Effects of plateau time and ramp time on ocular vestibular evoked myogenic potentials

The responses of ocular vestibular evoked myogenic potential (oVEMP) vary significantly with the type and setting of the stimuli. This work was to investigate the effects of different ramp time and plateau time on oVEMP latency and amplitude. Twenty-two healthy volunteers aged from 20 years to 39 years were enrolled. The oVEMPs were acquired with the eyes upwards-gaze 30 degree above the head, and the sound stimuli included 0.1-ms click, and 500-Hz short tone burst (STB) of rise-plateau-fall time of 0.5-2-0.5 ms, 0.5-4-0.5 ms, 2-2-2 ms, and 2-4-2 ms. The response rate of click oVEMP (66%) was lower than STB oVEMP (100%). The click oVEMP amplitude was significantly smaller (p < 0.01, one-way ANOVA and post-hoc Scheffe procedure). The latency n1 increased by 1.4 ms as the rise/fall time shifted from 0.5 ms to 2 ms for STB stimuli. However, the latency and amplitude did not show significant difference between the STB stimuli with different plateau times. The lower amplitude and response rate for click oVEMP were associated with its lower mechanical energy of click, especially the energy from 500 to 1000 Hz.