Peroperative temporary threshold shift in ear surgery. An electrocochleographic study.

TTS resulting from drilling in the temporal bone was detected by means of pre- and post-exposure ECoG recordings taken during ear surgery for chronic otitis media. The TTS obtained varied between 5 and 40 dB at 4 and 8 kHz. The correlation between duration of noise exposure and magnitude of TTS was statistically significant. The results indicate that drill-induced noise in ear surgery may result in postoperative high-tone sensorineural hearing loss, and support the view that manipulation of the ossicular chain during ear surgery causes mainly a threshold shift at the lower frequencies.