionised calcium in the blood.

When serum calcium falls:

↓ Ca²⁺

↓

Parathyroid calcium-sensing receptors detect the fall

↓

↑ PTH secretion

↓

Serum calcium is restored toward normal.

2. Major Actions of PTH

PTH acts mainly on:

Bone

and

Kidney.

It also indirectly increases intestinal calcium absorption through activation of:

Vitamin D.

The overall effect is:

↑ Serum calcium

and

↓ Serum phosphate.

Therefore PTH can be remembered as a hormone that:

RAISES CALCIUM AND LOWERS PHOSPHATE.

3. PTH and the Kidney

In the kidney, PTH increases:

Calcium reabsorption, particularly in the distal nephron.

At the same time, PTH decreases:

Phosphate reabsorption in the proximal tubule.

Therefore:

↑ PTH → ↑ urinary phosphate excretion – phosphaturia.

PTH also stimulates renal:

1α-hydroxylase

which converts:

25-hydroxyvitamin D

into:

1,25-dihydroxyvitamin D – calcitriol.

4. PTH and Vitamin D

Calcitriol increases intestinal absorption of:

Calcium

and

Phosphate.

Therefore PTH indirectly supports serum calcium by increasing:

Calcitriol production → intestinal calcium absorption.

When PTH is deficient:

↓ Calcitriol production

contributes to:

Hypocalcaemia.

5. What Happens in Hypoparathyroidism?

When PTH secretion is inadequate:

↓ PTH

↓

↓ Renal calcium reabsorption

• ●

↓ Calcitriol production

↓

↓ Intestinal calcium absorption

↓

Hypocalcaemia.

At the same time:

↓ PTH

↓

Loss of the normal phosphaturic effect

↓

↑ Renal phosphate reabsorption

↓

Hyperphosphataemia.

Therefore the classic biochemical pattern is:

Ca²⁺ ↓

Phosphate ↑

PTH ↓ or inappropriately low.

6. Surgical Hypoparathyroidism

The original notes correctly identify:

Parathyroidectomy

as an important cause.

Hypoparathyroidism can occur when the parathyroid glands are:

Intentionally removed

or

Accidentally damaged, removed or devascularised during neck surgery.

This is one of the most important acquired causes of hypoparathyroidism.

7. Thyroid Surgery

Because the parathyroid glands lie closely related to the posterior surface of the thyroid gland, they may be injured during:

Thyroidectomy.

Possible mechanisms include:

Accidental removal.

Damage to the parathyroid blood supply.

Direct surgical injury.

This can produce postoperative:

Hypocalcaemia.

8. Temporary Versus Permanent Postoperative Hypoparathyroidism

After thyroid or parathyroid surgery, hypoparathyroidism may be:

Temporary

or

Permanent.

Temporary hypocalcaemia can occur because the remaining glands are transiently dysfunctional or their blood supply has been disturbed.

Permanent disease occurs when insufficient functioning parathyroid tissue remains.

Therefore calcium should be monitored carefully following relevant:

Neck surgery.

9. Intentional Parathyroidectomy

Parathyroid tissue may intentionally be removed during treatment of severe:

Primary hyperparathyroidism

or selected cases of severe:

Secondary or tertiary hyperparathyroidism.

Excessive removal can result in:

Hypoparathyroidism and hypocalcaemia.

10. Hungry Bone Syndrome – Important Distinction

Hypocalcaemia after parathyroid surgery does not always mean permanent hypoparathyroidism.

After removal of a source of severe PTH excess, previously high-turnover bone may rapidly take up:

Calcium, phosphate and magnesium.

This is called:

Hungry bone syndrome.

It can produce prolonged postoperative hypocalcaemia.

Therefore:

POST-PARATHYROIDECTOMY HYPOCALCAEMIA

may reflect either:

Low PTH

or

Hungry bone syndrome.

The biochemical patterns help distinguish them.

11. Autoimmune Hypoparathyroidism

The original notes correctly include:

Autoimmune disease.

The immune system can destroy or impair the:

Parathyroid glands.

This produces:

Reduced PTH secretion.

Autoimmune hypoparathyroidism may occur in isolation or as part of a broader:

Autoimmune polyglandular syndrome.

12. Autoimmune Polyglandular Syndrome Type 1

A classic association is:

Autoimmune polyendocrine syndrome type 1 – APS-1, also called APECED.

It is associated with mutations in:

AIRE.

The classic manifestations include:

Chronic mucocutaneous candidiasis.

Hypoparathyroidism.

Primary adrenal insufficiency – Addison disease.

Therefore hypocalcaemia in a patient with other autoimmune endocrine abnormalities should raise consideration of:

Autoimmune hypoparathyroidism.

13. DiGeorge Syndrome

The original notes correctly identify:

DiGeorge syndrome.

DiGeorge syndrome is usually related to:

22q11.2 deletion.

There is abnormal development of structures derived primarily from the:

Third and fourth pharyngeal pouches.

This can lead to abnormal development or absence of:

Parathyroid tissue

and the:

Thymus.

14. Hypocalcaemia in DiGeorge Syndrome

Because parathyroid development is impaired:

↓ Parathyroid tissue

↓

↓ PTH

↓

Hypocalcaemia.

Affected infants may therefore present with:

Tetany

or

Seizures due to hypocalcaemia.

15. Other Features of DiGeorge Syndrome

The phenotype is variable, but important associations include:

Congenital heart disease, particularly conotruncal abnormalities.

Thymic hypoplasia or aplasia with T-cell immune dysfunction.

Characteristic craniofacial/palatal abnormalities.

Hypoparathyroidism with hypocalcaemia.

Therefore a useful association is:

CARDIAC DEFECT + IMMUNE DEFICIENCY + HYPOCALCAEMIA → THINK 22q11.2 DELETION/DIGEORGE SYNDROME.

16. Pseudohypoparathyroidism – Important Correction

The original notes list:

“Receptor defect – pseudohyperparathyroidism.”

The correct term is:

Pseudohypoparathyroidism.

More importantly, pseudohypoparathyroidism is not a cause of true PTH deficiency.

Instead, the body produces PTH, but target tissues have:

Resistance to PTH action.

17. Pseudohypoparathyroidism Mechanism

Because the kidneys do not respond appropriately to PTH:

Renal calcium-conserving/PTH-dependent effects are impaired

and

Phosphate excretion is reduced.

Therefore:

Calcium ↓

Phosphate ↑.

The parathyroid glands detect the low calcium and respond by secreting more PTH.

Therefore:

PTH ↑.

18. Hypoparathyroidism Versus Pseudohypoparathyroidism

This is an extremely important examination distinction.

TRUE HYPOPARATHYROIDISM:

PTH:

↓

Calcium:

↓

Phosphate:

↑

PSEUDOHYPOPARATHYROIDISM:

PTH:

↑

Calcium:

↓

Phosphate:

↑

The difference is therefore:

LOW PTH → true hypoparathyroidism.

HIGH PTH → PTH resistance/pseudohypoparathyroidism, assuming the biochemical and clinical context fits.

19. Albright Hereditary Osteodystrophy

Some forms of pseudohypoparathyroidism are associated with physical features collectively known as:

Albright hereditary osteodystrophy – AHO.

Features can include:

Short stature.

Round face.

Brachydactyly, particularly shortening of selected metacarpals/metatarsals.

Subcutaneous ossification.

The phenotype and hormone resistance depend on the underlying molecular subtype.

20. Genetic Causes of True Hypoparathyroidism

Several inherited disorders can cause genuine:

PTH deficiency.

These may affect:

Parathyroid development

or

PTH synthesis/secretion.

Although individually uncommon, they are particularly important when hypoparathyroidism presents in:

Childhood

or when there is a strong:

Family history.

21. Activating Calcium-Sensing Receptor Disorders

The:

Calcium-sensing receptor – CaSR

helps parathyroid cells determine whether serum calcium is sufficiently high.

Certain activating genetic abnormalities can make the receptor behave as though calcium is higher than it actually is.

Therefore PTH secretion becomes:

Inappropriately suppressed.

This can cause:

Hypocalcaemia with low or inappropriately normal PTH.

Renal calcium loss may also be increased.

22. Severe Hypomagnesaemia – Important Additional Cause

An important cause not included in the original list is:

Severe hypomagnesaemia.

Magnesium is necessary for normal:

PTH secretion

and

PTH action.

Therefore severe magnesium deficiency can cause:

Reduced PTH secretion

and

Peripheral PTH resistance.

23. Magnesium and Refractory Hypocalcaemia

This produces an important clinical pattern:

Hypomagnesaemia

↓

↓ PTH secretion/action

↓

Hypocalcaemia.

Therefore:

HYPOCALCAEMIA THAT DOES NOT CORRECT APPROPRIATELY → CHECK MAGNESIUM.

Calcium may remain difficult to correct until:

Magnesium is replaced.

24. Infiltrative and Destructive Disorders

Rarely, parathyroid tissue can be damaged by infiltrative or destructive processes.

Examples can include:

Iron overload, such as severe haemochromatosis or transfusional iron overload.

Copper deposition in selected circumstances.

Metastatic/infiltrative disease.

These are much less common than:

Surgery or autoimmune disease.

25. Clinical Features

Most symptoms of hypoparathyroidism result from:

Hypocalcaemia.

Low extracellular calcium increases:

Neuromuscular excitability.

Therefore patients can develop:

Perioral tingling.

Paraesthesia.

Muscle cramps.

Carpopedal spasm.

Tetany.

26. Chvostek Sign

Chvostek sign refers to contraction of facial muscles following tapping over the facial nerve.

It may occur with:

Hypocalcaemia.

However, it is not perfectly sensitive or specific and may occasionally be present in people without clinically important hypocalcaemia.

27. Trousseau Sign

Trousseau sign is carpal spasm precipitated by inflation of a blood-pressure cuff above systolic pressure for several minutes.

It reflects increased:

Neuromuscular excitability due to hypocalcaemia.

It is generally a more useful sign of latent tetany than Chvostek sign.

28. Severe Hypocalcaemia

Severe hypocalcaemia can produce:

Tetany.

Laryngospasm.

Bronchospasm.

Seizures.

Altered mental status.

Cardiac electrical abnormalities may also occur.

29. ECG Changes

Hypocalcaemia classically causes:

QT-interval prolongation.

Severe electrolyte disturbance can increase the risk of:

Cardiac arrhythmias.

Therefore symptomatic or severe hypocalcaemia requires prompt assessment and treatment.

30. Chronic Hypoparathyroidism

Longstanding hypoparathyroidism may be associated with:

Cataracts.

Dental abnormalities, particularly when disease begins during development.

Basal ganglia and other intracranial calcification.

Neuropsychiatric symptoms.

Chronic management must also avoid excessive calcium replacement because of the risk of:

Hypercalciuria and renal complications.

31. Diagnosis

The original notes correctly state that true hypoparathyroidism produces:

↓ Calcium

and

↓ PTH.

However, phosphate is also extremely important.

The characteristic pattern is:

Calcium ↓

Phosphate ↑

PTH ↓ or inappropriately normal.

32. Why “Inappropriately Normal” PTH Matters

When calcium is low, normal physiology should produce:

A substantial rise in PTH.

Therefore a PTH concentration that lies technically within the laboratory reference range may still be:

Inappropriately normal.

In a patient with hypocalcaemia, PTH should be elevated.

Thus:

LOW Ca²⁺ + PTH that fails to rise appropriately → suspect hypoparathyroidism.

33. Confirming True Hypocalcaemia

Total serum calcium is affected by:

Albumin concentration.

Therefore calcium assessment may require consideration of:

Albumin-adjusted calcium

or direct measurement of:

Ionised calcium, particularly in selected acute or complex situations.

A low total calcium caused simply by hypoalbuminaemia is not equivalent to true:

Ionised hypocalcaemia.

34. Other Investigations

Evaluation commonly includes:

Calcium.

Phosphate.

PTH.

Magnesium.

Renal function.

25-hydroxyvitamin D.

Depending on the context, urinary calcium and additional genetic or autoimmune investigations may be appropriate.

35. Treatment Principles

Treatment aims to:

Relieve symptomatic hypocalcaemia

while maintaining calcium at a safe level and avoiding excessive:

Urinary calcium excretion.

Management depends on whether hypocalcaemia is:

Acute/severe

or

Chronic.

36. Acute Symptomatic Hypocalcaemia

Severe symptomatic hypocalcaemia may require:

Intravenous calcium, commonly calcium gluconate, with appropriate monitoring.

This is particularly relevant with:

Tetany.

Seizures.

Laryngospasm.

Significant ECG abnormalities.

The underlying cause must simultaneously be addressed.

37. Chronic Hypoparathyroidism

Long-term conventional treatment commonly uses:

Oral calcium

plus:

Active vitamin D, such as calcitriol or an appropriate analogue.

Why active vitamin D?

Because low PTH reduces renal activation of vitamin D.

Therefore providing active vitamin D helps increase:

Intestinal calcium absorption.

38. Correct Magnesium

If magnesium is deficient:

Magnesium must be corrected.

Otherwise PTH secretion and action may remain impaired and the hypocalcaemia may be:

Refractory to calcium treatment.

Therefore:

LOW Ca²⁺ + LOW Mg²⁺ → CORRECT Mg²⁺.

39. Monitoring Chronic Treatment

The objective is not necessarily to push serum calcium to the high-normal range.

Excessive calcium and active vitamin D treatment can produce:

Hypercalciuria.

This can contribute to:

Nephrolithiasis.

Nephrocalcinosis.

Renal impairment.

Therefore serum and urinary calcium require appropriate monitoring during chronic treatment.

40. Causes of Hypoparathyroidism – Note Form

POSTSURGICAL:

Parathyroidectomy.

Accidental parathyroid removal during thyroid surgery.

Parathyroid vascular injury during neck surgery.

AUTOIMMUNE:

Isolated autoimmune hypoparathyroidism.

Autoimmune polyendocrine syndrome type 1 – APECED.

CONGENITAL/GENETIC:

DiGeorge syndrome – 22q11.2 deletion.

Genetic abnormalities of parathyroid development or PTH secretion.

Activating calcium-sensing receptor disorders.

FUNCTIONAL PTH DEFICIENCY:

Severe hypomagnesaemia.

RARE DESTRUCTIVE/INFILTRATIVE CAUSES:

Iron overload and other infiltrative disorders.

41. Pseudohypoparathyroidism – Keep Separate

The original notes place pseudohypoparathyroidism under causes of hypoparathyroidism.

For examination purposes, it is better to keep it separate because:

The parathyroid glands are producing PTH.

The problem is:

Target-organ resistance to PTH.

Therefore:

Ca²⁺ ↓

PO₄³⁻ ↑

but:

PTH ↑.

42. Biochemical Patterns – Note Form

TRUE HYPOPARATHYROIDISM

Calcium:

↓

Phosphate:

↑

PTH:

↓ or inappropriately normal

PSEUDOHYPOPARATHYROIDISM

Calcium:

↓

Phosphate:

↑

PTH:

↑

PRIMARY HYPERPARATHYROIDISM

Calcium:

↑

Phosphate:

↓ or low-normal

PTH:

↑ or inappropriately normal

SECONDARY HYPERPARATHYROIDISM DUE TO VITAMIN D DEFICIENCY

Calcium:

↓ or low-normal

Phosphate:

↓

PTH:

↑

ALP:

↑

SECONDARY HYPERPARATHYROIDISM DUE TO ADVANCED CKD

Calcium:

↓ or normal

Phosphate:

↑

PTH:

↑

43. Important Corrections to the Original Notes

The original:

“Parathyroidectomy – intentional or accidental”

is correct.

Surgery is one of the most important acquired causes of true hypoparathyroidism.

The original:

“Autoimmune”

is also correct.

Remember the association with:

APS-1/APECED → candidiasis + hypoparathyroidism + Addison disease.

The original:

“DiGeorge syndrome”

is correct.

Remember:

22q11.2 deletion → abnormal parathyroid development → ↓ PTH → hypocalcaemia.

The original term:

“pseudo-hyperparathyroidism”

should be corrected to:

PSEUDOHYPOPARATHYROIDISM.

This is PTH resistance, not PTH deficiency.

Therefore:

PTH is HIGH, not low.

The original diagnosis:

↓ Ca²⁺ + ↓ PTH

is correct for true hypoparathyroidism, but add:

↑ PHOSPHATE.

Therefore the complete classic pattern is:

↓ Ca²⁺ + ↑ PO₄³⁻ + ↓ PTH.

Key Clinical Pattern

For rapid recall:

PTH RAISES CALCIUM AND LOWERS PHOSPHATE.

Therefore if PTH disappears:

↓ PTH

↓

↓ Ca²⁺

• ●

↑ PO₄³⁻.

The major causes are:

NECK/PARATHYROID SURGERY + AUTOIMMUNE DESTRUCTION + DiGEORGE/CONGENITAL DISEASE + SEVERE HYPOMAGNESAEMIA.

The most important distinction is:

TRUE HYPOPARATHYROIDISM

Ca ↓ | PO₄ ↑ | PTH ↓

versus:

PSEUDOHYPOPARATHYROIDISM

Ca ↓ | PO₄ ↑ | PTH ↑.

And the classic symptomatic presentation is:

HYPOCALCAEMIA → PERIORAL TINGLING + PARAESTHESIA + CRAMPS + CARPOPEDAL SPASM + TETANY ± SEIZURES, with possible:

PROLONGED QT INTERVAL.

Medicine – Causes of Hyperphosphataemia

Hyperphosphataemia means an abnormally increased concentration of phosphate in the blood. In adults, it is generally defined as a serum phosphate above the laboratory reference range, commonly around:

Serum phosphate >1.45 mmol/L (≈4.5 mg/dL).

Phosphate concentration varies with age, renal function, dietary intake, PTH, vitamin D and cellular metabolism. Children normally have higher phosphate concentrations than adults because of active skeletal growth.

The kidneys are the major regulators of long-term phosphate balance. Therefore, the most important cause of persistent hyperphosphataemia is:

Reduced renal phosphate excretion, particularly in advanced chronic kidney disease.

1. Normal Phosphate Regulation

Most phosphate in the body is stored in:

Bone and teeth.

A smaller proportion is intracellular, while only a very small amount circulates in extracellular fluid.

Serum phosphate is regulated primarily by:

Kidneys.

PTH.

FGF23.

Vitamin D – calcitriol.

Intestinal absorption.

2. Renal Handling of Phosphate

Most filtered phosphate is normally reabsorbed in the:

Proximal renal tubule.

The kidneys can alter phosphate excretion according to the body’s requirements.

Two important hormones promote phosphate excretion:

PTH

and

FGF23.

Therefore:

↑ PTH or ↑ FGF23 → ↓ proximal phosphate reabsorption → ↑ phosphaturia → ↓ serum phosphate.

Conversely, reduced renal function or reduced PTH action can cause:

Phosphate retention → hyperphosphataemia.

3. Major Mechanisms of Hyperphosphataemia

The causes are easiest to understand through four mechanisms:

Reduced renal phosphate excretion.

Increased intestinal phosphate absorption or phosphate administration.

Release of intracellular phosphate into the blood.

Increased renal phosphate reabsorption.

The original causes fit well into these categories.

4. Renal Failure

The original notes correctly identify:

Renal failure

as the most important cause.

More precisely, hyperphosphataemia is particularly associated with:

Advanced chronic kidney disease – CKD.

As GFR declines, the kidneys progressively lose their ability to eliminate the daily phosphate load.

5. Early CKD and Phosphate

An important point is that phosphate does not necessarily rise early in CKD.

Initially, the body compensates by increasing:

FGF23

and

PTH.

These hormones increase phosphate excretion by the remaining functioning nephrons.

Therefore serum phosphate may remain:

Normal during earlier CKD.

6. Advanced CKD

As kidney function deteriorates further, compensation becomes inadequate.

Therefore:

↓ GFR

↓

↓ Filtered phosphate excretion

↓

Phosphate retention

↓

↑ Serum phosphate.

Hyperphosphataemia becomes particularly important in:

Advanced CKD and kidney failure.

7. CKD–Mineral and Bone Disorder

Phosphate retention contributes to:

CKD–mineral and bone disorder – CKD-MBD.

At the same time, diseased kidneys produce less:

Calcitriol – 1,25-dihydroxyvitamin D.

Therefore:

↓ Calcitriol

↓

↓ Intestinal calcium absorption

↓

Tendency toward low/low-normal calcium.

8. Secondary Hyperparathyroidism in CKD

The combination of:

Phosphate retention

• ●

Reduced calcitriol

• ●

Low or low-normal calcium

stimulates the parathyroid glands.

Therefore:

PTH increases.

This produces:

Secondary hyperparathyroidism.

The classic pattern in advanced CKD is therefore:

Phosphate ↑

Calcium ↓ or normal

PTH ↑

ALP may be ↑

9. Why High Phosphate Matters in CKD

Persistent abnormalities of calcium-phosphate metabolism contribute to:

Secondary hyperparathyroidism.

Renal osteodystrophy.

Vascular and soft-tissue calcification.

Cardiovascular disease risk.

Therefore phosphate control is an important component of management in advanced CKD.

10. Hypoparathyroidism

The original notes correctly include:

Hypoparathyroidism.

Normally, PTH promotes:

Renal phosphate excretion.

Therefore:

↓ PTH

↓

↑ Proximal tubular phosphate reabsorption

↓

↓ Urinary phosphate excretion

↓

↑ Serum phosphate.

11. Hypoparathyroidism Pattern

At the same time, loss of PTH reduces mechanisms that normally maintain serum calcium.

Therefore the classic biochemical pattern is:

Calcium ↓

Phosphate ↑

PTH ↓

ALP usually normal.

This is essentially the opposite of the typical pattern in:

Primary hyperparathyroidism.

12. Primary Hyperparathyroidism Versus Hypoparathyroidism

PRIMARY HYPERPARATHYROIDISM:

PTH:

↑

Calcium:

↑

Phosphate:

↓

because PTH causes:

Phosphaturia.

HYPOPARATHYROIDISM:

PTH:

↓

Calcium:

↓

Phosphate:

↑

because renal phosphate excretion decreases.

Therefore:

LOW CALCIUM + HIGH PHOSPHATE → THINK HYPOPARATHYROIDISM, particularly when PTH is low.

13. Acromegaly

The original notes correctly include:

Acromegaly.

Acromegaly results from excessive:

Growth hormone – GH

and consequently increased:

IGF-1.

One effect is increased renal tubular:

Phosphate reabsorption.

Therefore:

GH/IGF-1 excess → ↑ renal phosphate reabsorption → ↑ serum phosphate.

14. Biochemical Clue in Acromegaly

Hyperphosphataemia is not usually the presenting feature of acromegaly, but a mildly elevated phosphate concentration can occur.

The more important diagnostic test is:

Serum IGF-1.

Diagnosis is then confirmed appropriately, often with assessment of GH suppression following an oral glucose load and pituitary imaging.

Therefore phosphate is:

A supportive biochemical association rather than the principal diagnostic marker.

15. Vitamin D Excess

The original notes correctly identify:

Vitamin D excess.

Vitamin D, particularly its active form:

Calcitriol,

increases gastrointestinal absorption of:

Calcium

and

Phosphate.

Therefore excessive vitamin D activity can cause:

↑ Calcium absorption

and

↑ Phosphate absorption.

16. Vitamin D Toxicity Pattern

Significant vitamin D toxicity typically produces:

Hypercalcaemia

and may produce:

Hyperphosphataemia.

Therefore:

HIGH CALCIUM + HIGH PHOSPHATE

in an appropriate setting can suggest excessive vitamin D activity.

PTH is usually:

Suppressed

because of the hypercalcaemia.

17. Excessive Phosphate Intake

The original notes correctly include:

Over-intake of phosphate.

In people with normal kidney function, the kidneys can usually excrete substantial excess phosphate.

Therefore ordinary dietary phosphate intake does not usually cause major persistent hyperphosphataemia.

The problem becomes more important when the phosphate load is:

Very large

or renal function is:

Impaired.

18. Phosphate-Containing Preparations

Large phosphate loads can occur with certain:

Phosphate-containing medications or bowel preparations.

Excessive phosphate administration can overwhelm renal excretion.

This may produce:

Acute hyperphosphataemia

and secondary:

Hypocalcaemia.

The risk is greater in patients with impaired kidney function.

19. Why Hyperphosphataemia Can Cause Hypocalcaemia

When serum phosphate rises substantially, calcium and phosphate interact.

This can reduce:

Ionised calcium

and promote calcium-phosphate deposition under some circumstances.

Therefore severe acute hyperphosphataemia can be accompanied by:

Hypocalcaemia.

Symptoms may consequently include:

Paraesthesia.

Muscle cramps.

Tetany.

Seizures.

These symptoms are often consequences of the associated low calcium rather than phosphate itself.

20. Tumour Lysis Syndrome

The original notes correctly identify:

Tumour lysis syndrome – TLS

as an extremely important cause of acute hyperphosphataemia.

TLS occurs when large numbers of malignant cells undergo rapid:

Cell lysis.

This may occur spontaneously but is particularly associated with treatment of rapidly proliferating, treatment-sensitive malignancies.

21. Why Phosphate Rises in Tumour Lysis Syndrome

Cells contain substantial amounts of intracellular phosphate.

When tumour cells rupture:

Intracellular phosphate is released into the bloodstream.

Therefore:

MASSIVE CELL LYSIS → PHOSPHATE RELEASE → HYPERPHOSPHATAEMIA.

22. Tumour Lysis Syndrome Pattern

Cell destruction releases:

Potassium.

Phosphate.

Nucleic acids.

Nucleic acids are metabolised to:

Uric acid.

Therefore the classic TLS pattern is:

Potassium ↑

Phosphate ↑

Uric acid ↑

Calcium ↓

with possible:

Acute kidney injury.

23. Why Calcium Falls in TLS

The marked rise in phosphate can contribute to:

Calcium-phosphate precipitation.

Therefore serum calcium falls.

Hence the classic examination pattern:

TUMOUR LYSIS SYNDROME

↓

↑ K⁺

↑ PO₄³⁻

↑ URIC ACID

↓ Ca²⁺

± AKI.

24. Tumour Lysis Syndrome Complications

The metabolic abnormalities can cause:

Cardiac arrhythmias, particularly from hyperkalaemia.

Tetany or seizures from hypocalcaemia.

Acute kidney injury from uric acid and calcium-phosphate-related mechanisms.

TLS is therefore a potentially:

Life-threatening oncological emergency.

25. Other Causes of Cellular Phosphate Release

Tumour lysis syndrome is one example of phosphate release from damaged cells.

Other forms of extensive cellular or tissue breakdown can sometimes cause hyperphosphataemia, including:

Rhabdomyolysis.

Severe haemolysis.

Extensive tissue injury.

The associated clinical context usually makes the cause apparent.

26. Rhabdomyolysis

Skeletal muscle contains large quantities of intracellular phosphate.

When muscle cells undergo necrosis:

Phosphate

and

Potassium

are released.

Therefore rhabdomyolysis can produce:

Hyperphosphataemia + hyperkalaemia.

It may simultaneously cause:

Acute kidney injury, which further reduces phosphate excretion.

27. Pseudohyperphosphataemia

An unexpectedly elevated phosphate concentration should occasionally raise the possibility of:

Laboratory interference or artefact.

Pseudohyperphosphataemia has been described in settings such as:

Paraproteinaemia, including some patients with multiple myeloma, because abnormal proteins may interfere with certain laboratory assays.

Therefore an unexplained phosphate result that does not fit the clinical picture may warrant:

Repeat measurement and laboratory review.

28. Clinical Features

Mild or chronic hyperphosphataemia is often:

Asymptomatic.

Symptoms are more likely when hyperphosphataemia causes or accompanies:

Hypocalcaemia.

Possible features include:

Perioral tingling.

Paraesthesia.

Muscle cramps.

Tetany.

Seizures in severe cases.

29. Chronic Hyperphosphataemia

Persistent hyperphosphataemia, particularly in CKD, can contribute to abnormal:

Calcium-phosphate metabolism.

Over time this can promote:

Vascular calcification.

Soft-tissue calcification.

Secondary hyperparathyroidism.

Renal bone disease.

The chronic consequences are therefore especially important in patients with:

Advanced CKD.

30. Investigation

When hyperphosphataemia is found, useful associated measurements include:

Renal function.

Calcium.

PTH.

ALP.

Vitamin D studies when indicated.

Potassium and uric acid when tumour lysis is suspected.

The clinical context then determines further investigation.

31. Interpreting Calcium With Phosphate

The calcium-phosphate combination can provide useful diagnostic clues.

HIGH PHOSPHATE + LOW CALCIUM + LOW PTH

suggests:

Hypoparathyroidism.

HIGH PHOSPHATE + LOW/NORMAL CALCIUM + HIGH PTH + CKD

suggests:

Secondary hyperparathyroidism due to advanced CKD.

HIGH PHOSPHATE + HIGH CALCIUM + LOW PTH

can occur with:

Vitamin D excess, depending on the clinical context.

HIGH PHOSPHATE + HIGH K + HIGH URATE + LOW CALCIUM

strongly suggests:

Tumour lysis syndrome.

32. Treatment Principles

Treatment depends on the:

Cause, severity, symptoms and renal function.

The central principles are:

Stop excessive phosphate intake or administration.

Treat the underlying cause.

Manage associated hypocalcaemia appropriately.

Reduce phosphate burden when necessary.

33. Hyperphosphataemia in CKD

Management of persistent hyperphosphataemia in CKD may involve:

Dietary phosphate management.

Phosphate-binding medications when indicated.

Adequate dialysis in patients receiving dialysis.

Management of CKD-MBD and secondary hyperparathyroidism.

Treatment is individualised according to serial phosphate, calcium and PTH measurements rather than one isolated result.

34. Phosphate Binders

Phosphate binders act within the gastrointestinal tract.

They bind dietary phosphate and reduce its:

Intestinal absorption.

Examples used in appropriate patients include:

Calcium-containing binders.

Sevelamer.

Lanthanum.

The choice depends on factors including:

Calcium concentration, CKD stage, dialysis status and overall CKD-MBD management.

35. Dialysis

In severe hyperphosphataemia associated with:

Kidney failure

or certain severe acute metabolic disturbances, dialysis can remove phosphate.

However, the need for dialysis is determined by the patient’s overall clinical condition and other indications rather than phosphate concentration alone.

36. Causes of Hyperphosphataemia – Note Form

REDUCED RENAL EXCRETION

Advanced chronic kidney disease/kidney failure.

This is the major cause of persistent hyperphosphataemia.

REDUCED PTH ACTION

Hypoparathyroidism.

↓ PTH

↓

↑ Renal phosphate reabsorption

↓

↑ Phosphate.

INCREASED RENAL PHOSPHATE REABSORPTION

Acromegaly.

GH/IGF-1 excess increases tubular phosphate reabsorption.

INCREASED INTESTINAL ABSORPTION

Vitamin D excess.

Large phosphate intake or phosphate-containing preparations.

CELLULAR RELEASE

Tumour lysis syndrome.

Rhabdomyolysis.

Severe tissue breakdown.

37. Important Clarifications to the Original Notes

The original:

“Renal failure”

is correct and is the most important cause. Hyperphosphataemia is particularly characteristic of:

ADVANCED CKD, because earlier CKD can maintain serum phosphate through increased FGF23 and PTH.

The original:

“Hypoparathyroidism”

is correct.

Remember:

↓ PTH → ↓ PHOSPHATURIA → ↑ PHOSPHATE.

The original:

“Acromegaly”

is correct but is a less common cause. GH/IGF-1 increases:

Renal tubular phosphate reabsorption.

The original:

“Vitamin D excess”

is correct because vitamin D increases:

Intestinal calcium and phosphate absorption.

The original:

“Over-intake of phosphate”

usually requires a substantial phosphate load and is particularly problematic when:

Renal function is impaired.

The original:

“Tumour lysis syndrome”

is extremely important because it causes acute release of:

Potassium + phosphate + nucleic acids from malignant cells.

Key Clinical Pattern

For rapid recall:

HYPERPHOSPHATAEMIA = THINK REDUCED RENAL EXCRETION OR RELEASE/EXCESS PHOSPHATE.

ADVANCED CKD:

↓ GFR → ↓ phosphate excretion → ↑ PO₄³⁻

with:

↑ PTH + ↓/normal Ca²⁺.

HYPOPARATHYROIDISM:

↓ PTH → ↓ phosphaturia

therefore:

↓ Ca²⁺ + ↑ PO₄³⁻ + ↓ PTH.

VITAMIN D EXCESS:

↑ intestinal Ca²⁺ and PO₄³⁻ absorption

therefore often:

↑ Ca²⁺ + ↑ PO₄³⁻ + suppressed PTH.

TUMOUR LYSIS SYNDROME:

↑ K⁺

↑ PO₄³⁻

↑ URIC ACID

↓ Ca²⁺

± AKI.

ACROMEGALY:

↑ GH/IGF-1 → ↑ renal phosphate reabsorption → ↑ PO₄³⁻.

The fastest high-yield distinction is:

LOW PHOSPHATE → think PTH excess, renal phosphate wasting, vitamin D deficiency or intracellular shift.

HIGH PHOSPHATE → think advanced renal failure, low PTH, phosphate load or massive cellular breakdown.

Medicine – Causes of Hypophosphataemia

Hypophosphataemia means an abnormally low concentration of phosphate in the blood. In adults, it is generally defined as:

Serum phosphate <0.8 mmol/L (≈2.5 mg/dL).

Severe hypophosphataemia is commonly considered:

<0.32 mmol/L (≈1.0 mg/dL).

Phosphate is essential for ATP production, cellular energy metabolism, bone mineralisation, cell membranes, 2,3-BPG production and intracellular signalling. Severe phosphate depletion can therefore cause major neuromuscular, respiratory, cardiac and haematological complications.

1. Major Mechanisms

The causes of hypophosphataemia are easiest to understand through three mechanisms:

Redistribution of phosphate from blood into cells.

Reduced intestinal phosphate absorption.

Increased renal phosphate loss.

The original causes fit well into these categories.

2. Intracellular Redistribution

Several important causes do not initially represent loss of phosphate from the body.

Instead:

Phosphate moves from extracellular fluid → into cells.

This can rapidly reduce the serum phosphate concentration.

Important examples include:

Intravenous glucose.

Refeeding syndrome.

Insulin treatment of DKA.

Respiratory alkalosis.

3. Intravenous Glucose

The original notes correctly identify:

Intravenous glucose.

Administration of glucose stimulates:

Insulin secretion.

Insulin promotes movement of:

Glucose + phosphate + potassium

into cells.

Therefore:

IV GLUCOSE → ↑ INSULIN → PHOSPHATE MOVES INTO CELLS → ↓ SERUM PHOSPHATE.

This effect becomes particularly important when the patient already has depleted total-body phosphate stores.

4. Insulin and Phosphate

Inside cells, glucose undergoes phosphorylation as part of:

Glycolysis and other metabolic pathways.

This increases intracellular utilisation of phosphate.

Therefore insulin-driven carbohydrate metabolism can produce a substantial fall in serum phosphate.

A similar mechanism explains hypophosphataemia during:

Refeeding syndrome

and treatment of:

DKA.

5. Refeeding Syndrome

The original notes correctly identify:

Refeeding syndrome

as one of the most important causes of severe hypophosphataemia.

It occurs when nutrition, particularly carbohydrate, is rapidly reintroduced after a period of:

Starvation or severe malnutrition.

6. Mechanism of Refeeding Syndrome

During prolonged starvation:

Insulin levels fall.

The body shifts toward:

Fat and protein metabolism.

Total-body stores of:

Phosphate, potassium and magnesium

become depleted, even though their serum concentrations may initially appear relatively normal.

When carbohydrate feeding is restarted:

↑ Glucose

↓

↑ Insulin

↓

Glucose enters cells

• ●

Phosphate enters cells

• ●

K⁺ enters cells

• ●

Mg²⁺ shifts/requirements increase

↓

Rapid hypophosphataemia

with possible:

Hypokalaemia and hypomagnesaemia.

7. Why Refeeding Hypophosphataemia Is Dangerous

Phosphate is required for:

ATP production.

When phosphate falls severely, ATP-dependent tissues can fail.

This can cause:

Muscle weakness.

Respiratory muscle failure.

Cardiac dysfunction.

Arrhythmias.

Neurological deterioration.

Therefore severe refeeding syndrome can be:

Life-threatening.

8. Patients at Risk of Refeeding Syndrome

Important risk settings include prolonged:

Starvation.

Severe malnutrition.

Eating disorders.

Chronic excessive alcohol use.

Cancer-associated malnutrition.

Prolonged inadequate nutritional intake.

Nutrition must therefore be introduced carefully in high-risk patients, with monitoring and replacement of:

Phosphate, potassium, magnesium and thiamine, as appropriate.

9. Alcohol-Related Hypophosphataemia

The original notes state:

Alcohol withdrawal.

This association is correct, but the mechanism is usually multifactorial.

People with chronic excessive alcohol use may have:

Poor dietary phosphate intake.

Malnutrition.

Vitamin D deficiency.

Renal phosphate wasting.

Vomiting or diarrhoea.

Hypomagnesaemia.

10. Alcohol Withdrawal

During acute alcohol withdrawal, patients may develop:

Hyperventilation.

This can produce:

Respiratory alkalosis.

Respiratory alkalosis itself can cause a rapid intracellular phosphate shift.

Therefore:

ALCOHOL WITHDRAWAL → HYPERVENTILATION → RESPIRATORY ALKALOSIS → PHOSPHATE SHIFTS INTO CELLS → HYPOPHOSPHATAEMIA.

Poor nutritional status can make the fall substantially worse.

11. Respiratory Alkalosis – Important Additional Cause

An important cause not explicitly included in the original list is:

Respiratory alkalosis.

When PaCO₂ falls:

Intracellular pH rises.

This stimulates:

Phosphofructokinase

and increases intracellular glycolysis.

Phosphate is consumed in phosphorylated metabolic intermediates and moves into cells.

Therefore:

ACUTE RESPIRATORY ALKALOSIS → INTRACELLULAR PHOSPHATE SHIFT → HYPOPHOSPHATAEMIA.

Severe hyperventilation can cause a substantial fall.

12. DKA and Hypophosphataemia

The original notes correctly include:

Recovery/treatment phase of diabetic ketoacidosis – DKA.

Patients with DKA commonly have:

Total-body phosphate depletion.

However, the serum phosphate at presentation may initially be:

Normal or even elevated.

This can be misleading.

13. Why Total-Body Phosphate Is Low in DKA

Severe hyperglycaemia causes:

Osmotic diuresis.

This leads to urinary loss of:

Water.

Sodium.

Potassium.

Phosphate.

Therefore total-body phosphate stores become depleted.

At the same time, insulin deficiency and acidosis may shift phosphate out of cells, partially maintaining the initial serum concentration.

14. Why Phosphate Falls During DKA Treatment

Treatment includes:

Insulin + fluids.

Insulin causes:

Phosphate to move back into cells.

Therefore:

DKA → TOTAL-BODY PHOSPHATE DEPLETION

followed by:

INSULIN TREATMENT → INTRACELLULAR PHOSPHATE SHIFT

↓

SERUM PHOSPHATE FALLS.

Thus hypophosphataemia commonly becomes more apparent during treatment rather than at initial presentation.

15. Phosphate Replacement in DKA

Routine phosphate replacement is not required for every patient with DKA.

Replacement is generally considered when hypophosphataemia is:

Severe

or associated with important clinical consequences such as:

Respiratory weakness.

Cardiac dysfunction.

Marked muscle weakness.

Management depends on the patient’s phosphate level and overall clinical condition.

16. Primary Hyperparathyroidism

The original notes correctly identify:

Primary hyperparathyroidism.

In this disorder:

PTH is elevated or inappropriately normal in the presence of hypercalcaemia.

PTH has an important effect on the:

Proximal renal tubule.

17. PTH Causes Phosphate Wasting

PTH reduces proximal tubular phosphate reabsorption.

Therefore:

↑ PTH

↓

↓ Renal phosphate reabsorption

↓

↑ Urinary phosphate excretion

↓

Hypophosphataemia.

This is called:

Phosphaturia.

18. Primary Hyperparathyroidism Pattern

The characteristic pattern is:

Calcium: ↑

Phosphate: ↓ or low-normal

PTH: ↑ or inappropriately normal

ALP: normal or ↑

Therefore:

HIGH CALCIUM + LOW PHOSPHATE → THINK PRIMARY HYPERPARATHYROIDISM, especially when PTH is not appropriately suppressed.

19. Renal Tubular Disease

The original notes correctly include:

Renal tubular disease.

The:

Proximal renal tubule

is responsible for reabsorbing most filtered phosphate.

Therefore proximal tubular dysfunction can cause:

Renal phosphate wasting.

20. Fanconi Syndrome

The classic example is:

Fanconi syndrome.

This is generalised proximal tubular dysfunction causing urinary loss of substances that should normally be reabsorbed.

These include:

Phosphate.

Glucose.

Amino acids.

Bicarbonate.

Uric acid.

Therefore:

FANCONI SYNDROME → PHOSPHATURIA → HYPOPHOSPHATAEMIA → OSTEOMALACIA/RICKETS.

21. Proximal Renal Tubular Acidosis

Fanconi syndrome may be associated with:

Type 2 – proximal renal tubular acidosis.

Loss of bicarbonate produces:

Normal-anion-gap metabolic acidosis.

If phosphate is also lost:

Hypophosphataemia

and eventually:

Osteomalacia or rickets

may develop.

22. Vitamin D Deficiency

The original notes correctly include:

Vitamin D deficiency.

Vitamin D normally increases intestinal absorption of:

Calcium and phosphate.

Therefore vitamin D deficiency reduces intestinal phosphate absorption.

However, there is another important mechanism.

23. Vitamin D Deficiency and Secondary Hyperparathyroidism

Vitamin D deficiency reduces:

Calcium absorption.

↓

Serum calcium tends to fall.

↓

PTH rises.

↓

PTH increases:

Renal phosphate excretion.

↓

Serum phosphate falls.

Therefore phosphate becomes low because of both:

Reduced intestinal absorption

and

Secondary hyperparathyroidism causing phosphaturia.

24. Vitamin D Deficiency Pattern

In significant vitamin D deficiency causing osteomalacia:

Calcium: ↓ or low-normal

Phosphate: ↓

ALP: ↑

PTH: ↑

25(OH) vitamin D: ↓

Therefore:

LOW PHOSPHATE + HIGH ALP + HIGH PTH + LOW VITAMIN D → THINK VITAMIN D DEFICIENCY OSTEOMALACIA.

25. Reduced Intestinal Absorption

Hypophosphataemia can also result from reduced phosphate absorption due to:

Malnutrition.

Malabsorption.

Chronic diarrhoea.

Vitamin D deficiency.

Certain phosphate-binding medications can also reduce intestinal absorption.

Usually severe hypophosphataemia requires either substantial depletion or another contributing mechanism.

26. Renal Phosphate Wasting

Renal phosphate wasting is an important broad category.

Causes include:

Primary hyperparathyroidism.

Fanconi syndrome/proximal tubular disease.

FGF23-mediated disorders.

Certain medications.

The defining concept is:

The kidneys continue losing phosphate despite a low serum phosphate concentration.

27. FGF23 and Phosphate

FGF23 – fibroblast growth factor 23 is an important phosphate-regulating hormone.

It decreases renal phosphate reabsorption.

Therefore excessive FGF23 activity causes:

Phosphaturia

↓

Hypophosphataemia.

It also alters vitamin D metabolism.

28. X-Linked Hypophosphataemia

An important inherited cause is:

X-linked hypophosphataemia.

Excessive FGF23 activity causes persistent:

Renal phosphate wasting.

Children may develop:

Rickets

while adults can develop:

Osteomalacia and skeletal complications.

29. Tumour-Induced Osteomalacia

Certain usually small mesenchymal tumours can produce excessive:

FGF23.

This causes:

Renal phosphate wasting

↓

Persistent hypophosphataemia

↓

Defective bone mineralisation

↓

Osteomalacia.

Therefore unexplained persistent hypophosphataemia with renal phosphate wasting should raise consideration of an:

FGF23-mediated disorder.

30. Clinical Features of Hypophosphataemia

Mild hypophosphataemia may be:

Asymptomatic.

Symptoms become increasingly important when phosphate falls severely or rapidly.

Because phosphate is essential for ATP generation, severe deficiency affects tissues with high energy requirements.

31. Muscle Weakness

A common manifestation is:

Generalised muscle weakness.

Severe deficiency can particularly affect:

Respiratory muscles.

This may contribute to:

Respiratory failure

or difficulty weaning a critically ill patient from mechanical ventilation.

32. Neurological Features

Severe hypophosphataemia can cause:

Irritability.

Confusion.

Paraesthesia.

Seizures.

Encephalopathy.

Coma in extreme cases.

33. Cardiac Effects

Severe phosphate depletion can impair myocardial energy metabolism.

Possible consequences include:

Reduced myocardial contractility.

Heart failure.

Arrhythmias.

These complications are particularly important in critically ill patients.

34. Haematological Effects

Phosphate is required for normal cellular metabolism.

Severe deficiency can contribute to:

Haemolysis.

Impaired leukocyte function.

Platelet dysfunction.

It can also reduce red-cell:

2,3-BPG.

This increases haemoglobin’s affinity for oxygen and can impair:

Oxygen delivery to tissues.

35. Chronic Hypophosphataemia and Bone

Persistent phosphate deficiency interferes with formation of:

Hydroxyapatite.

Therefore chronic hypophosphataemia can cause:

Osteomalacia in adults

and

Rickets in children.

This may present with:

Bone pain.

Fractures.

Skeletal deformity.

Proximal muscle weakness.

36. Investigation

When hypophosphataemia is identified, the central question is:

Is phosphate moving into cells, being inadequately absorbed, or being lost through the kidneys?

Useful investigations depend on the clinical context and may include:

Serum calcium.

Magnesium.

Renal function.

PTH.

25-hydroxyvitamin D.

Acid–base status.

Glucose.

Assessment of urinary phosphate excretion may be useful when:

Renal phosphate wasting is suspected.

37. Urinary Phosphate

When serum phosphate is low, healthy kidneys should respond by:

Strongly conserving phosphate.

Therefore:

Low urinary phosphate in hypophosphataemia

suggests an appropriate renal response and points toward:

Intracellular redistribution or reduced intestinal availability.

In contrast:

Inappropriately high urinary phosphate despite hypophosphataemia

suggests:

Renal phosphate wasting.

Think particularly about:

Hyperparathyroidism.

Fanconi syndrome.

FGF23-mediated disease.

38. Treatment Principles

Treatment depends on:

Severity.

Symptoms.

Underlying mechanism.

Renal function.

Associated electrolyte abnormalities.

The underlying cause must always be addressed.

39. Mild to Moderate Hypophosphataemia

When clinically appropriate, mild or moderate deficiency may be treated with:

Oral phosphate

and correction of the underlying disorder.

Associated deficiencies such as:

Vitamin D deficiency

should also be treated where appropriate.

40. Severe Hypophosphataemia

Severe or symptomatic hypophosphataemia may require:

Intravenous phosphate replacement

with close monitoring.

IV phosphate requires caution because excessive replacement can cause complications including:

Hypocalcaemia.

Hyperphosphataemia.

Calcium-phosphate precipitation.

Arrhythmias.

The risk is greater when renal function is impaired.

41. Causes – Note Form

INTRACELLULAR SHIFT:

Intravenous glucose.

Insulin therapy.

Refeeding syndrome.

Treatment/recovery phase of DKA.

Respiratory alkalosis.

Alcohol withdrawal, particularly with hyperventilation.

REDUCED INTESTINAL AVAILABILITY:

Vitamin D deficiency.

Malnutrition.

Malabsorption.

Chronic diarrhoea.

Phosphate-binding medications in appropriate circumstances.

INCREASED RENAL PHOSPHATE LOSS:

Primary hyperparathyroidism.

Proximal tubular disease.

Fanconi syndrome.

FGF23-mediated disorders.

X-linked hypophosphataemia.

Tumour-induced osteomalacia.

42. Important Clarifications to the Original Notes

The original:

“Intravenous glucose”

is correct, but the key mechanism is:

GLUCOSE → INSULIN → PHOSPHATE SHIFTS INTO CELLS.

The original:

“Refeeding syndrome”

is particularly important.

The hallmark electrolyte abnormality is:

HYPOPHOSPHATAEMIA, often accompanied by hypokalaemia and hypomagnesaemia.

The original:

“Alcohol withdrawal”

is correct but multifactorial. An important acute mechanism is:

HYPERVENTILATION → RESPIRATORY ALKALOSIS → INTRACELLULAR PHOSPHATE SHIFT.

The original:

“Recovery phase of DKA”

is better understood as:

DKA causes total-body phosphate depletion through osmotic diuresis, and insulin treatment then shifts phosphate into cells, revealing or worsening hypophosphataemia.

The original:

“Primary hyperparathyroidism”

causes:

RENAL PHOSPHATE WASTING.

Therefore remember:

↑ PTH → ↓ renal phosphate reabsorption → ↓ serum phosphate.

The original:

“Renal tubular disease”

particularly means:

PROXIMAL TUBULAR DYSFUNCTION, especially Fanconi syndrome.

The original:

“Vitamin D deficiency”

causes both:

Reduced intestinal phosphate absorption

and

Secondary hyperparathyroidism → renal phosphate wasting.

Key Clinical Pattern

For rapid recall, think of hypophosphataemia as:

SHIFT – LOW ABSORPTION – RENAL LOSS.

SHIFT INTO CELLS:

GLUCOSE/INSULIN + REFEEDING + DKA TREATMENT + RESPIRATORY ALKALOSIS.

RENAL LOSS:

HYPERPARATHYROIDISM + FANCONI/PROXIMAL TUBULAR DISEASE + FGF23 EXCESS.

REDUCED AVAILABILITY:

VITAMIN D DEFICIENCY + MALNUTRITION + MALABSORPTION.

The particularly high-yield associations are:

MALNOURISHED PATIENT + FEEDING STARTED + RAPID ↓ PO₄³⁻ → REFEEDING SYNDROME.

DKA + INSULIN TREATMENT + ↓ PO₄³⁻ → INTRACELLULAR PHOSPHATE SHIFT ON A BACKGROUND OF TOTAL-BODY DEPLETION.

↑ Ca²⁺ + ↑ PTH + ↓ PO₄³⁻ → PRIMARY HYPERPARATHYROIDISM.

↓ PO₄³⁻ + GLYCOSURIA WITHOUT HYPERGLYCAEMIA + BICARBONATE LOSS → FANCONI SYNDROME.

↓ PO₄³⁻ + ↑ ALP + ↑ PTH + ↓ 25(OH)D → VITAMIN D DEFICIENCY OSTEOMALACIA.

And the major danger of profound hypophosphataemia is:

ATP DEPLETION → SEVERE MUSCLE WEAKNESS, RESPIRATORY FAILURE, CARDIAC DYSFUNCTION AND NEUROLOGICAL DISTURBANCE.

Medicine – Osteomalacia and Rickets

Osteomalacia and rickets are metabolic bone disorders caused by defective mineralisation of newly formed osteoid. The fundamental abnormality is failure to adequately deposit calcium and phosphate crystals into the organic bone matrix.

The terminology depends mainly on whether the growth plates are still open:

Osteomalacia → defective mineralisation in adults after epiphyseal closure.

Rickets → defective mineralisation in children before epiphyseal closure, involving both bone and the growth plates.

The most important cause worldwide is vitamin D deficiency, although disorders of calcium, phosphate and renal tubular handling can produce the same fundamental defect.

1. Normal Bone Mineralisation

Osteoblasts first produce an organic bone matrix called: