Changes in electrovestibular brainstem responses after aminoglycoside intoxication in guinea pigs

Objective: To verify the usefulness of short-latency vestibular responses e voked by a combination of round window electrical stimulation and sinusoida l rotation (electrovestibular brainstem responses; EVBRs) as a new monitori ng tool of the vestibular function in animal experiments. Methods: EVBRs were obtained before, during, and after treatment with amino glycosides, along with compound action potential (CAP) audiograms. The chan ges in EVBRs were compared with morphological changes observed by scanning electron microscopy. Results: EVER amplitudes did not change in the group of guinea pigs treated with amikacin, but markedly decreased in the streptomycin and gentamicin- treated groups. CAP audiograms indicated a significant threshold elevation in the amikacin group, a moderate elevation in the gentamicin group, and no change in the streptomycin group. Under scanning electron microscopy, the loss of the sensory hair cells observed in the cristae ampullares was sligh t to moderate in the amikacin group, moderate to severe in the streptomycin group, and severe in the gentamicin group. Conclusion: EVBRs reflect overall pathological changes undergone by vestibu lar hair cells, and support the vestibular specificity of EVBRs. (C) 2001 E lsevier Science Ireland Ltd. All rights reserved.