Quantitative Analysis of the Visual Vestibulo-Ocular Reflex Induced by Sinusoidal Rotation in Patients with Peripheral Vestibular Disorders

In order to investigate the interaction between the vestibular and optokinetic systems in patients with peripheral vestibular disorders, the visual vestibulo-ocular reflex (V-VOR) gain in thirty-seven patients with peripheral vestibular disorders was measured using pen-dular harmonic sinusoidal rotation with optokinetic stationary stimuli. The patients were rotated sinusoidally at an amplitude of 240° and at a frequency of 0.1 Hz (maximum velocity 75.4°s), both with eyes closed and open. Comparing the vestibulo-ocular reflex (VOR) and V-VOR gains in the patients with definite Meniere's disease (17 cases), benign paroxismal positional vertigo (BPPV, 10 cases) and sudden deafness with vertigo or dizziness (10 cases), VOR-DP and a normal V-VOR gain were more frequently observed in patients with Meniere's disease (17 cases) and sudden deafness (7 cases) than in those with the BPPV (3 cases). In two patients with bilateral Meniere's disease, an abnormally decreased VOR-gain (under 0.5) in the bilateral directions with normal V-VOR gain was measured when tested independently. However, an abnormal V-VOR gain was observed in only one patient of sudden deafness due to a retro-cochlear lesion. From our VOR and V-VOR gain observation and that of caloric responses, we have concluded that VOR and V-VOR gains provided additional information for the evaluation of peripheral vestibular disorders as well as central nervous system disorders.