Subclinical eye movement disorders in patients with multiple sclerosis.

Eye movements were quantitatively evaluated in 16 patients with well-documented multiple sclerosis who had minimal or no clinically apparent eye movement disorder. Induced saccade and pursuit eye movements were recorded with electro-oculography and analyzed with newly developed programs on a laboratory digital computer. Thirteen of the 16 patients had significant (p less than 0.05) impairment of saccades and/or smooth pursuit when compared with 25 normal subjects tested in our laboratory. The type and frequency of abnormalities were as follows: saccade dysmetria, eight; delayed saccade reaction time, five; bilateral saccade slowing, four; slowing of adducting saccades only (medial longitudinal fasciculus syndrome), one; and impaired smooth pursuit, both directions, three, and one direction only, three. In addition, four patients had vestibular nystagmus with eyes closed, and one patient had typical rebound nystagmus. These data suggest that quantitative assessment of eye movements in patients with suspected multiple sclerosis can help in identifying the important "second lesion."