Ocular vestibular evoked myogenic potentials in response to three test positions and two frequencies.

Abstract

To determine how eye closure, test positions, and stimulus frequencies influence ocular vestibular evoked myogenic potentials. This study used a within-subjects repeated measures design. Twenty asymptomatic subjects were each tested on ocular vestibular evoked myogenic potentials in three head/eye conditions at 500 Hz and 1,000 Hz using air-conducted sound: 1) sitting upright, head erect, eyes open, looking up; 2) lying supine, neck flexed 30°, eyes open, looking up; and 3) lying supine, neck flexed 30°, eyes closed, relaxed. The four dependent variables measured were n10, p16, amplitude, and threshold. Supine/eyes open was comparable to sitting/eyes open and better than supine/eyes closed. Eyes closed resulted in lower amplitude, higher threshold, and prolonged latency. Significantly fewer subjects provided responses with eyes closed than with eyes open. No significant differences were found between both eyes open conditions. Both n10 and p16 were lower at 1,000 Hz than at 500 Hz. Amplitude and threshold were higher at 1,000 Hz than at 500 Hz. Supine/eyes open is a reliable alternative to sitting/eyes open in patients who cannot maintain a seated position. Testing at 1,000 Hz provides a larger response with a faster onset that fatigues faster than at 500 Hz. The increased variability and decreased response in the eyes closed position suggest that the eyes closed position is not reliable. 3b.