Utility of headshake versus whole-body VOR evaluation during routine electronystagmography.

Evaluation of the vestibulo-ocular reflex (VOR) by caloric testing yields important localizing information, but does not examine the entire frequency spectrum of vestibular function. With the addition of head rotation at 0.5 Hz (50 deg/s) and a velocity sensor to measure head movement, additional unique information regarding higher frequency VOR function can be readily obtained using standard electro-oculography (EOG). Over the past 4 years, active head-on-body and passive whole-body rotation testing with four-channel strip-chart recording and hand analysis have been routinely performed on every patient referred for caloric testing. In 95 percent of cases with normal symmetric caloric responses, headshake VOR gain with either stimulus was normal (greater than 0.51). Similarly, more than 95 percent of patients with unilateral deficits on caloric testing yielded normal rotational VOR gains. In contrast, roughly one third of patients with bilaterally reduced caloric responses demonstrated both abnormally low active headshake and passive whole-body rotational gain (less than 0.5). It appears, therefore, that both active head-on-body and passive whole-body rotation VOR testing at 0.5 Hz are possible using standard recording techniques, and yield valuable added information in cases with reduced bilateral caloric responses.