Sixth cranial nerve palsy

Published on 02/04/2015 by admin

Filed under Internal Medicine

Last modified 22/04/2025

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52 Sixth cranial nerve palsy

Instruction

Examine this patient’s eyes.

Salient features

History

• Diplopia in all directions of gaze except away from the affected side

• Patient may rotate the head towards the weak side to produce a single image

• Patient may intentionally close the affected eye to prevent diplopia (pseudo ptosis)

• Hearing loss (acoustic neuroma)

• Diabetes or hypertension.

Examination

• The eye is deviated medially and there is failure of lateral movement.

• The diplopia is maximal when looking towards the affected side. The two images are parallel and separated in the horizontal plane. The outer image comes from the affected eye and disappears when the eye is covered.

• Proceed by telling the examiner that you would like to check the following:

• Blood pressure and urine sugar
• Hearing and corneal sensation (early signs of acoustic neuroma).

Diagnosis

This patient has a sixth nerve palsy (lesion) caused by diabetes mellitus (aetiology) and is having severe diplopia (functional status).

Questions

What are the causes of sixth nerve palsy?

• Hypertension

• Diabetes

• Raised intracranial pressure (false localizing signs)

• Multiple sclerosis

• Basal meningitis

• Encephalitis

• Acoustic neuroma, nasopharyngeal carcinoma

• Lyme disease (N Engl J Med 2007;356:1561).

Advanced-level questions

Where is the nucleus of the sixth nerve located?

In the pons. (The nuclei of the first four cranial nerves are situated above the pons and those of the last four cranial nerves are situated below the pons.)

What are the structures in close proximity to the sixth nerve nucleus and fascicles?

These include:

• facial and trigeminal nerves

• corticospinal tract

• median longitudinal fasciculus

• parapontine reticular formation.

A combination of clinical findings pointing to the involvement of these structures indicates the presence of an intrapontine lesion.

What you know about the peripheral course of the abducens nerve?

It is lengthy: from the brainstem and base of the skull through the petrous tip and cavernous sinus to the superior orbital fissure and orbit. Lesions at any of these sites may affect the nerve.

Have you heard of Gradenigo syndrome?

Inflammation of the tip of the temporal bone may involve the fifth and sixth cranial nerves as well as the greater superficial petrosal nerve, resulting in unilateral paralysis of the lateral rectus nerve, pain in the distribution of the trigeminal nerve (particularly its first division) and excessive lacrimation.

Do you know any eponymous syndromes where the pons is infarcted and consequently the sixth cranial nerve is involved?

• Raymond syndrome: ipsilateral sixth nerve paralysis and contralateral paresis of the extremities

• Millard–Gubler syndrome, in which there is ipsilateral sixth and seventh nerve palsy with contralateral hemiplegia

• Foville syndrome has all the features of Millard–Gubler paralysis with lateral conjugate gaze palsy.

Mention other syndromes with sixth nerve involvement

• Duane syndrome: widening of the palpebral fissure on abduction and narrowing on adduction

• Gerhardt syndrome: bilateral abducens palsy

• Möbius syndrome: paralysis of extraocular muscles, especially abducens, with paresis of facial muscles.

What do you know about Tolosa–Hunt syndrome?

It is a syndrome characterized by unilateral recurrent pain in the retro-orbital region with palsy of the extraocular muscles resulting from involvement of the third, fourth, fifth and sixth cranial nerves. It has been attributed to inflammation of the cavernous sinus.

C Gradenigo (1859–1926), an Italian otolaryngologist, described this syndrome in 1904.

E Tolosa, a Spanish neurosurgeon.

WE Hunt, an American neurosurgeon.

ALJ Millard (1830–1915), a French physician.

AM Gubler (1821–1915), Professor of Therapeutics in France.

ALF Foville (1799–1878), Professor of Physiology at Rouen, described his syndrome in 1848.

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