Short vestibulo-ocular reflex time-constant in complete unilateral vestibular lesions

The time-constant of the vestibulo-ocular reflex (VORtc) in response to short accelerations was studied in 18 patients with complete unilateral vestibular lesions: 12 patients with incomplete lesions and 9 healthy controls. The marked group differences in VORtc, which was short in patients with complete lesions and long (i.e., > or = 10 s) in the controls and some patients with incomplete lesions, suggests the finding of a long VORtc in a patient with a unilateral vestibular lesion to indicate the presence of an incomplete lesion. Moreover, one analytic method (where the initial phase of decay is weighted) showed the VORtc to be longer following stimulation toward the healthy ear than following stimulation toward the lesioned ear, whereas other analytic methods showed no direction asymmetry in VORtc.