Internuclear and Supranuclear Disorders of Eye Movement

Eye movements let us fixate on and follow a moving visual target. These movements are performed by the ocular motor system that
is divided according to anatomic location into infranuclear, nuclear, internuclear, and supranuclear components. It is important to
distinguish supranuclear and internuclear from nuclear and infranuclear disturbances. Internuclear ophthalmoplegia is due to a lesion of the medial longitudinal fasciculus, caused by multiple sclerosis in younger patients, particularly when the ophthalmoplegia is
bilateral, and usually of vascular origin in the elderly. Supranuclear disorders of eye movements are characterized by gaze palsies, tonic gaze deviation, saccadic and smooth pursuit disorders, vergence abnormalities, nystagmus, and ocular oscillations. Supranuclear
disorders result from lesions above the level of the ocular motor nerve nuclei, and they account for almost 10% of all patients with
disorders of eye movements. If oculocephalic maneuvers move the eyes appropriately, the lesion causing the gaze palsy is supranuc-
lear; if oculocephalic maneuvers do not move the eyes, the lesion may be internuclear, nuclear, or infranuclear.