Eye movements are examined by having the patient look to the right and to the left and up and down. Two abnormalities may be seen that typify MS. One is nystagmus, the involuntary jerking of the eyes as they gaze in different directions or sometimes even at rest. The second is weakness of the eyes, more of one eye than the other, in looking to one side. This asymmetrical gaze weakness is called internuclear ophthalmoplegia. Internuclear ophthalmoplegia indicates a brain stem lesion. Nystagmus points to either the brain stem or cerebellum or their connections to the inner ear.
Two rare signs, which also reveal MS involvement of the brain stem, are third-nerve palsy and Horner's syndrome, both of which show an eyelid droop on one side. In third-nerve palsy, there is also dilation of the pupil and weakness of all eye movements except looking outward. In Horner's syndrome, there is constriction of the pupil and no gaze weakness.

More About this Book
Multiple Sclerosis
Continue Learning about Multiple Sclerosis Treatment
Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.