Aminoglycoside ototoxicity: A human temporal bone study

Objective. Hearing loss after aminoglycoside administration has been thought to result primarily from. hair cell injury. The purpose of the study was to determine the potential for direct injury of spiral ganglion cells and hair cells in cases of documented human aminoglycoside ototoxicity. Study Design: Retrospective case review. Methods: The clinical course of two individuals with aminoglycoside ototoxicity are documented, including the details of administration of tobramycin and other ototoxic medication and serial audiograms. The temporal bones were processed, and the cochlear elements quantified. Results. Histopathological study of the temporal bones from the individuals in the study demonstrated reduction of both ganglion cell and hair cell populations. Spiral ganglion cell loss was not necessarily subadjacent to areas of hair cell loss in cases of aminoglycoside ototoxicity. Instead, spiral ganglion cell reduction may be present in segments of the cochlea with normal-appearing hair cells. Conclusions: The study suggests that aminoglycoside antibiotics can injure spiral ganglion cells directly, as well as hair cells. Thus, the characteristic hearing loss of ototoxicity can result from degeneration of either cochlear element.