The effect of gaze direction on the ocular vestibular evoked myogenic potential produced by air-conducted sound

Abstract

To assess the effects of vertical and horizontal gaze, head rotation, body position, and vision on the ocular vestibular evoked myogenic potential (OVEMP) produced by air-conducted (AC) sound. Ten normal subjects were stimulated by 500 Hz 2 ms AC tone bursts at 136-142 dB peak SPL. OVEMPs were recorded from electrodes placed beneath the eyes. Angles of vertical gaze ranged from maximal downward to upward gaze in increments of 5-10 degrees . Horizontal gaze was measured during elevation and ranged from 20 degrees adduction to 20 degrees abduction. Increasing vertical gaze increased OVEMP amplitude, especially for the contralateral eye (neutral vs maximal upward gaze; contra: 1.0 vs 2.6 microV; ipsi: 0.8 vs 0.9 microV; P<0.001). OVEMPs from the contralateral eye peaked significantly earlier in the upward gaze positions (contra: 9.2 ms; ipsi: 10.4 ms; P<0.001), but peaked later during downward gaze (contra: 14.2 ms; ipsi: 11.4 ms; P=0.014). There were small effects of horizontal gaze and supine body position, but no effects of head rotation or vision. OVEMP amplitudes are strongly modulated by gaze position. Truncal position also affects OVEMP amplitude. This study quantifies the effect of gaze on the OVEMP and demonstrates the importance of controlling for gaze in clinical and experimental studies.