Headshake versus whole-body rotation testing of the vestibulo-ocular reflex

The vestibulo-ocular reflex (VOR) is usually evaluated by whole-body rotary chair oscillation in darkness, but is limited to ambulatory patients. In order to develop a portable method of VOR assessment, eye movements from 10 normal subjects were studied under three conditions: 1. whole-body rotary chair oscillation in the dark and in the light with a head mounted blank field, 2. passive head-on-body rotation in the light with a blank field, and 3. active head-on-body rotation in the light with a blank field. The influence of visual fixation, neck rotation, and volition on VOR gain was to be assessed. Head oscillations were maintained at 0.5 and 1.0 Hz, 50 degrees/s peak velocity. Mean VOR gains with blank field testing were indistinguishable from those obtained in darkness during whole-body rotation. In addition, there were no significant differences in the mean gain between whole-body, passive head rotation or active head rotation. Two vestibulopathic patients (absent calorics bilaterally and oscillopsia) were also studied to illustrate potential clinical utility of the methods. Rotations under all conditions revealed low but variable gains. The evaluation of the VOR in the light with a blank visual surround and passive or active head rotation is a potentially useful clinical method of bedside assessment of the VOR.