[Asymmetrical hearing loss following symmetrical acute acoustic trauma]

Abstract

Due to diffraction, acute acoustic trauma usually causes symmetrical hearing loss. Acoustical shadow effects are relevant only at distances greater than 1 m to the sound source and frequencies greater than 1000 Hz. In case of pronounced asymmetrical hearing loss causal connection to acute acoustic trauma is unlikely. We describe two cases with pronounced asymmetrical hearing loss in spite of symmetrical acute acoustic trauma. In the first case two patients headed an exploding giant tyre in a distance of approximately 1-2 m. One of them--as expected--got a symmetrical inner ear damage. On the other hand the other patient, which stayed directly besides him, got a pronounced asymmetrical inner ear damage. In an additional case we found also asymmetrical inner ear damage after symmetrical noise exposure. In this case it was detected, that years ago the patient suffered from a menieriform attack in the now worse ear. Occult inner ear damage is discussed as a reason for the phenomenon of pronounced asymmetrical inner ear damage after symmetrical noise exposure.