Visual-vestibular interaction in multiple sclerosis.

Visual modulation of the vestibuloocular reflex (VOR) was analyzed in 20 patients with multiple sclerosis who had no vestibular or ocular motor symptoms. Visual suppression of the VOR was impaired in 75% of patients. VOR gains in darkness were elevated in 35% of patients. Elevated VOR gain in darkness is attributed to vestibular adaptation to defective smooth pursuit. This vestibular plasticity achieved retinal image stability by matching eye velocity to head velocity when stationary targets were viewed. The high incidence of impaired visual suppression of the VOR rivals the sensitivity of other physiologic tests used to identify multiple sclerosis.