Effects of gentamicin on sensorineural elements of the cochlea in human temporal bones

Purpose Gentamicin is commonly prescribed for treatment of gram-negative bacterial infections. It has, however, been known to have vestibulotoxic and ototoxic effects in humans. Previous studies were confounded by the use of other types of ototoxic drugs, higher than therapeutic doses, and prolonged time periods between gentamicin administration and death. The purpose of this study is to observe the effects of parenteral gentamicin administration on the sensorineural elements of the cochlea in which the previously described factors did not exist. Materials and methods Temporal bone specimens were divided into 2 groups. Group 1 included 16 "normal" temporal bones with no history or histopathologic findings of otologic disease or ototoxic drug administration, and group 2 included 17 temporal bones that received gentamicin treatment within 6 months before death. Temporal bones were excluded from group 2 if patients had histopathologic findings or history of otologic disease and/or other ototoxic drugs. All temporal bones were examined under light microscopy. Results The percentages of intact outer hair cells in the basal turn was significantly greater in group 1 compared with group 2. There was no significant difference in hair cell number between the groups in the other turns. There was no significant difference in the number of spiral ganglion cells between groups in any turn. Conclusion Although gentamicin is primarily considered to be vestibulotoxic, this study showed that gentamicin can damage sensorineural elements of the cochlea, even in younger patients. During the administration of this drug, hearing of the patient should be carefully monitored.