Internuclear Ophthalmoplegia

When a person looks to the side opposite the affected (right) eye, the following happens:

• The affected (right) eye, which should turn inward, cannot move past the midline. That is, the affected eye looks straight ahead.
• As the other eye (left) turns outward, it often makes involuntary, repetitive fluttering movements called nystagmus That is, the eye rapidly moves in one direction, then slowly drifts in the other direction.
• May have double vision.

Internuclear ophthalmoplegia (INO) is a manifestation of intrinsic brainstem disease.

It is caused by a lesion involving the medial longitudinal fasciculus between the abducens and oculomotor nuclei.

Typically INO results from conditions which produce ischemia or demyelination in the brainstem.

The chief clinical features are an adduction deficit in the eye on the side of the lesion and nystagmus in the contralateral eye on attempted lateral gaze.

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Internuclear ophthalmoplegia is impairment of horizontal eye movements caused by damage to certain connections between nerve centers in the brain stem.

In internuclear ophthalmoplegia, the nerve fibers that coordinate both eyes in horizontal movements—looking from side to side—are damaged. These fibers connect collections of nerve cells (centers or nuclei) that the 3rd cranial nerve (oculomotor nerve) and the 6th cranial nerve (abducens nerve) originate from.

In older people, the disorder usually results from a stroke, and only one eye is affected.

In younger people, it usually results from multiple sclerosis, and both eyes are often affected.

Less common causes include Lyme disease, tumors, and toxicity due to a drug (such as tricyclic antidepressants).

Horizontal eye movements are impaired, but vertical ones are not.

The affected eye cannot turn inward, but it can turn outward.

http://www.merck.com/mmhe/sec06/ch096/ch096b.html

Thanks to Dr Ngiu for showing us the patient with RIGHT INTERNUCLEAR OPHTHALMOPLEGIA today. We really appreciate the findings as mentioned above.

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