The Effect of Contralateral Acoustic Stimulation on the Latency of Distortion Product Otoacoustic Emissions

Woo, Hoon Young; Chung, Sang Won; Han, Dong Hoon; Cho, Chul Kyu; Choi, Chan

Abstract

BACKGROUND AND OBJECTIVES
The auditory efferent system -Medial olivocochlear bundle (MOCB)-controls the sensitivity and frequency selectivity of the cochlea and maintains the cochlea for optimal acoustic signaling. Contralateral acoustic sound stimulates the MOCB and has inhibitory effects on the sound evoked amplitude response of the cochlea. There are only a few reports on the latency response of contralateral acoustic stimulation (CAS) on distortion product otoacoustic emission (DPOAE), and it has no consistent conclusion. The purpose of this study was to evaluate whether changing the latency of DPOAE by CAS could be a stable method for monitoring the function of MOCB. SUBJECTS AND METHOD: The change in the latencies of DPOAE after CAS were monitored in 24 normal hearing ears with f2 sweep paradigm. The CAS level was divided into two groups, one was under 65 dB SPL and other was over 65 dB SPL. RESULTS: As f2 frequency changed from 1 kHz to 2 kHz, the latency of DPOAE was shortened from 11.82 +/- 1.87 ms to 7.29 +/- 0.86 ms in low stimulation level (50 dB SPL) and from 10.70 +/- 2.65 ms to 6.16 +/- 1.59 ms in high stimulation level (75 dB SPL) There were no significant shortening on the latency of DPOAE after CAS in low stimulation level group. But in higher stimulation level group (75 dB SPL), DPOAE latency changed from 10.70 +/- 2.65 ms to 10.12 +/- 1.95 ms (CAS level: 35 dB SL) and to 9.76 +/- 2.97 ms (CAS level: 50 dB SL) in 1 kHz, from 6.16 +/- 1.59 ms to 5.96 +/- 1.49 ms (CAS level: 35 dB SL) and to 5.83 +/- 1.28 ms (CAS level: 50 dB SL) in 2 kHz. CONCLUSION: Changes in the latency of DPOAE after CAS is not a stable monitoring tool for the function of MOCB.