The effects of ototoxicity on the auditory brain stem response and the scalp-recorded cochlear microphonic in guinea pigs.

The objective determination of hearing impairment with evoled response techniques may be of value in the early detection of ototoxic reactions, especially in infants and other "difficult" patient populations. In this study the auditory brain stem response to "clicks" at two intensities and two repetition rates were recorded from guinea pigs that had been given one of two dosage levels of kanamycin or no drug. The scalp-recorded cochlear microphonic to continuous tones was also recorded. Hearing loss was seen in one-third of the animals receiving kanamycin. The temporal course of the deficit varied considerably between animals. Auditory system change was most readily detected in response to low-intensity stimuli, while change in repetition rate of the clicks did not affect the results. The cochlear microphonic potentials correlated with the auditory brain stem response.