Electrocochleography is more sensitive than distortion-product otoacoustic emission test for detecting noise-induced temporary threshold shift.

Abstract

We investigated and compared the usefulness of the electrocochleography and distortion product otoacoustic emission tests for detecting the earliest noise-induced damage by analyzing the sensitivity and specificity of the 2 tests. A prospective study. After listening to music at 90.3 +/- 4.2 dB in the same night-club for 2 hours continuously, 23 healthy normal ears experienced a temporary threshold shift exceeding 5 dB. Pure-tone audiometry, the distortion product otoacoustic emission test, and electrocochleography were performed before, immediately after, and 24 hours after the exposure. Before exposure, the measured distortion product/noise floor was 9.8 +/- 10.4, 23.5 +/- 6.4, 18.7 +/- 6.4, and 19.1 +/- 5.6 dB sound pressure level (SPL) at frequencies of 1, 2, 3, and 4 kHz, respectively. Immediately after exposure, it decreased significantly at 2, 3, and 4 kHz to 16.6 +/- 7.6, 12.5 +/- 6.8, and 14.8 +/- 7.7 dB SPL, respectively. Marked increases in the amplitude of the summating potential and summating potential/action potential ratio were recorded from 0.15 +/- 0.06 to 0.32 +/- 0.11 and 0.23 +/- 0.06 to 0.44 +/- 0.08, respectively. The respective sensitivity and specificity of electrocochleography were 76.7% to 88.5% and 91.0% to 100%. Those of the distortion product otoacoustic emission test were 54.8% to 62.2% and 75.5% to 87.0%, respectively. Electrocochleography appears to provide more sensitive and specific information than the distortion product otoacoustic emission test for detecting a noise-induced temporary threshold shift.