Noise-induced hearing loss. A human temporal bone case report.

The histopathology of a case of profound hearing loss which seemed to be induced by noise exposure (explosions and drillings in a gold mine) is reported. The patient's only residual hearing was 250 Hz at 90 dB SPL in the right ear. The major histopathological findings were as follows: Bilateral absence or collapse of Corti's organ was observed in the middle and basal turns of the cochlea; however, in the remaining area (approximately 6.0 mm in range in the apical portion of the cochlea) Corti's organ was well-preserved with a moderate loss in number or atrophy of the hair cells. Bilateral marked decrease of the cochlear nerve was noted in the middle and basal turns; however, the nerve was well-preserved in the remaining apical portion (approximately 6.0 mm in range) of the cochlea. These pathological findings were somewhat less severe in the right cochlea than in the left. In general, there was good correlation between the profound hearing loss and the extensive pathological findings in Corti's organ. The residual hearing in the right ear would seem to be explained by the less severe pathological changes found in the apical portion of the right cochlea than in the left cochlea. In addition to noise exposure, other possible etiological factors contributing to this hearing loss are discussed. These include diabetes mellitus and presbycusis.