Ophthalmology – Acquired Nystagmus

Basics

Description

Acquired nystagmus is a repetitive, involuntary oscillation of the eyes that develops after infancy or after a period of previously stable ocular motor function.

It may be:

• Constant
• Intermittent
• Cyclic
• Monocular
• Binocular
• Asymmetric or dissociated

Nystagmus develops when the eyes cannot maintain a stable position of gaze and drift away from the desired target.

The oscillation may be:

• Pendular – movements have approximately equal velocity in both directions
• Jerk – slow drift in one direction followed by a corrective fast phase

Acquired nystagmus often causes:

• Oscillopsia
• Reduced visual acuity
• Imbalance
• Vertigo
• Ataxia

Epidemiology

Acquired nystagmus is uncommon.

Population prevalence estimates for all forms of nystagmus are approximately:

240 per 100,000

The prevalence of individual acquired forms depends strongly on the underlying neurologic, vestibular, toxic, or structural disorder.

Risk Factors

There are no single universal risk factors because acquired nystagmus has many causes.

Potential predisposing conditions include:

• Cerebellar disease
• Brainstem disease
• Multiple sclerosis
• Stroke
• Vestibular disorders
• Medication toxicity
• Alcohol or sedative exposure
• Nutritional deficiencies
• Craniocervical junction abnormalities
• Tumors
• Severe visual pathway disease

Genetics

Most acquired nystagmus is not inherited.

However, inherited neurologic conditions may produce nystagmus, including:

• Episodic ataxias
• Mitochondrial disease
• Leukodystrophies
• Congenital cerebellar disorders

Pathophysiology

Stable vision requires the retinal image to remain relatively stationary.

Three major systems stabilize gaze:

• Vestibulo-ocular reflex
• Visual fixation system
• Neural integrator for eccentric gaze holding

Failure of any of these systems may cause nystagmus.

Vestibulo-Ocular Reflex

The vestibulo-ocular reflex stabilizes vision during head movement.

Abnormal asymmetry of vestibular tone may cause:

• Slow drift of the eyes
• Corrective fast phases

This produces vestibular jerk nystagmus.

Visual Fixation

Visual fixation stabilizes the target through:

• Corrective eye movements when retinal image drift occurs
• Suppression of unwanted eye movements

Severe visual pathway disease may impair these mechanisms.

Neural Integrator

The neural integrator converts brief eye-movement commands into sustained tonic signals that keep the eyes in eccentric gaze.

Important structures include:

Horizontal gaze holding

• Medial vestibular nucleus
• Nucleus prepositus hypoglossi
• Cerebellar flocculus and related pathways

Vertical and torsional gaze holding

• Interstitial nucleus of Cajal

Failure of the neural integrator causes the eyes to drift back toward primary position, followed by corrective saccades.

This produces:

Gaze-evoked nystagmus

Pulse-Step Mechanism

A saccade requires:

• A pulse of neural activity to rapidly move the eye
• A step of tonic activity to hold the new position

If the step is insufficient relative to the pulse, the eyes drift back after the saccade.

This mismatch may produce:

• Glissades
• Gaze-evoked nystagmus

Classification

Important forms of acquired nystagmus include:

• Peripheral vestibular nystagmus
• Downbeat nystagmus
• Upbeat nystagmus
• Torsional nystagmus
• Periodic alternating nystagmus
• See-saw nystagmus
• Acquired pendular nystagmus
• Gaze-evoked nystagmus
• Oculopalatal tremor

Symptoms

The hallmark symptom of acquired nystagmus is:

Oscillopsia

This is the false perception that stationary objects are moving.

Patients may describe:

• Shaking vision
• Jumping images
• Blurred vision during head movement
• Difficulty reading
• Poor balance
• Vertigo
• Nausea

Oscillopsia is much more common in acquired than congenital nystagmus because patients have not adapted neurologically to the ocular oscillation.

Peripheral Vestibular Nystagmus

Peripheral vestibular disease produces a characteristic jerk nystagmus.

Typical features include:

• Horizontal-torsional direction
• Unidirectional fast phase
• Worsening when looking toward the fast phase
• Suppression with visual fixation
• Increased intensity in darkness or with Frenzel goggles
• Association with vertigo and nausea

Alexander’s Law

Peripheral vestibular nystagmus usually follows Alexander’s law:

The nystagmus becomes more intense when the patient looks in the direction of the fast phase.

Benign Paroxysmal Positional Vertigo

BPPV is a common peripheral vestibular cause.

It most commonly involves the:

Posterior semicircular canal

Typical findings include:

• Brief positional vertigo
• Characteristic torsional-upbeating nystagmus during positional testing
• Latency before onset
• Fatigability
• Short duration

Dix-Hallpike Test

The Dix-Hallpike maneuver is used to diagnose posterior canal BPPV.

A typical response includes:

• Vertigo
• Torsional-upbeating nystagmus
• Brief latency
• Fatigability

Treatment of BPPV

The main treatment is:

Canalith repositioning

Common maneuvers include:

• Epley maneuver
• Semont maneuver

Routine long-term use of vestibular suppressants is discouraged because they may:

• Delay central compensation
• Cause sedation
• Increase fall risk

Short-term antiemetic or vestibular suppressant use may be appropriate for severe symptoms.

Downbeat Nystagmus

Downbeat nystagmus is a central vestibular nystagmus in which the fast phase is downward.

It often becomes more prominent in:

• Lateral gaze
• Downgaze
• Convergence

It strongly suggests disease involving the:

• Cerebellar flocculus
• Vestibulocerebellum
• Craniocervical junction

Causes of Downbeat Nystagmus

Important causes include:

• Chiari I malformation
• Cerebellar degeneration
• Multiple sclerosis
• Stroke
• Brainstem or cerebellar tumor
• Craniocervical junction disease
• Hydrocephalus
• Trauma
• Toxicity from medications

Medication causes include:

• Anticonvulsants
• Lithium
• Sedative drugs
• Some antiarrhythmics

Metabolic and deficiency states include:

• Vitamin B12 deficiency
• Thiamine deficiency
• Magnesium deficiency

Episodic Ataxia Type 2

Downbeat nystagmus may occur with:

Episodic ataxia type 2

This is associated with pathogenic variants in:

CACNA1A

Patients may have:

• Episodic vertigo
• Ataxia
• Interictal downbeat nystagmus

Acetazolamide may reduce attacks in selected patients.

Treatment of Downbeat Nystagmus

Treatment should first address the cause.

Symptomatic medications sometimes used include:

• 4-aminopyridine / dalfampridine
• Baclofen
• Clonazepam in selected cases

4-aminopyridine is often one of the more effective pharmacologic options for persistent downbeat nystagmus.

Medication choice requires neurologic supervision because of potential adverse effects, particularly seizure risk with aminopyridines.

Upbeat Nystagmus

Upbeat nystagmus has an upward fast phase.

It usually reflects central pathology involving:

• Medulla
• Pons
• Midbrain
• Cerebellum

Causes of Upbeat Nystagmus

Important causes include:

• Brainstem stroke
• Multiple sclerosis
• Wernicke encephalopathy
• Cerebellar degeneration
• Tumors
• Behçet disease
• Drug toxicity

Treatment of Upbeat Nystagmus

Treatment focuses on the underlying disorder.

Symptomatic therapy may occasionally include:

• Baclofen
• Aminopyridines

Evidence is less robust than for downbeat nystagmus.

Torsional Nystagmus

Pure torsional nystagmus is uncommon.

It may occur with:

• Brainstem lesions
• Vestibular pathway lesions
• Ocular tilt reaction
• Skew deviation

It should generally prompt neurologic evaluation.

Periodic Alternating Nystagmus

Periodic alternating nystagmus (PAN) is a horizontal jerk nystagmus that periodically reverses direction.

The cycle typically lasts approximately:

1.5–2 minutes

before changing direction.

Causes of PAN

Associated conditions include:

• Cerebellar disease
• Multiple sclerosis
• Craniocervical junction disorders
• Visual pathway disease
• Congenital ocular motor disorders

Treatment of PAN

Baclofen is the classic treatment.

It may reduce:

• Nystagmus amplitude
• Directional reversals
• Oscillopsia

See-Saw Nystagmus

See-saw nystagmus is a disconjugate vertical-torsional oscillation.

Classically:

• One eye elevates and intorts
• The other eye depresses and extorts

Then the movements reverse.

Causes of See-Saw Nystagmus

Strongly associated with:

• Parasellar lesions
• Optic chiasm lesions
• Midbrain compression
• Congenital chiasmal abnormalities

It may be seen with:

• Pituitary region tumors
• Craniopharyngioma
• Severe chiasmal visual loss

Acquired Pendular Nystagmus

Acquired pendular nystagmus is strongly associated with:

Multiple sclerosis

It may be:

• Horizontal
• Vertical
• Torsional
• Elliptical
• Circular
• Dissociated between the two eyes

Other Causes of Acquired Pendular Nystagmus

Include:

• Brainstem stroke
• Cerebellar stroke
• Tumors
• Demyelinating disease
• Mitochondrial disorders
• Leukodystrophies
• Toxic exposure

Treatment of Acquired Pendular Nystagmus

Most commonly used symptomatic treatments include:

• Gabapentin
• Memantine

These can reduce:

• Oscillation amplitude
• Oscillopsia

Clonazepam may help some patients but often causes sedation.

Gaze-Evoked Nystagmus

Gaze-evoked nystagmus appears when the eyes are held eccentrically.

The slow phase is directed toward:

Primary position

It results from impaired neural integration.

Causes of Gaze-Evoked Nystagmus

Common causes include:

• Sedative-hypnotic medications
• Alcohol
• Anticonvulsants
• Cerebellar disease
• Brainstem disease

A small amount of endpoint nystagmus at extreme gaze may be physiologic, but persistent or asymmetric gaze-evoked nystagmus is abnormal.

Oculopalatal Tremor

Formerly called oculopalatal myoclonus, this is an acquired pendular oscillation associated with lesions in the Guillain-Mollaret triangle.

This circuit includes:

• Dentate nucleus
• Red nucleus
• Central tegmental tract
• Inferior olivary nucleus

Clinical Features of Oculopalatal Tremor

Ocular movement is often:

• Vertical
• Torsional
• Pendular

Frequency is approximately:

1–3 Hz

It may be accompanied by rhythmic movement of:

• Palate
• Pharynx
• Larynx
• Facial muscles

MRI in Oculopalatal Tremor

MRI may show:

Hypertrophic degeneration of the inferior olivary nucleus

This often develops months after the causative brainstem or cerebellar lesion.

Causes of Oculopalatal Tremor

Common causes include:

• Brainstem hemorrhage
• Brainstem infarction
• Cerebellar hemorrhage
• Tumor
• Demyelinating disease

Treatment of Oculopalatal Tremor

Symptomatic options include:

• Gabapentin
• Memantine

Other agents are less consistently effective.

Diagnosis

History

Ask about:

• Onset
• Duration
• Constant versus intermittent symptoms
• Oscillopsia
• Vertigo
• Ataxia
• Hearing symptoms
• Diplopia
• Headache
• Recent stroke-like symptoms
• Medication use
• Alcohol exposure
• Anticonvulsants
• Lithium
• Sedatives
• Toxic exposures

Neurologic Red Flags

Acquired nystagmus accompanied by:

• New ataxia
• Weakness
• Dysarthria
• Sensory loss
• Severe headache
• Cranial nerve palsy
• Altered consciousness

requires urgent evaluation for a central neurologic cause.

Examination

Characterize:

• Direction
• Plane
• Waveform
• Conjugacy
• Frequency
• Amplitude
• Effect of gaze
• Effect of fixation
• Effect of convergence
• Effect of head position

Fast Phase Naming

Jerk nystagmus is named according to the:

Direction of the fast phase

For example:

• Downbeat nystagmus → fast phase downward
• Right-beating nystagmus → fast phase rightward

Fixation Suppression

Peripheral vestibular nystagmus is generally:

Reduced by fixation

Central nystagmus is less likely to suppress with fixation and may persist or worsen.

Ophthalmoscopy

Direct ophthalmoscopy can sometimes make the movement easier to appreciate because the optic disc and retinal vessels provide a stable reference.

Video-Oculography

Eye movement recordings can objectively measure:

• Frequency
• Amplitude
• Slow-phase velocity
• Waveform

These may help distinguish nystagmus from saccadic oscillations.

Laboratory Testing

Routine laboratory testing is usually not helpful unless a specific cause is suspected.

Selected tests may include:

• Blood alcohol level
• Toxicology screen
• Vitamin B12
• Thiamine-related evaluation
• Magnesium
• Drug levels

depending on history.

Neuroimaging

MRI of the brain, particularly the posterior fossa and craniocervical junction, is often the imaging study of choice for unexplained acquired nystagmus.

Useful sequences include:

• T1
• T2
• FLAIR
• Diffusion-weighted imaging
• Post-contrast imaging when indicated

When MRI Is Particularly Important

MRI is strongly indicated for:

• Downbeat nystagmus
• Upbeat nystagmus
• Pure torsional nystagmus
• See-saw nystagmus
• New acquired pendular nystagmus
• Associated neurologic signs
• Suspected brainstem/cerebellar disease

Differential Diagnosis

Important mimics include:

• Saccadic intrusions
• Ocular flutter
• Opsoclonus
• Square-wave jerks
• Macrosaccadic oscillations
• Superior oblique myokymia
• Ocular neuromyotonia

Saccadic Intrusions

Unlike nystagmus, saccadic intrusions consist primarily of:

Rapid saccades rather than a slow drift followed by a fast correction

Examples include:

• Square-wave jerks
• Ocular flutter
• Opsoclonus
• Macrosaccadic oscillations

Ocular Flutter

Characterized by:

• Back-to-back horizontal saccades
• No intersaccadic interval

It may be associated with:

• Paraneoplastic disease
• Encephalitis
• Toxic-metabolic states

Opsoclonus

Opsoclonus consists of:

• Chaotic
• Multidirectional
• Back-to-back saccades

It may occur with:

• Paraneoplastic syndromes
• Neuroblastoma in children
• Autoimmune encephalitis
• Postinfectious states

Superior Oblique Myokymia

Produces:

• Brief
• Monocular
• Vertical-torsional oscillopsia

Patients often describe:

• Shimmering
• Trembling vision
• Brief episodes triggered by gaze

It is usually due to abnormal trochlear nerve excitability.

Ocular Neuromyotonia

Characterized by episodic tonic deviation of one eye, often triggered by prolonged eccentric gaze.

It is most often seen after:

• Parasellar radiation

It may affect:

• Oculomotor nerve
• Trochlear nerve
• Abducens nerve

Treatment Principles

Treatment has two goals:

1. Identify and treat the underlying cause
2. Reduce disabling oscillopsia or visual blur

Cause-Specific Treatment

Examples include:

• BPPV → canalith repositioning
• Chiari malformation → neurosurgical evaluation when symptomatic
• Nutritional deficiency → replacement therapy
• Medication toxicity → stop or reduce offending drug when appropriate
• Multiple sclerosis → neurologic treatment
• Stroke → vascular management and rehabilitation
• Wernicke encephalopathy → urgent thiamine

Pharmacologic Treatment

Treatment depends strongly on the nystagmus type.

Commonly used agents include:

Downbeat nystagmus

• 4-aminopyridine / dalfampridine
• Baclofen
• Clonazepam in selected patients

Periodic alternating nystagmus

• Baclofen

Acquired pendular nystagmus

• Gabapentin
• Memantine

Oculopalatal tremor

• Gabapentin
• Memantine

Medication choice should be individualized because adverse effects such as:

• Sedation
• Dizziness
• Ataxia
• Seizures
• Cognitive impairment

may limit treatment.

Treatments Generally Not Recommended

Older reports described symptomatic benefit from:

• Alcohol
• Cannabis
• High-dose anticholinergic drugs

These are not standard treatments because of limited evidence and substantial adverse effects.

Optical Treatment

Selected patients may benefit from:

• Prisms
• Contact lenses
• Refractive optimization

Prisms may shift gaze toward a position where nystagmus is reduced.

Null Point

Some patients have a gaze position in which nystagmus intensity is minimal.

This is called the:

Null point

Patients may adopt an abnormal head posture to maintain the eyes in that position.

Surgery

Extraocular muscle surgery may be considered when:

• There is a stable null point
• A disabling abnormal head posture is present
• Medical treatment fails

Procedures may shift the eyes toward the null position.

Surgery is less commonly used for acquired than congenital nystagmus.

Botulinum Toxin

Botulinum toxin injections into extraocular muscles have occasionally been used for severe acquired nystagmus.

Limitations include:

• Ptosis
• Diplopia
• Induced strabismus
• Variable duration
• Incomplete benefit

Therefore, it is not routinely used.

Retinal Image Stabilization

Special optical systems have historically been designed to reduce retinal image movement.

These are rarely used in routine practice because of:

• Complexity
• Limited practicality
• Visual field restriction

Follow-Up

Follow-up depends entirely on the cause.

Patients with new acquired nystagmus generally require reassessment of:

• Visual acuity
• Oscillopsia
• Eye movement characteristics
• Neurologic findings
• Treatment response

Prognosis

Prognosis varies.

Peripheral vestibular causes

Often improve or resolve, particularly:

• BPPV
• Acute vestibular neuritis

Central causes

May persist chronically, especially when related to:

• Multiple sclerosis
• Structural brainstem lesions
• Cerebellar degeneration
• Oculopalatal tremor

Patient Education

Patients should understand that acquired nystagmus is usually a sign of an underlying ocular motor, vestibular, neurologic, or toxic disorder, rather than a diagnosis by itself.

Urgent evaluation is warranted when nystagmus is associated with:

• New severe headache
• Weakness
• Dysarthria
• Severe ataxia
• Diplopia
• Loss of consciousness
• Other acute neurologic symptoms

Ophthalmology Pearls

• Acquired nystagmus usually causes oscillopsia; congenital nystagmus often does not.
• Nystagmus contains a slow drift phase; saccadic intrusions consist primarily of rapid saccades.
• Downbeat nystagmus strongly suggests cerebellar or craniocervical junction disease, especially Chiari malformation.
• Upbeat nystagmus suggests central brainstem or cerebellar pathology.
• Peripheral vestibular nystagmus is usually unidirectional, suppressed by fixation, and follows Alexander’s law.
• Posterior canal BPPV typically causes torsional-upbeating positional nystagmus and is treated with an Epley-type canalith repositioning maneuver.
• Periodic alternating nystagmus reverses direction every 1–2 minutes and often responds to baclofen.
• Acquired pendular nystagmus is classically associated with multiple sclerosis and may respond to gabapentin or memantine.
• See-saw nystagmus should raise concern for parasellar or chiasmal disease.
• Oculopalatal tremor is associated with lesions in the Guillain-Mollaret triangle and may show hypertrophic inferior olivary degeneration on MRI.
• Persistent new acquired nystagmus generally warrants careful neurologic examination and, when unexplained, MRI of the brain/posterior fossa.