Internuclear ophthalmoplegia

Published on 05/05/2015 by admin

Filed under Internal Medicine

Last modified 22/04/2025

Print this page

This article have been viewed 1620 times

[level-membership-for-internal-medicine-category]

81 Internuclear ophthalmoplegia

Instruction

Examine this patient’s eyes.

Salient features

History

• History of multiple sclerosis

• Neurofibroma (causing pontine gliomas)

• Drugs (phenytoin, carbamezapine).

Examination

• Nystagmus is more prominent in the abducting eye (Harris’ sign)

• Diverging squint

• Abduction in either eye is normal, whereas adduction is impaired (Fig. 81.1): there is dissociation of eye movements. On covering the abducting eye, the adduction in the other eye is normal.

Fig. 81.1 Internuclear ophthalmoplegia. (A) Gaze straight ahead. (B) Attempted right gaze, the right abducting eye achieves the target earlier than the left adducting eye. The vertical line indicates the midpupillary point; the left pupil does not move off this when the gaze changes.

Proceed as follows:

• Tell the examiner that you would like to look for other signs of demyelination: optic atrophy, pale discs, pyramidal signs.

Remember: Multiple sclerosis and microvascular brainstem ischaemia are the most common causes of internuclear ophthalmoplegia. The two causes may be distinguished by age at presentation, with younger patients likely to have demyelination and older patients ischaemia.

Diagnosis

This patient has internuclear ophthalmoplegia (lesion), which is probably caused by multiple sclerosis (aetiology).

Advanced-level questions

Where is the lesion?

In the medial longitudinal bundle, which connects the sixth nerve nucleus on one side to the third nerve nucleus on the opposite side of the brainstem. The eye will not adduct because the third nerve and, therefore, the medial rectus have been disconnected from the lateral gaze centre and sixth nucleus of the opposite side.

What are the causes?

• Multiple sclerosis

• Vascular disease

• Tumour (pontine glioma)

• Inflammatory lesions of the brainstem

• Drugs (phenytoin, carbamezapine)

How would you investigate?

• Edrophonium (Tensilon) test to exclude myasthenia (see Fig. 66.2).

What are the mechanisms to elicit conjugate gaze?

There are four mechanisms for eliciting conjugate gaze in any direction.

• The saccadic system involves voluntary gaze (even when the eyes are shut). Pathways mediating saccadic gaze arise in the frontal lobe and pass to the pontine gaze centre.

• The pursuit system allows the subject to follow a moving object. Pathways mediating pursuit movements arise in the parieto-occipital lobe and pass to the pontine gaze centre.

• The optokinetic system involves the restoration of gaze despite movements from the outside world (e.g. while a subject is sitting in a railway train and looking out of the window, the eyes move slowly as the train moves, to be followed by rapid corrective movement back to the initial position of gaze). This is tested with a hand-held drum bearing vertical black and white stripes. Optokinetic nystagmus is often disturbed even before damage to the pursuit system is apparent.

• The vestibulo-ocular system involves correction of gaze for movements of the head. This is achieved by inputs from the labyrinths and neck proprioreceptors to the brainstem. The patient is asked to fixate to the examiner’s face and the head is briskly rotated by the examiner from side to side or up and down (doll’s head manoeuvre). In supranuclear gaze palsy, these vestibulo-ocular reflex eye movements are preserved, despite the absence of both saccadic and pursuit movements. Caloric tests are used to demonstrate the vestibulo-ocular reflex.

Notes

1 Diplopia is not a feature of defects in conjugate gaze.

2 The centres for saccadic and pursuit movements in the cerebral hemispheres control deviation of the eyes towards the opposite side of the body. These pathways descend towards the brainstem and cross before they reach the pons.

3 The centres for conjugate vertical gaze lie in the midbrain.

4 The centres for conjugate downward vertical gaze are not well localized and lesions both in the midbrain and at the level of the foramen magnum can cause defects of voluntary downgaze.

What do you know about ‘Fisher’s one and a half syndrome’?

It is a syndrome in which horizontal eye movement is absent and the other eye is capable only of abduction—one and a half movements are paralysed. The vertical eye movements and the pupils are normal. The cause is a lesion in the pontine region involving the medial longitudinal fasciculus and the parapontine reticular formation on the same side. This results in failure of conjugate gaze to the same side, impairment of adduction of the eye and nystagmus on abduction of the other eye. One and a half syndrome is most often caused by multiple sclerosis, brainstem stroke, brainstem tumours and arteriovenous malformations.

Internuclear ophthalmoplegia was first reported by Bielschowsky (1902) and then subsequently by Lhermitte in 1922.

Spiller in 1924 described the necropsy findings, implicated the median longitudinal fasciculus and suggested the name ‘ophthalmoplegia internuclearis anterior’.

[/level-membership-for-internal-medicine-category][not-level-membership-for-internal-medicine-category]<

Buy Membership for Internal Medicine Category to continue reading. Learn more here

[/not-level-membership-for-internal-medicine-category]

250 Cases in Clinical Medicine