Internuclear ophthalmoplegia

81 Internuclear ophthalmoplegia



Instruction


Examine this patient’s eyes.



Salient features



History




• Diplopia


• 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.


image

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.

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Dec 4, 2016 | Posted by in GENERAL & FAMILY MEDICINE | Comments Off on Internuclear ophthalmoplegia

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