Medicine – Third Nerve Palsy

Third nerve palsy is dysfunction of the oculomotor nerve, cranial nerve III, which supplies most of the extraocular muscles, the levator palpebrae superioris, and parasympathetic fibres responsible for pupillary constriction.

A useful memory rule is:

LR6 SO4, all the rest 3

meaning:

Lateral rectus → CN VI

Superior oblique → CN IV

Most other extraocular muscles → CN III

1. Muscles Supplied by the Third Cranial Nerve

The oculomotor nerve supplies most muscles responsible for eye movement.

These include:

Medial rectus.

Superior rectus.

Inferior rectus.

Inferior oblique.

It also supplies:

Levator palpebrae superioris, which raises the upper eyelid.

The two major extraocular muscles not supplied by CN III are:

Superior oblique → CN IV.

Lateral rectus → CN VI.

2. Parasympathetic Fibres

The third cranial nerve also carries parasympathetic fibres to the eye.

These fibres ultimately supply the:

Sphincter pupillae → constricts the pupil.

Ciliary muscle → allows accommodation for near vision.

Therefore, a complete third nerve palsy may cause:

Dilated pupil.

Poor or absent pupillary reaction to light.

Loss of accommodation.

3. Location of the Third Nerve Nucleus

An important correction to the original note is that the oculomotor nucleus is located in the midbrain, not the pons.

It lies at approximately the level of the superior colliculus, close to the cerebral aqueduct.

Therefore:

CN III nucleus → midbrain.

CN VI nucleus → pons.

4. Main Features of Third Nerve Palsy

A complete third nerve palsy can produce a characteristic combination of:

Ptosis.

Dilated poorly reactive or unreactive pupil.

Impaired adduction.

Impaired elevation.

Impaired depression.

Eye resting in a “down and out” position.

These findings result from paralysis of most muscles supplied by CN III.

5. Ptosis

Ptosis occurs because the third nerve supplies the levator palpebrae superioris.

When this muscle is paralysed, the upper eyelid droops.

Therefore:

CN III palsy → levator weakness → ptosis.

In a complete palsy, the ptosis may be marked and may partially hide the abnormal position of the eye.

6. “Down and Out” Eye Position

In a complete third nerve palsy, most extraocular muscles are paralysed.

However, two muscles remain functional:

Lateral rectus → CN VI.

Superior oblique → CN IV.

The lateral rectus pulls the eye outward, while the superior oblique contributes to downward movement.

The result is the classic:

“Down and out” position of the affected eye.

7. Impaired Eye Movements

Because CN III supplies the medial, superior and inferior recti plus the inferior oblique, the affected eye has difficulty moving:

Medially.

Upward.

Downward.

Abduction is relatively preserved because the lateral rectus is supplied by CN VI.

8. Diplopia

Third nerve palsy usually causes diplopia because the two eyes are no longer aligned.

The exact direction in which diplopia is worst depends on the degree of weakness and which branches are affected.

In a complete palsy, the abnormal resting position is often obvious.

9. Pupillary Dilatation

The parasympathetic fibres responsible for pupillary constriction run superficially in the third nerve.

If these fibres are damaged, the pupil becomes:

Dilated.

Poorly reactive or unreactive to light.

A dilated pupil in the setting of a new third nerve palsy is particularly important because it may suggest a compressive lesion, especially an aneurysm.

10. Pupil-Involving Third Nerve Palsy

A painful third nerve palsy with a dilated pupil is a neurological emergency until a compressive aneurysm has been excluded.

The classic concern is a:

Posterior communicating artery aneurysm.

The aneurysm may compress the superficial parasympathetic fibres of CN III, producing early pupillary involvement.

Therefore:

Painful CN III palsy + dilated pupil → urgently exclude posterior communicating artery aneurysm.

11. Posterior Communicating Artery Aneurysm*

A posterior communicating artery aneurysm is one of the most important causes of third nerve palsy.

Typical findings may include:

Sudden severe headache.

Pain around the eye.

Ptosis.

Down-and-out eye.

Dilated poorly reactive pupil.

This presentation requires urgent vascular imaging and specialist assessment.

12. Microvascular Third Nerve Palsy*

Microvascular ischaemia is another common acquired cause, particularly in older adults with vascular risk factors.

Important associations include:

Diabetes mellitus.

Hypertension.

Other small-vessel disease.

Because the central motor fibres may be affected more than the superficial parasympathetic fibres, a microvascular palsy may be pupil-sparing.

13. Pupil-Sparing Third Nerve Palsy

A classic teaching pattern is:

Microvascular/diabetic CN III palsy → pupil often spared.

This is because the pupillary parasympathetic fibres lie superficially around the nerve and may escape central ischaemic damage.

However, pupil sparing is not absolute, and clinical assessment should not rely on this sign alone.

14. Demyelination

Demyelinating disease, including multiple sclerosis, can affect the oculomotor fascicles or associated brainstem pathways.

This is less common than microvascular or compressive causes but should be considered in younger patients or when other neurological symptoms are present.

15. Trauma

Head or orbital trauma may damage the third cranial nerve directly or indirectly.

Traumatic CN III palsy may be associated with:

Ptosis.

Ophthalmoplegia.

Pupillary abnormalities.

Other cranial nerve injuries.

The presence of multiple neurological deficits suggests more extensive injury.

16. Cavernous Sinus Disease

CN III passes through the lateral wall of the cavernous sinus.

Disease in this region can therefore affect the third nerve together with other cranial nerves.

Important neighbouring nerves include:

CN IV.

CN V1.

CN V2.

CN VI.

Therefore, a cavernous sinus lesion often causes multiple cranial neuropathies, not an isolated third nerve palsy.

17. Cavernous Sinus Thrombosis

Cavernous sinus thrombosis can cause:

Painful ophthalmoplegia.

Ptosis.

Proptosis.

Chemosis.

Sensory loss in V1/V2 distribution.

Fever or systemic infection signs, depending on cause.

It is an emergency requiring urgent treatment.

18. Orbital Tumour

An orbital tumour can impair ocular movements by:

Compressing cranial nerves.

Restricting extraocular muscles mechanically.

Causing proptosis.

Therefore, an orbital mass may produce ophthalmoplegia, but the pattern may not correspond neatly to a single cranial nerve palsy.

19. Thyroid Eye Disease

Thyroid eye disease can cause diplopia and restricted eye movement, but it is important to distinguish it from a true third nerve palsy.

In thyroid eye disease, the main problem is usually extraocular muscle enlargement and mechanical restriction, not direct CN III damage.

The inferior rectus and medial rectus are commonly affected.

Typical features may include:

Proptosis.

Lid retraction.

Restricted elevation.

Diplopia.

Exposure symptoms.

So thyroid eye disease is better considered a mimic of ocular motor nerve palsy rather than a classic cause of isolated CN III palsy.

20. Midbrain Lesions

Because the third nerve nucleus and fascicles are in the midbrain, lesions here may cause third nerve palsy together with other neurological abnormalities.

Possible causes include:

Stroke.

Tumour.

Demyelination.

Trauma.

Additional long-tract or cerebellar signs may help localise the lesion to the brainstem.

21. Third Nerve Palsy – Note Form

Cranial nerve: III, oculomotor nerve.

Nucleus: midbrain, not pons.

Muscles supplied: medial rectus, superior rectus, inferior rectus, inferior oblique and levator palpebrae superioris.

Muscles not supplied by CN III: lateral rectus and superior oblique.

Parasympathetic function: constricts pupil and assists accommodation.

Ptosis: caused by levator palpebrae weakness.

Eye position: down and out.

Eye movements impaired: upward, downward and medial movement.

Pupil: may be dilated and poorly reactive if parasympathetic fibres are involved.

*Microvascular causes: ** diabetes, hypertension and other vascular disease.

*Compressive cause: ** posterior communicating artery aneurysm.

Other causes: demyelination, trauma, cavernous sinus disease and midbrain lesions.

Orbital tumours: can cause ophthalmoplegia through compression or mechanical restriction.

Thyroid eye disease: usually a restrictive extraocular muscle disorder rather than a true isolated CN III palsy.

22. Important Clinical Example

If the patient has a right complete third nerve palsy:

Right eyelid is ptotic.

Right eye lies down and out.

Right eye cannot adduct normally.

Elevation and depression are impaired.

Right pupil may be dilated and unreactive if parasympathetic fibres are involved.

23. Pupil-Involving versus Pupil-Sparing – Note Form

Pupil-involving CN III palsy:

Think particularly about compressive pathology, especially a posterior communicating artery aneurysm.

Pupil-sparing CN III palsy:

Think particularly about microvascular ischaemia, such as diabetes.

However, this distinction is a useful clinical clue rather than an absolute rule.

24. Third, Fourth and Sixth Nerves – Quick Note Form

CN III: most extraocular muscles + levator + parasympathetic pupil fibres.

CN IV: superior oblique.

CN VI: lateral rectus.

CN III palsy: ptosis + down-and-out eye ± dilated pupil.

CN IV palsy: vertical diplopia worse looking down and in.

CN VI palsy: horizontal diplopia with impaired abduction.

Key Clinical Pattern

Remember third nerve palsy as:

CN III → most eye movements + eyelid elevation + pupil constriction.

Therefore:

Third nerve palsy → PTOSIS + DOWN-AND-OUT EYE + impaired adduction/elevation/depression ± DILATED PUPIL.

The most important emergency pattern is:

Painful third nerve palsy + dilated pupil → urgently exclude posterior communicating artery aneurysm.

And the important correction is:

The third nerve nucleus is in the MIDBRAIN, not the pons.

Medicine – Fourth Nerve Palsy

Fourth nerve palsy is dysfunction of the trochlear nerve, cranial nerve IV, which supplies the superior oblique muscle. Because the superior oblique is especially important for depressing the eye when it is adducted, trochlear nerve palsy classically causes vertical or oblique diplopia that is worse when looking down and in.

A useful memory rule is:

LR6 SO4, all the rest 3

meaning:

Lateral rectus → CN VI

Superior oblique → CN IV

Most other extraocular muscles → CN III

1. Function of the Fourth Cranial Nerve

The trochlear nerve supplies the superior oblique muscle.

The superior oblique has several actions, but clinically the most useful is:

Depression of the adducted eye.

It also contributes to:

Intorsion.

Abduction.

Therefore:

CN IV → superior oblique → especially helps the eye look down when turned inward.

2. Fourth Nerve Nucleus

The trochlear nucleus is located in the midbrain, approximately at the level of the inferior colliculus.

The fibres then cross before leaving the brainstem.

This means that the anatomy of a nuclear lesion is unusual compared with many other cranial nerves.

3. Dorsal Exit from the Brainstem

The trochlear nerve is unique because it is the only cranial nerve to emerge from the dorsal surface of the brainstem.

It exits from the posterior aspect of the midbrain and then wraps around the brainstem before passing forward.

This long and delicate intracranial course also makes it particularly vulnerable to trauma.

4. Trochlear Nerve Decussation

The fibres of the fourth nerve cross within the brainstem before emerging.

Therefore, a lesion of the trochlear nucleus affects the contralateral superior oblique muscle, whereas a lesion of the peripheral trochlear nerve affects the ipsilateral superior oblique.

For routine clinical examination, most isolated fourth nerve palsies are described according to the affected peripheral nerve and eye.

5. Effect of Fourth Nerve Palsy

When the superior oblique is weak, the affected eye cannot depress normally when it is adducted.

The patient therefore develops diplopia particularly during activities that require looking downward.

Typical examples include:

Reading.

Walking downstairs.

Looking down while eating.

Stepping off a kerb.

6. Diplopia

The diplopia is typically vertical or oblique, rather than purely horizontal.

It becomes most troublesome when looking:

Downward.

and

Toward the nose.

Therefore:

Fourth nerve palsy → diplopia worse on looking down and medially.

7. Why Looking Down and In Is Difficult

When the eye is adducted, the superior oblique is one of the main muscles responsible for depressing it.

If the superior oblique is paralysed:

Adducted eye + attempted downward gaze → impaired depression → vertical separation of the images.

This is why patients often notice symptoms when descending stairs or reading.

8. Head Tilt Compensation

Patients with fourth nerve palsy often adopt a compensatory head posture to reduce diplopia.

They may tilt their head away from the affected side.

This reduces the vertical misalignment caused by the weak superior oblique.

For example:

Right CN IV palsy → patient may tilt head to the left.

9. Bielschowsky Head-Tilt Test

The Bielschowsky head-tilt test can help identify a trochlear nerve palsy.

The vertical misalignment usually becomes worse when the head is tilted toward the affected side.

Therefore:

Right fourth nerve palsy → diplopia/hypertropia worsens with right head tilt.

This is an important clinical localisation sign.

10. Eye Position

The affected eye may appear slightly higher than the other eye, particularly in certain positions of gaze.

This is called hypertropia.

The misalignment is often most evident when the patient looks toward the opposite side and downward.

11. Vascular Causes*

Microvascular ischaemia is an important cause of acquired fourth nerve palsy, especially in older adults.

Important vascular risk factors include:

Diabetes mellitus.

Hypertension.

Other small-vessel vascular disease.

These palsies may occur suddenly and can sometimes improve spontaneously over weeks to months.

12. Diabetes Mellitus*

Diabetes can cause an ischaemic mononeuropathy affecting the trochlear nerve.

The patient may develop sudden vertical diplopia without major additional neurological deficits.

However, new cranial nerve palsy still needs assessment in the appropriate clinical context.

13. Trauma*

Head trauma is a particularly important cause of fourth nerve palsy.

The trochlear nerve is very thin and has a long intracranial course, making it vulnerable to shearing forces.

Trauma may cause:

Unilateral fourth nerve palsy.

or

Bilateral fourth nerve palsy.

Bilateral involvement should especially raise suspicion for significant head trauma.

14. Demyelination

Multiple sclerosis and other demyelinating diseases can affect the trochlear nucleus, fascicle, or nerve pathways.

This should be considered particularly in a younger patient with additional neurological symptoms.

15. Congenital Fourth Nerve Palsy

Fourth nerve palsy may be congenital.

Patients can compensate for many years by adopting a habitual head tilt.

The condition may only become obvious later when compensation fails or when the patient develops symptoms after illness, fatigue, or ageing.

16. Clues to Congenital Palsy

Features suggesting a longstanding congenital palsy may include:

Long-standing head tilt.

Facial asymmetry from chronic head posture.

Old photographs showing the same head tilt.

Large vertical fusion ability.

A patient may therefore first present in adulthood despite having had the condition since childhood.

17. Cavernous Sinus Syndrome

The trochlear nerve passes through the lateral wall of the cavernous sinus.

A cavernous sinus lesion can therefore affect CN IV along with several neighbouring cranial nerves.

These include:

CN III.

CN IV.

CN V1.

CN V2.

CN VI.

18. Cavernous Sinus Localisation

A cavernous sinus lesion may produce:

Diplopia.

Ophthalmoplegia.

Ptosis.

Reduced facial sensation in V1 or V2 distribution.

Because multiple nerves usually lie close together, an isolated fourth nerve palsy is less typical of a large cavernous sinus lesion than a combined cranial neuropathy.

19. Orbital Apex Syndrome

Disease at the orbital apex may affect several cranial nerves controlling eye movement.

These include:

CN III.

CN IV.

CN VI.

CN V1.

The optic nerve may also be involved.

Therefore, orbital apex disease may cause:

Ophthalmoplegia + visual loss + sensory abnormalities.

20. Fourth Nerve Palsy – Note Form

Cranial nerve: IV, trochlear nerve.

Muscle supplied: superior oblique.

Main clinical action: depresses the adducted eye.

Nucleus: midbrain.

Unique feature: only cranial nerve to emerge from the dorsal surface of the brainstem.

Another unique feature: fibres decussate before exiting.

Diplopia: vertical/oblique.

Diplopia worst: looking down and medially.

Common complaint: difficulty reading or walking downstairs.

Compensatory posture: head tilt away from affected side.

Bielschowsky test: vertical diplopia/misalignment worsens with head tilt toward affected side.

*Common acquired causes: ** vascular disease, diabetes and trauma.

Other causes: demyelination, congenital palsy, cavernous sinus syndrome and orbital apex syndrome.

21. Important Clinical Example

If the patient has a right fourth nerve palsy:

Right superior oblique is weak.

Right eye has difficulty looking down when adducted.

Vertical diplopia becomes worse when looking down and to the left.

Symptoms worsen with right head tilt.

The patient may compensate by tilting the head to the left.

22. Fourth versus Sixth Nerve Palsy – Quick Note Form

CN IV palsy: superior oblique weak.

CN VI palsy: lateral rectus weak.

CN IV diplopia: vertical/oblique.

CN VI diplopia: horizontal.

CN IV worst gaze: down and in.

CN VI worst gaze: toward affected side during abduction.

CN IV common functional complaint: difficulty descending stairs or reading.

CN VI common functional complaint: horizontal double vision, especially looking toward affected side.

Key Clinical Pattern

Remember fourth nerve palsy as:

CN IV → Superior Oblique → looks DOWN when eye is IN.

Therefore:

Fourth nerve palsy → vertical diplopia → worse looking down and medially → difficulty reading or descending stairs.

The important causes are:

Microvascular disease/diabetes + trauma + demyelination + congenital palsy + cavernous sinus disease + orbital apex disease.

And the classic anatomy points are:

Trochlear nucleus in midbrain + fibres cross + only cranial nerve to exit dorsally.

Medicine – Sixth Nerve Palsy

Sixth nerve palsy is dysfunction of the abducens nerve, cranial nerve VI, which supplies the lateral rectus muscle. Because the lateral rectus abducts the eye, sixth nerve palsy causes failure of abduction and produces horizontal diplopia, especially when looking toward the affected side.

A useful memory rule is:

LR6 SO4, all the rest 3

meaning:

Lateral rectus → CN VI

Superior oblique → CN IV

Most other extraocular muscles → CN III

1. Function of the Sixth Cranial Nerve

The abducens nerve supplies the lateral rectus muscle.

The lateral rectus moves the eye outward, away from the nose.

Therefore:

CN VI → lateral rectus → abduction of the eye.

2. Sixth Nerve Nucleus

The abducens nucleus is located in the pons, close to the floor of the fourth ventricle.

The fibres of the facial nerve loop around the abducens nucleus, forming the facial colliculus.

This anatomical relationship is important because pontine lesions may produce combined sixth and seventh cranial nerve abnormalities.

3. Effect of Sixth Nerve Palsy

When the lateral rectus is paralysed, the affected eye cannot abduct normally.

The unopposed action of the medial rectus, supplied by cranial nerve III, pulls the eye inward.

Therefore:

CN VI palsy → lateral rectus weakness → affected eye deviates medially.

This inward deviation is called esotropia.

4. Diplopia

Sixth nerve palsy typically causes horizontal diplopia.

The double vision becomes worse when the patient looks toward the affected side, because this requires contraction of the weak lateral rectus.

For example:

Right CN VI palsy → right eye cannot abduct → diplopia worse on looking right.

5. Diplopia at Distance

Diplopia may be particularly noticeable when looking at distant objects.

This is because distance fixation requires relatively greater divergence of the eyes.

Patients may turn their head toward the affected side to reduce diplopia.

6. Examination

Ask the patient to follow a target through the six cardinal positions of gaze.

In sixth nerve palsy, the affected eye shows:

Reduced or absent abduction.

The eye may be medially deviated in the primary position if the palsy is significant.

7. Raised Intracranial Pressure*

Raised intracranial pressure is an important cause of sixth nerve palsy.

The abducens nerve has a relatively long intracranial course and is vulnerable to stretching or displacement when intracranial pressure rises.

For this reason, sixth nerve palsy can occur even when the underlying pathology is not anatomically close to the sixth nerve nucleus.

8. False Localising Sign

A sixth nerve palsy caused by raised intracranial pressure is classically described as a false localising sign.

This means that the site of the cranial nerve palsy does not necessarily indicate the location of the underlying intracranial lesion.

For example, a distant mass lesion causing raised intracranial pressure may produce CN VI palsy through nerve stretching.

Therefore:

Raised ICP + CN VI palsy does not necessarily mean a pontine lesion.

9. Microvascular Causes*

Small-vessel ischaemia is a common cause of isolated sixth nerve palsy, particularly in older adults.

Important vascular risk factors include:

Diabetes mellitus.

Hypertension.

Other vascular disease.

These palsies are often termed microvascular cranial neuropathies.

10. Diabetes Mellitus

Diabetes can cause ischaemic injury to the sixth cranial nerve.

The patient may develop sudden-onset horizontal diplopia with an isolated abduction deficit.

Many presumed microvascular palsies improve spontaneously over weeks to months, but the diagnosis depends on the clinical context and exclusion of concerning alternative causes.

11. Demyelination

Multiple sclerosis and other demyelinating disorders can affect the sixth nerve nucleus, fascicle, or related brainstem pathways.

In a younger patient with sixth nerve palsy and additional neurological symptoms, demyelination should be considered.

12. Trauma*

Head trauma can injure the abducens nerve because of its long intracranial course and its passage over the petrous temporal bone.

Traumatic sixth nerve palsy may be unilateral or bilateral.

13. Cavernous Sinus Disease

The abducens nerve passes through the cavernous sinus, making it vulnerable to lesions in this region.

Causes may include:

Cavernous sinus thrombosis.

Tumours.

Aneurysmal or other vascular lesions.

Inflammatory disease.

14. Why Cavernous Sinus Lesions Are Important

Within the cavernous sinus, several cranial nerves lie close together.

These include:

CN III.

CN IV.

CN V1.

CN V2.

CN VI.

Therefore, a cavernous sinus lesion may produce a combination of:

Ophthalmoplegia.

Facial sensory loss.

Ptosis.

Diplopia.

An isolated sixth nerve palsy is possible, but multiple cranial nerve abnormalities make cavernous sinus disease more likely.

15. Orbital Apex Disease

Lesions at the orbital apex can affect several structures entering the orbit.

These may include:

CN II.

CN III.

CN IV.

CN VI.

Branches of CN V1.

Orbital apex disease may therefore produce ophthalmoplegia together with visual loss or sensory abnormalities.

16. Pontine Lesions

A lesion involving the abducens nucleus or fascicle within the pons can cause sixth nerve dysfunction.

Because of nearby structures, there may be additional neurological findings such as:

Facial weakness.

Gaze abnormalities.

Long-tract motor or sensory signs.

A nuclear lesion may produce more complex horizontal gaze abnormalities than an isolated peripheral sixth nerve palsy.

17. Sixth Nerve Palsy – Note Form

Cranial nerve: VI, abducens nerve.

Muscle supplied: lateral rectus.

Action: abducts the eye.

Nucleus: pons.

Palsy: affected eye fails to abduct.

Eye position: deviates medially because medial rectus is unopposed.

Diplopia: horizontal.

Diplopia worst: looking toward the affected side.

*Raised intracranial pressure: ** important cause and classic false localising sign.

*Microvascular causes: ** diabetes, hypertension and other vascular disease.

Other causes: demyelination, trauma, cavernous sinus disease and orbital apex disease.

18. Important Clinical Example

If the patient has a right sixth nerve palsy:

Right lateral rectus is weak.

Right eye cannot move fully to the right.

Right eye tends to deviate medially.

Horizontal diplopia becomes worse when looking to the right.

19. Localisation Clues

Isolated CN VI palsy in an older diabetic patient → consider microvascular ischaemia.

CN VI palsy + headache/papilloedema → consider raised intracranial pressure.

CN VI + III/IV/V abnormalities → consider cavernous sinus lesion.

CN VI + visual loss/multiple orbital nerve deficits → consider orbital apex disease.

CN VI + other brainstem signs → consider pontine lesion or demyelination.

Key Clinical Pattern

Remember sixth nerve palsy as:

CN VI → lateral rectus → abduction.

Therefore:

Sixth nerve palsy → eye cannot abduct → eye turns inward → horizontal diplopia worse on looking toward the affected side.

The most important causes to remember are:

Raised intracranial pressure + microvascular disease/diabetes + demyelination + trauma + cavernous sinus disease + orbital apex disease.

And the classic exam phrase is:

Raised ICP causing sixth nerve palsy = false localising sign.

Medicine – Facial Nerve (Cranial Nerve VII)

The facial nerve, cranial nerve VII, is a mixed cranial nerve with motor, sensory, special sensory, and parasympathetic functions. A useful way to remember its major functions is:

Face + Ear + Taste + Tears + Saliva.

Its most obvious function is controlling the muscles of facial expression, but it also supplies the stapedius muscle, carries taste from the anterior two-thirds of the tongue, and provides parasympathetic fibres to the lacrimal and salivary glands.

1. Motor Supply to the Face

The facial nerve provides motor innervation to the muscles of facial expression.

These muscles allow a person to:

Raise the eyebrows.

Close the eyes tightly.

Smile.

Show the teeth.

Puff out the cheeks.

Frown.

Weakness of these movements is therefore an important sign of facial nerve dysfunction.

2. Upper versus Lower Facial Muscles

The cortical control of the facial nucleus is clinically important.

The part of the facial nucleus controlling the upper face receives corticobulbar input from both cerebral hemispheres.

The part controlling the lower face receives predominantly contralateral cortical input.

This explains the major difference between upper motor neurone and lower motor neurone facial palsy.

3. Motor Supply to Stapedius

The facial nerve supplies the stapedius muscle in the middle ear.

Stapedius normally reduces excessive movement of the stapes in response to loud sounds.

Facial nerve damage proximal to the stapedius branch can therefore cause hyperacusis, meaning that ordinary sounds are perceived as abnormally loud or uncomfortable.

Therefore:

CN VII lesion → stapedius paralysis → hyperacusis.

4. Sensory Supply to the Ear

The facial nerve carries a small amount of general somatic sensation from part of the external auditory canal and external ear.

This sensory territory is small because most sensation around the ear is supplied by other nerves.

Nevertheless, the association of CN VII with the external auditory canal becomes particularly relevant in Ramsay Hunt syndrome.

5. Taste

Taste fibres from the anterior two-thirds of the tongue travel through the chorda tympani, a branch associated with the facial nerve.

Therefore, a facial nerve lesion proximal to the origin of the chorda tympani can produce:

Reduced or absent taste from the anterior two-thirds of the tongue on the affected side.

6. Chorda Tympani

The chorda tympani has two particularly important functions.

It carries:

Taste fibres from the anterior two-thirds of the tongue.

and

Parasympathetic secretomotor fibres to the submandibular and sublingual salivary glands.

Therefore, CN VII is involved not only in taste but also in salivation.

7. Lacrimal Gland

Parasympathetic fibres associated with the facial nerve supply the lacrimal gland through the greater petrosal nerve and associated pathways.

These fibres stimulate tear production.

A sufficiently proximal facial nerve lesion can therefore impair lacrimation and contribute to dryness of the eye.

8. Salivary Glands

The facial nerve also provides parasympathetic secretomotor fibres to:

Submandibular gland.

Sublingual gland.

The parotid gland is not supplied parasympathetically by the facial nerve.

Its secretomotor parasympathetic supply comes from the glossopharyngeal nerve, CN IX.

This distinction is clinically important because the facial nerve passes through the parotid gland but does not provide its secretomotor innervation.

9. Facial Nerve Branches

After leaving the stylomastoid foramen, the facial nerve enters the parotid gland and divides into five major terminal motor branches.

These are:

Temporal.

Zygomatic.

Buccal.

Marginal mandibular.

Cervical.

10. Correction to the Original Branch List

The original list gives:

Temporal, ophthalmic, maxillary, mandibular and cervical.

This mixes the branches of the facial nerve with divisions of the trigeminal nerve, CN V.

The correct five terminal branches of CN VII are:

Temporal → Zygomatic → Buccal → Marginal mandibular → Cervical.

11. Easy Memory for the Five Branches

A traditional mnemonic is:

To Zanzibar By Motor Car

T → Temporal

Z → Zygomatic

B → Buccal

M → Marginal mandibular

C → Cervical

These are motor branches supplying the muscles of facial expression.

12. Trigeminal Nerve Branches – Important Distinction

The terms ophthalmic, maxillary and mandibular belong primarily to the trigeminal nerve, cranial nerve V.

They are:

V1 → Ophthalmic.

V2 → Maxillary.

V3 → Mandibular.

Therefore:

CN V → Ophthalmic, Maxillary, Mandibular.

CN VII → Temporal, Zygomatic, Buccal, Marginal mandibular, Cervical.

13. Facial Nerve Palsy

Facial weakness can result from either an:

Upper motor neurone lesion.

or

Lower motor neurone lesion.

The pattern of facial weakness helps localise the lesion.

14. Upper Motor Neurone Facial Palsy

An UMN facial palsy results from damage to corticobulbar pathways above the facial nucleus.

Because the upper facial muscles receive bilateral cortical innervation, they are relatively preserved in a unilateral UMN lesion.

Therefore, an UMN lesion classically causes:

Contralateral lower facial weakness with relative forehead sparing.

15. Forehead Sparing

Suppose a patient has a left cerebral stroke affecting corticobulbar fibres.

The patient may develop:

Right lower facial weakness.

However, the patient may still be able to wrinkle the forehead and close the eyes relatively well because the upper facial nucleus receives bilateral cortical input.

Therefore:

Forehead sparing → think UMN lesion.

16. Causes of UMN Facial Weakness

Important causes include:

Stroke.

Multiple sclerosis.

Intracranial tumour or other central structural lesions.

These lesions affect the corticobulbar pathways rather than the peripheral facial nerve itself.

17. Stroke

Stroke is an important cause of acute UMN facial weakness.

The typical pattern is:

Contralateral lower facial weakness + forehead relatively spared.

Other neurological deficits may occur simultaneously, such as:

Arm or leg weakness.

Dysarthria.

Sensory abnormalities.

Aphasia, depending on the site of the stroke.

18. Multiple Sclerosis

Multiple sclerosis can produce facial weakness when demyelinating lesions involve central corticobulbar pathways or the facial nerve pathway within the brainstem.

The exact clinical pattern therefore depends on the location of the demyelinating plaque.

Other neurological manifestations of MS may coexist.

19. Lower Motor Neurone Facial Palsy

An LMN facial palsy occurs when the facial nucleus in the pons or the facial nerve itself is affected.

The lesion causes weakness of the entire ipsilateral half of the face.

Therefore, the patient may be unable to:

Wrinkle the forehead.

Close the eye tightly.

Smile normally.

Puff out the cheek.

20. LMN Facial Palsy and the Forehead

Unlike an UMN lesion, an LMN lesion does not spare the forehead.

Therefore:

Whole ipsilateral face weak → LMN facial palsy.

Contralateral lower face weak with forehead spared → UMN facial palsy.

This is one of the most useful bedside distinctions.

21. Bell Palsy

Bell palsy is an acute idiopathic peripheral facial nerve palsy and is one of the most common causes of an isolated LMN facial palsy.

It usually develops rapidly, often over hours.

The patient develops unilateral weakness involving both the upper and lower face.

22. Features of Bell Palsy

Patients may have:

Unilateral facial weakness.

Inability to close the affected eye completely.

Drooping of the corner of the mouth.

Difficulty drinking because fluid escapes from the mouth.

Reduced taste, depending on lesion location.

Hyperacusis, depending on involvement of the stapedius branch.

Some patients experience discomfort around the ear.

23. Eye Protection in Bell Palsy

Inability to close the eyelid can expose the cornea.

This may lead to:

Corneal dryness.

Exposure keratitis.

Corneal ulceration in severe cases.

Therefore, eye protection and lubrication are important when eye closure is impaired.

24. Ramsay Hunt Syndrome

Ramsay Hunt syndrome is caused by reactivation of varicella-zoster virus involving the facial nerve, usually around the geniculate ganglion.

It can produce a severe LMN facial palsy.

25. Features of Ramsay Hunt Syndrome

The classic pattern includes:

Ipsilateral LMN facial weakness.

Severe ear pain.

Vesicular eruption in or around the external auditory canal or pinna.

Vestibulocochlear involvement may also produce:

Hearing loss.

Tinnitus.

Vertigo.

Therefore:

Facial palsy + painful ear vesicles → Ramsay Hunt syndrome.

26. Acoustic Neuroma

The older term acoustic neuroma generally refers to a vestibular schwannoma.

This is a benign tumour usually arising from the vestibular component of CN VIII.

As the tumour enlarges, it may compress nearby cranial nerves, including CN VII.

The more typical early presentation is:

Progressive unilateral sensorineural hearing loss.

Unilateral tinnitus.

Imbalance.

Facial weakness tends to occur with larger lesions rather than being the usual initial manifestation.

27. Parotid Tumours

The facial nerve passes through the parotid gland, where it divides into its terminal branches.

A parotid tumour can therefore compress or invade the facial nerve and produce an LMN facial palsy.

Facial weakness associated with a parotid mass is particularly concerning for malignant involvement and requires investigation.

28. Guillain–Barré Syndrome

Guillain–Barré syndrome can involve the facial nerves.

Facial weakness is frequently bilateral, although it may initially be asymmetric.

Other features may include:

Ascending limb weakness.

Areflexia.

Sensory symptoms.

Autonomic dysfunction.

Respiratory weakness.

Therefore:

Bilateral LMN facial weakness + areflexic ascending weakness → consider GBS.

29. Examination of the Facial Nerve

To examine the motor component of CN VII, ask the patient to:

Raise the eyebrows.

Wrinkle the forehead.

Close the eyes tightly.

Show the teeth.

Smile.

Puff out the cheeks.

These movements allow assessment of different facial muscle groups and help determine whether weakness involves the upper face, lower face, or both.

30. UMN versus LMN Facial Palsy – Note Form

UMN lesion: corticobulbar pathway above facial nucleus.

LMN lesion: facial nucleus or facial nerve.

UMN weakness: mainly contralateral lower face.

LMN weakness: entire ipsilateral half of face.

UMN forehead: relatively spared.

LMN forehead: weak.

UMN eye closure: relatively preserved.

LMN eye closure: impaired.

UMN causes: stroke, MS, intracranial tumour.

LMN causes: Bell palsy, Ramsay Hunt syndrome, vestibular schwannoma, parotid tumour and GBS.

31. Facial Nerve – Note Form

Cranial nerve: VII.

Motor: muscles of facial expression.

Ear: supplies stapedius.

Stapedius paralysis: may cause hyperacusis.

General sensation: small area of external auditory canal/external ear.

Taste: anterior two-thirds of tongue via chorda tympani.

Tears: parasympathetic supply to lacrimal gland.

Saliva: parasympathetic supply to submandibular and sublingual glands.

Five terminal branches: temporal, zygomatic, buccal, marginal mandibular and cervical.

Bell palsy: acute LMN facial palsy affecting the whole ipsilateral face.

Ramsay Hunt: facial palsy + painful vesicles around/in the ear ± hearing or vestibular symptoms.

Stroke: usually contralateral lower facial weakness with forehead sparing.

GBS: may produce bilateral LMN facial weakness.

Key Clinical Pattern

Remember the main functions of CN VII as:

FACE + EAR + TASTE + TEARS + SALIVA.

The five terminal branches are:

Temporal → Zygomatic → Buccal → Marginal mandibular → Cervical.

The most important localisation rule is:

UMN lesion → contralateral LOWER face weak + forehead spared.

LMN lesion → ipsilateral WHOLE face weak + forehead involved.

And remember:

Bell palsy → isolated LMN facial palsy.

Ramsay Hunt → LMN facial palsy + painful ear vesicles.

Stroke → UMN facial weakness with forehead sparing.

Medicine – Vestibulocochlear Nerve (Cranial Nerve VIII): Rinne’s and Weber’s Tests

The vestibulocochlear nerve, cranial nerve VIII, has two main components:

Cochlear division → hearing.

Vestibular division → balance.

Bedside assessment of hearing commonly includes Rinne’s test and Weber’s test, both performed with a tuning fork, typically 512 Hz.

1. Rinne’s Test

Rinne’s test compares air conduction (AC) with bone conduction (BC) in each ear separately.

Normally, sound is transmitted more efficiently through the external auditory canal and middle ear than through direct vibration of the skull.

Therefore, in a normal ear:

Air conduction > bone conduction.

This is called Rinne positive.

2. Normal Rinne Test

In a normal ear:

AC > BC.

The patient hears the tuning fork longer or louder when it is held beside the ear than when it is placed on the mastoid process.

This is a normal finding.

3. Sensorineural Deafness and Rinne’s Test

In sensorineural hearing loss, both air and bone conduction are reduced because the cochlea or auditory nerve is impaired.

However, the normal relationship between the two pathways remains:

AC > BC.

Therefore, Rinne remains positive.

So:

Normal ear → Rinne positive.

Sensorineural deafness → Rinne positive.

The difference is that overall hearing is reduced in sensorineural loss.

4. Conductive Deafness and Rinne’s Test

In conductive hearing loss, sound transmission through the external or middle ear is impaired.

Bone conduction bypasses these structures and may therefore be heard better than air conduction.

Thus:

BC > AC.

This is called Rinne negative.

Therefore:

Conductive hearing loss → Rinne negative.

5. Rinne Test – Quick Note Form

Normal: AC > BC → Rinne positive.

Sensorineural hearing loss: AC > BC → Rinne positive, but hearing is reduced overall.

Conductive hearing loss: BC > AC → Rinne negative.

6. Weber’s Test

Weber’s test compares how sound is perceived between the two ears.

A vibrating tuning fork is placed in the midline, usually on the forehead or vertex of the skull.

The patient is asked whether the sound is heard:

Equally in both ears.

or

Louder in one ear.

7. Normal Weber Test

In a person with normal hearing, the sound is heard equally in both ears.

This is described as:

Weber does not lateralise.

8. Conductive Hearing Loss and Weber’s Test

In unilateral conductive hearing loss, Weber’s test lateralises to the affected ear.

So:

Conductive deafness → sound louder in the abnormal ear.

This may seem counterintuitive, but external environmental sounds are reduced in that ear, so bone-conducted sound is perceived relatively more strongly.

9. Sensorineural Hearing Loss and Weber’s Test

In unilateral sensorineural hearing loss, Weber’s test lateralises to the normal or better-hearing ear.

So:

Sensorineural deafness → sound louder in the opposite ear.

The affected cochlea or auditory nerve cannot perceive the bone-conducted vibration normally.

10. Meaning of Weber Lateralisation

If Weber’s test is heard louder on the right side, there are two main possibilities:

Right conductive hearing loss.

or

Left sensorineural hearing loss.

Similarly, if the sound is louder on the left:

Left conductive hearing loss.

or

Right sensorineural hearing loss.

This is why Weber should be interpreted together with Rinne’s test.

11. Combining Rinne and Weber

A useful bedside approach is to use both tests together.

If Weber lateralises to the right and Rinne is negative on the right:

Right conductive hearing loss.

If Weber lateralises to the right and Rinne remains positive on both sides:

Left sensorineural hearing loss is more likely.

12. Conductive Hearing Loss – Typical Pattern

In unilateral conductive hearing loss:

Rinne on affected side → negative, BC > AC.

Weber → lateralises to affected side.

Example:

Right conductive deafness → right Rinne negative + Weber louder on right.

13. Sensorineural Hearing Loss – Typical Pattern

In unilateral sensorineural hearing loss:

Rinne → positive on both sides, AC > BC.

Weber → lateralises to the better-hearing ear.

Example:

Right sensorineural deafness → Rinne positive bilaterally + Weber louder on left.

14. Important Limitation of Rinne’s Test

In very severe unilateral sensorineural deafness, a false-negative Rinne test may occasionally occur.

This happens because bone-conducted vibration placed on the mastoid of the deaf ear may cross the skull and be heard by the opposite normal cochlea.

Therefore, bedside tuning-fork tests are useful screening tools but do not replace formal audiometry when significant hearing loss is suspected.

15. Vestibulocochlear Nerve – Note Form

Cranial nerve VIII: vestibulocochlear nerve.

Cochlear division: hearing.

Vestibular division: balance.

Rinne test: compares air conduction with bone conduction.

Normal Rinne: AC > BC.

Sensorineural loss: AC > BC, so Rinne remains positive.

Conductive loss: BC > AC, so Rinne is negative.

Weber test: tuning fork placed in middle of forehead or vertex.

Normal Weber: sound heard equally on both sides.

Conductive loss: Weber lateralises to the affected ear.

Sensorineural loss: Weber lateralises to the normal/better ear.

Key Clinical Pattern

Remember:

Rinne = compare AIR with BONE.

Weber = compare RIGHT with LEFT.

Normal:

Rinne positive (AC > BC)

Weber central

Conductive hearing loss:

Rinne negative on affected side (BC > AC)

Weber goes TO the affected ear

Sensorineural hearing loss:

Rinne positive (AC > BC)

Weber goes AWAY from the affected ear

Easy Memory Rule

Conductive → Weber goes TO the bad ear.

Sensorineural → Weber goes to the GOOD ear.

Medicine – Causes of Deafness

Deafness, or hearing loss, can be broadly divided into conductive hearing loss and sensorineural hearing loss. Conductive hearing loss occurs when sound cannot be transmitted efficiently through the external or middle ear, whereas sensorineural hearing loss results from damage to the cochlea, the vestibulocochlear nerve, or central auditory pathways.

An asterisk (*) below signifies a common cause.

1. Conductive Hearing Loss

Conductive hearing loss occurs when sound transmission through the external auditory canal, tympanic membrane, or middle-ear ossicles is impaired.

The cochlea and auditory nerve may remain functionally intact.

Typical causes include ear wax and middle-ear disease.

2. Ear Wax*

Impacted cerumen, or ear wax, is a common and usually reversible cause of conductive hearing loss.

Wax may obstruct the external auditory canal and prevent sound waves from reaching the tympanic membrane effectively.

Patients may complain of:

Reduced hearing.

Blocked-ear sensation.

Tinnitus.

Occasionally discomfort may occur.

Removal of the impacted wax usually restores hearing if no additional pathology is present.

3. Middle-Ear Disease*

Middle-ear disease is another common cause of conductive hearing loss.

Sound transmission may be impaired by fluid, infection, tympanic membrane abnormalities, or ossicular dysfunction.

Important examples include:

Otitis media.

Otitis media with effusion, or glue ear.

Tympanic membrane perforation.

Cholesteatoma.

Ossicular fixation or disruption.

The exact degree of hearing loss depends on the extent of mechanical impairment.

4. Sensorineural Hearing Loss

Sensorineural hearing loss results from damage to the inner ear, particularly the cochlea, or from dysfunction of the vestibulocochlear nerve and central auditory pathways.

Unlike many conductive causes, sensorineural hearing loss is often permanent.

It may be divided broadly into:

Cochlear causes.

Nerve or retrocochlear causes.

Congenital causes.

5. Cochlear Causes

Cochlear hearing loss results from damage to structures within the inner ear.

Important causes include:

Otosclerosis.

Noise-induced hearing loss.

Drug-induced ototoxicity.

Ménière disease.

Paget disease.

6. Otosclerosis*

Otosclerosis is caused by abnormal bone remodelling around the stapes and otic capsule.

Classically, fixation of the stapes footplate causes conductive hearing loss rather than purely sensorineural hearing loss.

However, if the disease extends into the cochlea, a sensorineural component may develop.

Therefore, although older notes may place otosclerosis under cochlear sensorineural causes, the classic presentation is:

Stapes fixation → conductive hearing loss.

7. Noise-Induced Hearing Loss*

Noise-induced hearing loss is a common cause of sensorineural deafness.

Prolonged or repeated exposure to loud noise damages cochlear hair cells.

Examples include:

Industrial noise.

Loud music.

Firearms.

Heavy machinery.

The hearing loss is usually bilateral and commonly affects high frequencies first.

8. Drug-Induced Hearing Loss

A number of drugs and toxins are ototoxic and may damage the cochlea or vestibular apparatus.

Important examples include:

Aminoglycoside antibiotics, such as gentamicin.

Loop diuretics, such as furosemide.

Certain chemotherapy drugs, especially cisplatin.

The original note also lists lead, which is better considered a toxic heavy-metal exposure rather than a drug.

9. Aminoglycosides

Aminoglycosides can damage cochlear and vestibular hair cells.

Examples include:

Gentamicin.

Amikacin.

Streptomycin.

Risk increases with higher cumulative exposure, renal impairment, and concurrent use of other ototoxic drugs.

Hearing loss may be permanent.

10. Furosemide

Furosemide is a loop diuretic that can cause ototoxicity, particularly when given in high doses or rapidly intravenously.

The risk may increase when combined with other ototoxic medications.

Hearing impairment may be reversible or permanent depending on severity.

11. Lead Exposure

Lead toxicity can damage the nervous system and may contribute to hearing impairment.

Lead is therefore best remembered as a toxic environmental cause rather than a conventional drug-induced cause.

12. Ménière Disease

Ménière disease causes fluctuating sensorineural hearing loss due to abnormal inner-ear fluid regulation, classically associated with endolymphatic hydrops.

The characteristic clinical combination is:

Episodic vertigo.

Fluctuating sensorineural hearing loss.

Tinnitus.

Aural fullness.

Hearing loss may become progressively permanent after repeated attacks.

13. Paget Disease

Paget disease of bone can involve the skull and temporal bone.

Abnormal bone remodelling may interfere with the auditory apparatus and produce:

Conductive hearing loss.

Sensorineural hearing loss.

or

Mixed hearing loss.

Therefore, hearing impairment in Paget disease is not exclusively cochlear.

14. Nerve or Retrocochlear Causes

Hearing loss may also result from damage to the vestibulocochlear nerve, CN VIII, or nearby central auditory pathways.

Important causes include:

Vestibular schwannoma.

Head trauma.

Meningitis.

15. Acoustic Neuroma

The traditional term acoustic neuroma usually refers to a vestibular schwannoma.

This is a benign tumour arising from Schwann cells, most commonly from the vestibular division of cranial nerve VIII.

A typical presentation is:

Progressive unilateral sensorineural hearing loss.

Unilateral tinnitus.

Imbalance.

Large tumours may also compress neighbouring cranial nerves or the brainstem.

16. Head Trauma

Head trauma can cause hearing loss by damaging:

The cochlea.

The vestibulocochlear nerve.

The temporal bone.

Central auditory pathways.

Temporal bone fractures may produce conductive, sensorineural, or mixed hearing loss depending on the structures damaged.

17. Meningitis

Meningitis is an important cause of acquired sensorineural hearing loss.

Inflammation can damage the cochlea or vestibulocochlear nerve.

Hearing impairment may be:

Unilateral or bilateral.

Temporary or permanent.

Bacterial meningitis is particularly important because severe hearing loss may occur after recovery from the acute infection.

18. Congenital Hearing Loss

Congenital hearing loss is present at birth or develops very early in life.

It may be caused by:

Genetic disorders.

Congenital infections.

Structural abnormalities of the inner ear.

Prematurity or perinatal complications.

Genetic causes account for a large proportion of congenital sensorineural hearing loss.

19. Congenital Infections

Important congenital infections associated with sensorineural hearing loss include:

Cytomegalovirus.

Rubella.

Other congenital infections can also cause auditory damage depending on the clinical context.

Early detection is essential because hearing impairment can significantly affect speech and language development.

20. Causes of Deafness – Note Form

Conductive hearing loss: impaired sound transmission through the external or middle ear.

Ear wax:* common, reversible obstruction of the external auditory canal.

Middle-ear disease:* otitis media, glue ear, tympanic membrane disease, cholesteatoma, or ossicular dysfunction.

Sensorineural hearing loss: damage to the cochlea, auditory nerve, or central auditory pathways.

Otosclerosis:* classically causes conductive hearing loss due to stapes fixation; cochlear involvement may add a sensorineural component.

Noise-induced hearing loss:* cochlear hair-cell damage from prolonged loud-noise exposure.

Drug-induced: aminoglycosides and furosemide are important ototoxic drugs.

Lead: toxic heavy-metal exposure that may contribute to hearing impairment.

Ménière disease: vertigo + fluctuating sensorineural hearing loss + tinnitus + aural fullness.

Paget disease: may produce conductive, sensorineural, or mixed hearing loss.

Acoustic neuroma: more accurately vestibular schwannoma; usually causes progressive unilateral sensorineural hearing loss and tinnitus.

Head trauma: may damage the cochlea, CN VIII, temporal bone, or central auditory pathways.

Meningitis: important acquired cause of sensorineural deafness, particularly after bacterial meningitis.

Congenital: genetic disorders, congenital infections, structural abnormalities, and perinatal causes.

Key Clinical Pattern

Remember the first division as:

Conductive deafness → external or middle-ear problem.

Sensorineural deafness → cochlea or auditory nerve problem.

The common conductive causes are:

Ear wax + middle-ear disease.

The major sensorineural causes to remember are:

Noise exposure + ototoxic drugs + Ménière disease + vestibular schwannoma + meningitis + congenital causes.

A particularly useful correction is:

Otosclerosis classically causes conductive hearing loss because of stapes fixation, although advanced cochlear involvement can produce a sensorineural component.

Medicine – Causes of Vertigo

Vertigo is the false sensation that the patient or surroundings are moving, usually described as spinning, tilting, or rotating. It results from dysfunction of the vestibular system and is broadly divided into peripheral vertigo, arising from the inner ear or vestibular nerve, and central vertigo, arising from the brainstem or cerebellar pathways.

A useful first step is:

Peripheral vertigo → inner ear/vestibular apparatus.

Central vertigo → brainstem or cerebellum.

1. Peripheral Vertigo

Peripheral vertigo results from disease affecting the labyrinth, semicircular canals, vestibular apparatus, or vestibular nerve.

It is often associated with:

Severe spinning sensation.

Nausea and vomiting.

Positional worsening.

Horizontal or rotatory nystagmus.

Depending on the cause, hearing loss or tinnitus may also occur.

2. Viral Vestibular Disease

A common peripheral cause is viral vestibular neuritis.

This typically presents with:

Acute severe vertigo.

Nausea and vomiting.

Unsteadiness.

No major hearing loss.

Symptoms may persist for hours to days.

The disorder is thought to involve inflammation of the vestibular nerve, often following or associated with a viral illness.

3. Labyrinthitis

If acute vertigo occurs together with hearing loss, the diagnosis may be labyrinthitis rather than isolated vestibular neuritis.

This distinction is useful:

Vestibular neuritis → vertigo without significant hearing loss.

Labyrinthitis → vertigo + hearing impairment.

4. Ménière Disease

Ménière disease is an important peripheral cause of recurrent vertigo.

The classical pattern is:

Episodic vertigo.

Fluctuating sensorineural hearing loss.

Tinnitus.

Aural fullness or pressure.

The condition is associated with abnormal regulation of endolymph within the inner ear.

5. Benign Paroxysmal Positional Vertigo

Benign paroxysmal positional vertigo (BPPV) is one of the most common causes of peripheral vertigo.

It produces brief episodes of vertigo triggered by changes in head position, such as:

Turning over in bed.

Looking upward.

Getting out of bed.

Bending down.

Episodes usually last seconds rather than hours.

6. Mechanism of BPPV

BPPV is usually caused by displaced otoconia entering a semicircular canal, most commonly the posterior canal.

Head movement causes abnormal movement of these particles, stimulating the vestibular system and producing vertigo.

Therefore:

Displaced otoconia → abnormal semicircular canal stimulation → positional vertigo.

7. Chronic Otitis Media

Chronic middle-ear disease can occasionally cause vertigo, particularly when infection or inflammation extends toward the labyrinth or produces complications.

Therefore, chronic otitis media can be associated with peripheral vertigo, but uncomplicated otitis media itself is not among the most typical causes of isolated vertigo.

8. Internal Auditory Artery Occlusion

Occlusion of the internal auditory artery, also called the labyrinthine artery, can cause sudden vestibular dysfunction.

Patients may develop:

Sudden severe vertigo.

Sudden sensorineural hearing loss.

This is important because vascular inner-ear disease can resemble other peripheral vestibular disorders.

9. Central Vertigo

Central vertigo results from disease affecting the brainstem, cerebellum, or central vestibular pathways.

It is especially important because some causes are potentially life-threatening.

Central vertigo may be associated with other neurological abnormalities such as:

Diplopia.

Dysarthria.

Limb weakness.

Sensory loss.

Severe ataxia.

Cranial nerve abnormalities.

10. Stroke

Stroke is one of the most important central causes of acute vertigo.

Posterior-circulation ischaemia involving the:

Brainstem.

Cerebellum.

can present with vertigo and imbalance.

A stroke should be considered particularly when vertigo is associated with new focal neurological findings or severe inability to stand or walk.

11. Posterior Circulation Stroke

Cerebellar or brainstem infarction may produce:

Sudden vertigo.

Nystagmus.

Vomiting.

Severe gait or truncal ataxia.

Additional symptoms may include:

Diplopia.

Dysarthria.

Dysphagia.

Weakness or sensory disturbance.

The absence of obvious limb weakness does not completely exclude a posterior-circulation stroke.

12. Alcohol

Acute alcohol intoxication can disturb cerebellar and vestibular function.

This may cause:

Dizziness or vertigo.

Nystagmus.

Ataxia.

Poor coordination.

Therefore, alcohol is an important toxic/metabolic contributor to central vestibular symptoms.

13. Drugs

Several medications can produce dizziness, vertigo, ataxia, or vestibular toxicity.

Examples include some:

Anticonvulsants.

Sedatives.

Aminoglycoside antibiotics.

Certain chemotherapy agents.

A careful medication history is therefore important in a patient presenting with vertigo.

14. Multiple Sclerosis

Multiple sclerosis can produce central vertigo when demyelinating plaques involve the brainstem or cerebellar vestibular pathways.

Other features suggesting MS may include:

Optic neuritis.

Diplopia.

Internuclear ophthalmoplegia.

Sensory symptoms.

Upper motor neurone signs.

Ataxia.

15. Space-Occupying Lesion

A space-occupying lesion, such as a tumour affecting the brainstem or cerebellum, can produce vertigo.

Examples include:

Glioma.

Cerebellar tumour.

Posterior-fossa mass.

Symptoms may be gradual and progressive rather than suddenly episodic.

16. Migraine

Vestibular migraine is an important and relatively common cause of recurrent vertigo.

Vertigo may occur:

With headache.

Before headache.

Without headache during some attacks.

Patients may also have typical migraine features such as photophobia, phonophobia, visual aura, or a previous migraine history.

17. Hypoglycaemia

Hypoglycaemia can cause dizziness, weakness, confusion, and unsteadiness.

True rotational vertigo is less specific, but hypoglycaemia should be considered in an acutely unwell patient with neurological or autonomic symptoms.

Associated features may include:

Sweating.

Tremor.

Palpitations.

Confusion.

Reduced consciousness.

18. Peripheral Vertigo – Note Form

BPPV: brief positional attacks, typically seconds, triggered by head movement.

Vestibular neuritis: acute prolonged vertigo, usually without hearing loss.

Labyrinthitis: vertigo with hearing impairment.

Ménière disease: episodic vertigo + fluctuating hearing loss + tinnitus + aural fullness.

Chronic otitis media: may cause vertigo when complicated by inner-ear involvement.

Internal auditory/labyrinthine artery occlusion: sudden vertigo often with sudden hearing loss.

19. Central Vertigo – Note Form

Stroke: sudden vertigo with possible brainstem or cerebellar neurological signs.

Alcohol: intoxication may cause vertigo, nystagmus and ataxia.

Drugs: sedative, anticonvulsant or vestibulotoxic medications can cause symptoms.

Multiple sclerosis: demyelinating brainstem or cerebellar lesions.

Space-occupying lesion: brainstem or cerebellar tumour, such as glioma.

Migraine: vestibular migraine causes recurrent vertigo, sometimes without headache.

Hypoglycaemia: metabolic cause of dizziness/unsteadiness and occasionally vertigo-like symptoms.

20. Peripheral versus Central Vertigo – Quick Note Form

Peripheral vertigo: usually more intense spinning and nausea.

Central vertigo: may be less intensely spinning but is more likely to have neurological signs.

Peripheral hearing symptoms: may occur, especially Ménière disease, labyrinthitis, or labyrinthine artery occlusion.

Central hearing symptoms: generally less typical, depending on lesion location.

Peripheral neurological deficits: usually absent.

Central neurological deficits: may include diplopia, dysarthria, weakness, sensory loss or marked ataxia.

Peripheral causes: BPPV, vestibular neuritis, labyrinthitis, Ménière disease.

Central causes: stroke, MS, migraine, tumours, drugs or toxins.

Key Clinical Pattern

The easiest way to remember the common causes is:

Peripheral vertigo → BPPV + vestibular neuritis/labyrinthitis + Ménière disease.

Central vertigo → stroke + MS + vestibular migraine + posterior-fossa lesions.

A very useful clinical clue is:

Vertigo + hearing symptoms → think peripheral inner-ear disease.

Vertigo + focal neurological signs or severe central ataxia → think central cause, especially posterior-circulation stroke.

Medicine – Bulbar Palsy vs Pseudobulbar Palsy

Bulbar palsy and pseudobulbar palsy can both cause dysarthria and dysphagia, but they arise from lesions at different levels of the motor pathway. The simplest distinction is that bulbar palsy is a lower motor neurone (LMN) disorder, whereas pseudobulbar palsy is a bilateral upper motor neurone (UMN) corticobulbar disorder.

1. Site of Lesion

Bulbar palsy: The lesion affects the motor cranial nerve nuclei in the medulla or their peripheral nerves, particularly pathways involving cranial nerves IX, X and XII.

Pseudobulbar palsy: The lesion is above the cranial nerve nuclei and affects the corticobulbar tracts bilaterally.

Therefore:

Bulbar = cranial nerve nuclei/nerves → LMN.

Pseudobulbar = bilateral corticobulbar tracts → UMN.

2. Type of Motor Neurone Lesion

Bulbar palsy: Lower motor neurone lesion.

Because LMNs are damaged, the affected muscles become weak and may undergo atrophy and fasciculation.

Pseudobulbar palsy: Upper motor neurone lesion.

Loss of descending cortical control produces spasticity and exaggerated reflexes rather than prominent muscle wasting and fasciculations.

3. Cranial Nerve Functions Affected

Both conditions particularly interfere with functions mediated through:

CN IX – glossopharyngeal nerve.

CN X – vagus nerve.

CN XII – hypoglossal nerve.

However, pseudobulbar palsy is better considered a bilateral corticobulbar syndrome, so facial and jaw movements may also be affected.

4. Tongue in Bulbar Palsy

The tongue in bulbar palsy is characteristically:

Weak.

Wasted or atrophied.

Fasciculating.

Movement of the tongue may be markedly reduced.

The combination of tongue wasting + fasciculations is a classic clue to LMN involvement.

5. Tongue in Pseudobulbar Palsy

The tongue in pseudobulbar palsy is:

Stiff.

Spastic.

Slow-moving.

There are generally no prominent fasciculations because the lower motor neurones themselves remain intact.

Therefore:

Wasted + fasciculating tongue → bulbar palsy.

Spastic tongue without fasciculations → pseudobulbar palsy.

6. Dysarthria

Both disorders can produce dysarthria, but the character of the speech differs.

Bulbar palsy: Speech is flaccid, weak, slurred and often nasal because of weakness of the tongue, palate, pharynx and larynx.

Pseudobulbar palsy: Speech is typically slow, strained and spastic. Older textbooks sometimes describe this as “Donald Duck speech.”

7. Dysphagia

Dysphagia can occur in both conditions.

In bulbar palsy, weakness of the palate, pharynx and larynx can cause:

Choking.

Coughing during meals.

Nasal regurgitation of fluids.

Aspiration.

In pseudobulbar palsy, swallowing is impaired because voluntary control of the swallowing musculature is disrupted by bilateral corticobulbar damage.

Both conditions can therefore cause clinically important aspiration.

8. Nasal Regurgitation

Bulbar palsy: Nasal regurgitation is particularly characteristic because weakness of the soft palate prevents adequate closure of the nasopharynx during swallowing.

Pseudobulbar palsy: Dysphagia occurs, but the classical picture is dominated more by spastic swallowing dysfunction rather than flaccid palatal weakness.

9. Jaw Jerk

The jaw jerk is one of the most useful examination differences.

Bulbar palsy: The jaw jerk is not characteristically exaggerated and may be reduced if the relevant LMN reflex pathway is involved.

Pseudobulbar palsy: The jaw jerk is brisk or exaggerated because of bilateral UMN corticobulbar damage.

Therefore:

Exaggerated jaw jerk → think pseudobulbar palsy.

10. Gag Reflex

Bulbar palsy: The gag reflex may be reduced or absent when the relevant IX/X lower motor pathways are affected.

Pseudobulbar palsy: Bulbar reflexes may be brisk or exaggerated because of loss of descending inhibitory control.

However, the gag reflex naturally varies between individuals, so it should not be interpreted alone.

11. Muscle Wasting

Bulbar palsy: Muscle wasting occurs because the lower motor neurones directly supplying the muscles are damaged.

Pseudobulbar palsy: Marked denervation wasting is not expected because the lower motor neurones remain intact.

This again follows the general rule:

LMN → wasting and fasciculations.

UMN → spasticity and hyperreflexia.

12. Fasciculations

Bulbar palsy: Fasciculations, particularly of the tongue, may be clearly visible.

Pseudobulbar palsy: Fasciculations are generally absent.

A wasted fasciculating tongue should therefore immediately suggest a lower motor neurone bulbar lesion.

13. Emotional Lability

Bulbar palsy: Emotional lability is not a characteristic consequence of the LMN lesion itself.

Pseudobulbar palsy: Emotional lability is characteristic.

The patient may have sudden episodes of uncontrollable:

Laughing.

or

Crying.

This is known as pseudobulbar affect.

14. Causes of Bulbar Palsy

Important causes include:

Motor neurone disease.

Guillain–Barré syndrome.

Other diseases affecting the medullary motor nuclei or lower cranial nerves can also produce bulbar weakness.

Motor neurone disease is particularly important because it may produce both LMN and UMN abnormalities.

15. Causes of Pseudobulbar Palsy

Important causes include:

Bilateral cerebrovascular disease, such as multiple strokes affecting the corticobulbar pathways.

Multiple sclerosis.

Motor neurone disease.

Other disorders producing bilateral corticobulbar tract damage can also cause the syndrome.

16. Motor Neurone Disease Can Cause Both

An important point is that motor neurone disease can produce both bulbar and pseudobulbar features.

This occurs because diseases such as ALS can damage both:

LMNs → bulbar palsy.

and

UMNs → pseudobulbar palsy.

Therefore, a patient with motor neurone disease may have mixed findings.

For example:

Tongue fasciculations → LMN involvement.

Brisk jaw jerk → UMN involvement.

Finding both suggests combined upper and lower motor neurone disease.

17. Bulbar Palsy – Quick Note Form

Lesion: LMN.

Site: cranial nerve nuclei/peripheral lower cranial nerves.

Important nerves: IX, X, XII.

Tongue: wasted, weak and fasciculating.

Speech: weak, flaccid and often nasal.

Swallowing: dysphagia.

Nasal regurgitation: common with palatal weakness.

Jaw jerk: not exaggerated.

Gag: may be reduced.

Emotional lability: not characteristic.

Main causes: motor neurone disease and Guillain–Barré syndrome.

18. Pseudobulbar Palsy – Quick Note Form

Lesion: UMN.

Site: bilateral corticobulbar tracts.

Tongue: stiff/spastic without prominent fasciculations.

Speech: slow, strained and spastic.

Swallowing: dysphagia.

Jaw jerk: exaggerated/brisk.

Bulbar reflexes: may be exaggerated.

Emotional lability: characteristic.

Main causes: bilateral cerebrovascular disease, multiple sclerosis and motor neurone disease.

19. Fastest Examination Distinction

When trying to distinguish the two at the bedside, look particularly at the tongue, jaw jerk and emotional response.

Bulbar palsy:

Wasted fasciculating tongue

↓

LMN

↓

Weak/flaccid speech + dysphagia

Pseudobulbar palsy:

Spastic tongue + brisk jaw jerk + emotional lability

↓

Bilateral UMN corticobulbar lesion

↓

Spastic speech + dysphagia

Key Clinical Differences

Bulbar palsy = LMN.

Pseudobulbar palsy = bilateral UMN.

Bulbar → tongue wasted and fasciculating.

Pseudobulbar → tongue spastic, no prominent fasciculations.

Bulbar → flaccid/nasal dysarthria.

Pseudobulbar → spastic/strained dysarthria.

Bulbar → jaw jerk not exaggerated.

Pseudobulbar → jaw jerk exaggerated.

Bulbar → gag may be reduced.

Pseudobulbar → reflexes may be brisk.

Bulbar → emotional lability not characteristic.

Pseudobulbar → emotional lability characteristic.

Bulbar causes → MND + Guillain–Barré syndrome.

Pseudobulbar causes → bilateral strokes + MS + MND.

Key Clinical Pattern

The easiest memory rule is:

BULBAR = LMN = WASTING

PSEUDOBULBAR = UMN = SPASTICITY

So:

Wasted fasciculating tongue → Bulbar palsy.

Spastic tongue + brisk jaw jerk + emotional lability → Pseudobulbar palsy.

Medicine – Bulbar Palsy

Bulbar palsy is a lower motor neurone (LMN) syndrome caused by dysfunction of the motor cranial nerve nuclei in the medulla or their peripheral nerves. It primarily affects the muscles responsible for speech, swallowing, chewing, and tongue movement.

The most important cranial nerves involved are IX (glossopharyngeal), X (vagus), and XII (hypoglossal), although other lower cranial nerves may also be involved depending on the underlying disease.

1. Anatomical Basis

The term “bulbar” refers to the medulla oblongata, historically called the bulb.

The medulla contains important motor nuclei controlling the pharynx, larynx, and tongue. Damage to these nuclei or their peripheral axons produces lower motor neurone weakness of the bulbar muscles.

Therefore:

Cranial nerve nuclei/peripheral nerves damaged → LMN bulbar weakness → bulbar palsy.

2. Cranial Nerves Involved

The major cranial nerves involved are:

CN IX – glossopharyngeal nerve: contributes to pharyngeal sensation and swallowing.

CN X – vagus nerve: controls much of the palate, pharynx, and larynx.

CN XII – hypoglossal nerve: controls tongue movements.

In some disorders, CN XI and other cranial motor functions may also be affected.

3. Lower Motor Neurone Disorder

Bulbar palsy is fundamentally a lower motor neurone disorder.

This distinguishes it from pseudobulbar palsy, which results from bilateral upper motor neurone lesions affecting the corticobulbar pathways.

The LMN nature of bulbar palsy explains the characteristic:

Muscle weakness.

Muscle wasting.

Fasciculations.

Reduced reflex activity where the relevant reflex arc is affected.

4. Tongue Atrophy

Damage to the hypoglossal lower motor neurones causes weakness and atrophy of the tongue.

The tongue may appear:

Thin.

Wasted.

Wrinkled or furrowed.

Tongue movements become weak and poorly coordinated.

5. Tongue Fasciculations

Fasciculations are another characteristic LMN finding.

These are small, spontaneous contractions of individual motor units that may be visible beneath the surface of the tongue.

Therefore:

Wasted + fasciculating tongue → think LMN lesion → bulbar palsy.

This is particularly important when motor neurone disease is suspected.

6. Pharyngeal Weakness

Weakness of the pharyngeal muscles interferes with the normal swallowing mechanism.

Food or fluid may not be effectively propelled from the mouth and pharynx into the oesophagus.

This produces dysphagia and increases the risk of aspiration.

7. Laryngeal Weakness

Weakness of muscles supplied through the vagus nerve can impair laryngeal function.

The patient’s voice may become:

Weak.

Hoarse.

Breathy.

Speech may become increasingly difficult to understand.

Laryngeal weakness also reduces the patient’s ability to protect the airway effectively during swallowing.

8. Palatal Weakness

Weakness of the soft palate may result in poor closure of the nasopharynx during speech and swallowing.

This can produce:

Nasal speech.

Nasal regurgitation of liquids.

On examination, palatal movement may be reduced.

9. Dysarthria

Dysarthria is common because weakness affects the tongue, palate, pharynx, and larynx.

Speech in bulbar palsy is typically weak and flaccid, and it may have a nasal quality.

This contrasts with the strained, spastic dysarthria of pseudobulbar palsy.

10. Dysphagia

Dysphagia is one of the most clinically important manifestations.

Patients may have difficulty swallowing both food and liquids.

They may experience:

Choking during meals.

Coughing after swallowing.

Food sticking in the throat.

Nasal regurgitation of fluids.

Recurrent aspiration.

11. Nasal Regurgitation

Nasal regurgitation occurs because weakness of the soft palate prevents effective closure between the oropharynx and nasopharynx during swallowing.

As a result, particularly with liquids:

Swallowed fluid → enters nasopharynx → comes out through the nose.

This is a useful clinical clue to bulbar muscle weakness.

12. Aspiration

Failure of effective pharyngeal and laryngeal function can allow food, fluid, or saliva to enter the airway.

This may cause:

Choking episodes.

Aspiration pneumonia.

Recurrent chest infections.

Aspiration is one of the major complications of severe bulbar palsy.

13. Gag Reflex

The gag reflex may be reduced or absent when the relevant lower motor neurone pathways involving cranial nerves IX and X are damaged.

However, the gag reflex is naturally variable between individuals and should not be interpreted in isolation.

The overall pattern of bulbar weakness is more important.

14. Motor Neurone Disease

Motor neurone disease (MND) is an important cause of progressive bulbar palsy.

In amyotrophic lateral sclerosis, degeneration may affect both upper and lower motor neurones.

Bulbar LMN involvement can produce:

Tongue wasting.

Tongue fasciculations.

Dysarthria.

Dysphagia.

Weak cough.

15. Progressive Bulbar Palsy

Some patients with motor neurone disease initially present predominantly with progressive weakness of the bulbar muscles.

This clinical presentation has traditionally been called progressive bulbar palsy.

Over time, signs of motor neurone disease may become apparent elsewhere in the body.

16. Mixed Bulbar and Pseudobulbar Features in MND

Motor neurone disease can affect both:

Lower motor neurones → bulbar signs.

and

Upper motor neurones → pseudobulbar signs.

A patient may therefore demonstrate a mixture, such as tongue fasciculations together with a brisk jaw jerk.

This mixed UMN/LMN pattern is particularly important in ALS.

17. Guillain–Barré Syndrome

Guillain–Barré syndrome (GBS) can also cause bulbar palsy through involvement of peripheral cranial nerves.

Patients may develop:

Facial weakness.

Dysphagia.

Dysarthria.

Impaired airway protection.

Bulbar involvement is clinically important because it can accompany respiratory muscle weakness.

18. Respiratory Risk in Guillain–Barré Syndrome

A patient with GBS and bulbar weakness requires careful respiratory assessment.

Weakness of respiratory and bulbar muscles can lead to:

Aspiration.

Ineffective cough.

Retention of secretions.

Respiratory failure.

Severe cases require close monitoring and sometimes mechanical ventilation.

19. Other Causes of Bulbar Palsy

Although your notes emphasise MND and GBS, other lesions affecting the lower cranial nerve nuclei or nerves can produce a bulbar syndrome.

Examples include:

Brainstem infarction.

Brainstem tumours.

Poliomyelitis in relevant settings.

Other peripheral neuropathies affecting lower cranial nerves.

The exact pattern depends on the anatomical site involved.

20. Bulbar Palsy versus Pseudobulbar Palsy – Note Form

Bulbar palsy: lower motor neurone lesion.

Pseudobulbar palsy: bilateral upper motor neurone corticobulbar lesion.

Bulbar tongue: wasted and fasciculating.

Pseudobulbar tongue: stiff/spastic without prominent fasciculations.

Bulbar speech: weak, flaccid and often nasal.

Pseudobulbar speech: slow, strained and spastic.

Bulbar jaw jerk: usually not exaggerated.

Pseudobulbar jaw jerk: characteristically brisk/exaggerated.

Bulbar gag reflex: may be reduced or absent.

Pseudobulbar reflexes: may be exaggerated.

Bulbar emotional lability: not characteristic.

Pseudobulbar emotional lability: characteristic pseudobulbar affect may occur.

Bulbar main pathology: cranial nerve nuclei or peripheral lower cranial nerves.

Pseudobulbar main pathology: bilateral corticobulbar tracts.

21. Investigation

Investigation depends on the suspected underlying cause.

Possible investigations include:

MRI of the brain and brainstem when a structural lesion is suspected.

Nerve-conduction studies and EMG when motor neurone disease or peripheral neuropathy is considered.

CSF examination when an inflammatory neuropathy such as GBS is suspected.

In GBS, CSF classically demonstrates:

Raised protein + relatively few cells = albuminocytologic dissociation.

22. Management

Treatment is directed toward the underlying disorder, but supportive management of bulbar dysfunction is crucial.

This may involve:

Speech and language therapy.

Formal swallowing assessment.

Dietary modification.

Aspiration precautions.

Nutritional support.

Respiratory monitoring.

Severe dysphagia may eventually require enteral feeding, depending on the underlying condition and clinical circumstances.

23. Bulbar Palsy – Note Form

Type: lower motor neurone syndrome.

Main cranial nerves: IX, X and XII.

Tongue: atrophied, weak and fasciculating.

Pharynx: weak → dysphagia and choking.

Palate: weak → nasal speech and nasal regurgitation of liquids.

Larynx: weak → dysphonia/hoarse or weak voice and impaired airway protection.

Speech: flaccid dysarthria.

Swallowing: dysphagia with aspiration risk.

Reflexes: gag may be reduced; jaw jerk is not characteristically exaggerated.

Major cause: motor neurone disease.

Another important cause: Guillain–Barré syndrome.

Key Clinical Pattern

Remember bulbar palsy as:

LMN lesion of lower cranial motor pathways → dysarthria + dysphagia + nasal regurgitation + wasted fasciculating tongue.

The easiest distinction is:

Bulbar palsy = LMN → wasted fasciculating tongue + weak/flaccid speech.

Pseudobulbar palsy = UMN → spastic tongue + brisk jaw jerk + emotional lability.

For the causes in your notes, remember:

Motor neurone disease + Guillain–Barré syndrome → bulbar palsy.

Medicine – Pseudobulbar Palsy

Pseudobulbar palsy is an upper motor neurone (UMN) syndrome caused by bilateral damage to the corticobulbar pathways that control the muscles of speech, swallowing, chewing, and facial expression.

It resembles bulbar palsy clinically, but the underlying lesion is different. In pseudobulbar palsy the problem is supranuclear and bilateral, whereas true bulbar palsy results from lower motor neurone damage involving the cranial nerve nuclei or their peripheral nerves.

1. Anatomical Basis

The motor nuclei of the cranial nerves receive descending input from the motor cortex through the corticobulbar tracts.

Pseudobulbar palsy occurs when these corticobulbar pathways are damaged bilaterally.

The clinically important functions particularly involve pathways controlling cranial nerves:

IX – glossopharyngeal nerve.

X – vagus nerve.

XII – hypoglossal nerve.

However, pseudobulbar palsy is better understood as a bilateral corticobulbar syndrome rather than simply impairment of cranial nerves IX, X and XII, because facial and jaw movements can also be affected.

2. Why the Lesion Must Usually Be Bilateral

Most cranial motor nuclei receive substantial corticobulbar input from both cerebral hemispheres.

Consequently, a unilateral corticobulbar lesion often does not produce the full syndrome.

Significant pseudobulbar palsy usually develops after bilateral corticobulbar tract damage.

Therefore:

Bilateral UMN corticobulbar lesions → pseudobulbar palsy.

3. Dysarthria

Dysarthria is a prominent feature.

Because the muscles controlling speech are spastic and poorly coordinated, speech becomes:

Slow.

Strained.

Harsh.

Indistinct.

Older textbooks sometimes describe this as “Donald Duck speech.” This is a historical descriptive term; spastic dysarthria is the more useful clinical terminology.

4. Dysphagia

Difficulty swallowing, or dysphagia, is another important manifestation.

Patients may have difficulty coordinating the pharyngeal and laryngeal muscles required for safe swallowing.

This can lead to:

Choking.

Coughing during meals.

Aspiration.

Recurrent aspiration pneumonia.

Therefore, swallowing assessment is important in clinically significant pseudobulbar palsy.

5. Tongue Appearance

The tongue may appear small, stiff, and spastic, with impaired voluntary movement.

Because this is an upper motor neurone lesion, there is generally no prominent fasciculation.

This is an important distinction from true bulbar palsy.

6. Tongue in Pseudobulbar versus Bulbar Palsy

In pseudobulbar palsy:

Tongue → spastic and slow-moving, without prominent fasciculations.

In bulbar palsy:

Tongue → wasted, weak and may show fasciculations.

This distinction reflects the difference between UMN and LMN pathology.

7. Exaggerated Jaw Jerk

The jaw jerk is exaggerated or brisk in pseudobulbar palsy.

This occurs because bilateral corticobulbar damage removes normal descending inhibition of the trigeminal motor reflex pathway.

Therefore:

Brisk jaw jerk → UMN corticobulbar lesion → supports pseudobulbar palsy.

8. Other Exaggerated Reflexes

Other bulbar reflexes may also become exaggerated.

Patients may demonstrate:

Brisk gag reflex.

Exaggerated facial reflexes.

Pathological emotional responses.

These findings reflect loss of supranuclear inhibitory control.

9. Emotional Lability

A characteristic feature is emotional lability, also called pseudobulbar affect.

Patients may experience sudden, involuntary episodes of:

Crying.

Laughing.

These responses may be exaggerated, difficult to control, or inappropriate to the emotional context.

10. Pseudobulbar Affect

Pseudobulbar affect does not necessarily mean that the patient is genuinely feeling extremely sad or happy.

Instead, damage to neural pathways regulating emotional expression produces a mismatch between the patient’s internal emotional state and outward expression.

Thus:

Uncontrollable laughing or crying + bilateral corticobulbar disease → pseudobulbar affect.

11. Bilateral Cerebrovascular Disease

One of the classic causes of pseudobulbar palsy is bilateral cerebrovascular disease affecting the corticobulbar pathways.

The original note describes bilateral internal-capsule lesions as the most common cause.

Multiple strokes involving the internal capsules or other corticobulbar pathways can indeed produce the syndrome.

A single unilateral internal-capsule stroke usually does not produce the complete classical pseudobulbar syndrome.

12. Multiple Sclerosis

Multiple sclerosis can cause pseudobulbar palsy when demyelinating lesions affect corticobulbar pathways on both sides.

Other neurological findings suggesting MS may coexist, including:

Optic neuritis.

Upper motor neurone limb weakness.

Sensory abnormalities.

Internuclear ophthalmoplegia.

Ataxia.

Bladder dysfunction.

13. Motor Neurone Disease

Motor neurone disease, particularly amyotrophic lateral sclerosis, may involve corticobulbar upper motor neurone pathways.

Patients can therefore develop pseudobulbar features such as:

Spastic dysarthria.

Brisk jaw jerk.

Emotional lability.

However, motor neurone disease may involve both upper and lower motor neurones, so patients can develop a mixture of pseudobulbar and true bulbar signs.

14. Other Causes

Other bilateral cerebral disorders can also produce pseudobulbar palsy.

These include:

Traumatic brain injury.

Certain neurodegenerative diseases.

Bilateral cerebral tumours or structural lesions.

Other disorders producing bilateral corticobulbar tract damage.

The underlying principle is always the same:

Bilateral corticobulbar UMN damage → pseudobulbar palsy.

15. Bulbar Palsy

Bulbar palsy, by contrast, is a lower motor neurone syndrome involving the motor nuclei of the medulla or the corresponding cranial nerves.

It particularly affects cranial nerves IX, X, XI and XII, depending on the underlying disorder.

Patients develop dysarthria and dysphagia, just as in pseudobulbar palsy, but the examination findings are different.

16. Pseudobulbar Palsy versus Bulbar Palsy – Note Form

Pseudobulbar palsy: upper motor neurone disorder.

Bulbar palsy: lower motor neurone disorder.

Pseudobulbar lesion: bilateral corticobulbar tracts.

Bulbar lesion: cranial nerve nuclei or peripheral cranial nerves.

Pseudobulbar tongue: stiff/spastic, without prominent fasciculations.

Bulbar tongue: weak, wasted and fasciculating.

Pseudobulbar jaw jerk: brisk or exaggerated.

Bulbar jaw jerk: usually reduced or absent when the relevant LMN reflex arc is affected.

Pseudobulbar emotional lability: characteristic.

Bulbar emotional lability: not a characteristic LMN feature.

Pseudobulbar speech: spastic, strained dysarthria.

Bulbar speech: flaccid, weak dysarthria, often nasal depending on the muscles involved.

17. Clinical Assessment

Evaluation should determine the underlying cause of the bilateral corticobulbar dysfunction.

Depending on the presentation, investigations may include:

MRI or CT of the brain.

Assessment for previous or acute cerebrovascular disease.

MRI for demyelinating disease.

Neuromuscular assessment if motor neurone disease is suspected.

Swallowing and speech assessments are also important because aspiration and communication difficulties can significantly affect patients.

18. Management

Treatment is directed primarily toward the underlying neurological disease.

Supportive management may include:

Speech and language therapy.

Swallowing assessment.

Dietary modification.

Aspiration prevention.

Nutritional support when required.

Treatment of pseudobulbar affect when troublesome.

19. Pseudobulbar Palsy – Note Form

Type of lesion: upper motor neurone.

Anatomical lesion: bilateral corticobulbar pathways.

Important cranial functions affected: particularly those mediated through IX, X and XII, with additional facial and jaw involvement possible.

Speech: spastic dysarthria; historically described as “Donald Duck speech.”

Swallowing: dysphagia with aspiration risk.

Tongue: small/stiff and spastic, without the marked wasting and fasciculation of LMN bulbar palsy.

Jaw jerk: exaggerated.

Emotional feature: emotional lability or pseudobulbar affect with inappropriate/uncontrollable laughing or crying.

Cerebrovascular cause: bilateral corticobulbar damage from multiple strokes, including bilateral internal-capsule lesions.

Demyelinating cause: multiple sclerosis.

Motor neurone cause: motor neurone disease/ALS, which may produce mixed UMN and LMN bulbar findings.

Key Clinical Pattern

Remember pseudobulbar palsy as:

Bilateral corticobulbar UMN lesion → dysarthria + dysphagia + spastic tongue + brisk jaw jerk + emotional lability.

The easiest distinction is:

Pseudobulbar palsy = UMN → brisk jaw jerk + spastic tongue + emotional lability.

Bulbar palsy = LMN → wasted fasciculating tongue + reduced LMN reflexes.

And the major causes to remember are:

Bilateral cerebrovascular disease + multiple sclerosis + motor neurone disease.