[Frequency properties of bone-conducted vibration and sound-induced ocular evoked myogenic potential]

Objective: The present study was to compare the frequency characteristics of bone- conducted vibration (BCV) and air-conducted sound-induced ocular vestibular evoked myogenic potential(oVEMP) with different stimulation settings, so as to select an optimal setting. Methods: Bruel and Kjaer artificial mastoid was used to calibrate bone vibrator, the mini-shaker. The outputspectrum and transient waveform were recorded when the input frequency was set at different frequencies and data were further analyzed to get the peake quivalent force level value of the output vibration. oVEMP was recorded as we previously reported with normal young adults. Response prevalence, latency, wave interval, amplitude, amplitude ratio, and bilateral amplitude asymmetry ratio were recorded and analyzed. SPSS 24.0 software was used for statistical analysis. Results: Output peak equivalent force level increased as the intensity of primary input stimulation increased at certain frequency,while it decreased as the frequency of primary input stimulation increased at certain intensity. Peak equivalent force level of 500 Hz tone burst (1-2-1) input stimulation was greatest as 139.8 dB when using mini-shaker for vibration stimulation,even greater when using bone conductor B-71.Twenty subjects were elicited with normal oVEMP with N1 and P1 waves in both ears using air-conducted stimulation or bone-conducted vibration.The response rate in these subjects was 95% and 100% respectively. The latency of N1 was (11.33±1.35) ms and (10.14±0.38) ms, latency of P1 was (16.24±1.56) ms and (15.65±1.19) ms, interval N1-P1 was (4.59±1.26) ms and (5.55±0.81) ms, symmetry coefficient was 12.22%[5.50%,21.85%] and 8.74%[3.37%,14.08%], amplitude was 3.07[2.05,4.43] μV and 3.07[2.05,4.43] μV in sound and bone conducted vibration group, respectively. The latency of N1, latency of P1, interval N1-P1, symmetry coefficient and n1-P1 amplitude of BC-oVEMP were different statistically (all P<0.05). Conclusions: 500 Hz 45 dB input stimulation setting is the optimal parameter for BC-oVEMP. BC-oVEMP can be recorded simply, safely and quickly in normal young people, thus it is a clinically practical way of measuring utricular function.