Electrocochleography in Noise-induced temporary threshold shift

Nam, Eui Cheol

Abstract

BACKGROUND AND OBJECTIVES
Early detection and monitoring are the most important measures in the prevention of development and progression of noise-induced hearing loss (NIHL). Electrocochleography (ECoG) is known as a sensitive evoked-response test to evaluate changes in cochlear function. Through the investigation about the changes of ECoG in development of noise-induced temporary threshold shift (NITTS), we intended to evaluate the usefulness of ECoG on early detection of NIHL.
MATERIALS AND METHODS
Ten healthy adult participants (20 ears) were exposed to 90.3~105.0 dB broad-band noise for 3 hours in a computer-game room. Pure-tone audiometry (PTA) and ECoG were performed before the exposure, immediately after and 24 hours after the exposure.
RESULTS
Before the exposure, mean PTA threshold was 6.1+/-2.6 dB, which was significantly increased to 12.0+/-3.2 dB immediately after the exposure, and recovered to 5.5+/-2.4 dB at 24 hours later. Marked increment of SP/AP (summating potential/action potential) ratio was observed simultaneously with the development of TTS and was normalized after its resolution. The mean ratio was 0.23+/-0.17 before the exposure, 0.43+/-0.16 on TTS phase, and 0.24+/-0.18 on resolution.
CONCLUSION
The result of this study suggest that SP/AP ratio of ECoG might have applicability for early detection and monitoring of NIHL.