Auditory-evoked potential correlates of susceptibility to noise-induced hearing loss

Correlations between changes in cochlear microphonics (CM) and auditory brainstem-evoked potentials (ABEP) resulting from transitory-threshold-shift (TTS)-inducing noise, in normally hearing subjects, and the eventual permanent threshold shift (PTS) which the same subjects developed after 9-14 months of well-quantified occupational noise were evaluated. In addition, the predictive value of pigmentation, as an indicator of eventual PTS, was assessed. Eleven CM and ABEP indices which showed significant correlation with the eventual hearing loss were identified. Eight of these indices reflect the effect of increased stimulus rate and experimental TTS-inducing noise. These results show that the difference in ABEP latencies as a result of increased stimulus rate is smaller in persons with large eventual PTS (high susceptibility to noise-induced hearing loss). The effect is larger in persons that eventually developed a small PTS (low susceptibility). Pigmentation, as reflected by iris and skin color, was found to have a negative correlation with susceptibility to noise, i.e. the more pigment the less PTS developed. The above indices may be useful to determine personal susceptibility to noise in normally hearing subjects.