Electrocochleography in Noise-Induced Hearing Loss

Nam, Eui Cheol

Abstract

BACKGROUND AND OBJECTIVES
Electrocochleography (ECoG) is a sensitive evoked-response test for evaluating changes in cochlear function. We investigated the extratympanic ECoG in noise-induced temporary and permanent threshold shift to evaluate the usefulness of ECoG in the early detection and monitoring of noise-induced hearing loss (NIHL). SUBJECTS AND METHOD: Fifteen healthy ears were exposed to noise to induce temporary threshold shift (TTS). Pure-tone audiometry and ECoG were performed before (control-group), immediately after (TTS-group), and 24 hours after the exposure. And ECoG was measured in 27 ears with noise-induced permanent threshold shift (PTS-group). RESULTS: The mean amplitude of SP (summating potential) was greatest in the TTS-group. The largest increment in the SP/AP (action potential) ratio was also observed in the TTS-group. The mean ratios of control-, TTS-, and PTS-group were 0.22+/-0.11, 0.46+/-0.18 and 0.37+/-0.10, respectively. The PTS-group showed the smallest mean amplitude of AP. CONCLUSION: The results of this study suggest that SP, AP and the SP/AP ratio might be sensitive parameters reflecting the changes of cochlear function in NIHL.