HIGH-FREQUENCY TESTING TECHNIQUES AND INSTRUMENTATION FOR EARLY DETECTION OF OTOTOXICITY

Veteran patients with certain types of infections and cancers are rout inely treated with therapeutic agents having ototoxic potential, thus threatening loss of hearing sensitivity which preexists in the majorit y of these patients. To prevent communication deficits requiring inter vention, this laboratory is developing instrumentation and techniques for early detection of ototoxicity. For this study, conventional (less -than-or-equal-to 8 kHz) and high-frequency (greater-than-or-equal-to 8 kHz) hearing thresholds were monitored behaviorally in hospitalized veterans receiving treatment with ototoxic drugs. Data analysis reveal ed that monitoring only the high-frequency range would have identified 67% of ears showing change. A five-frequency range of hearing, specif ic to each individual, was identified for its high sensitivity to earl y ototoxic change. Monitoring of only these five frequencies in each p atient would have identified 82% of ears that showed behavioral change . Auditory brainstem responses (ABR) were obtained in a subgroup using clicks and high-frequency (8-14 kHz) tone bursts. ABR latency/morphol ogy changes were observed in 95% of ears demonstrating behavioral chan ge. High-frequency tone-burst-evoked ABRs alone would have identified 93% of initial changes. Monitoring of high-frequency audition using th ese techniques shows promise for early detection of ototoxicity with p otential for prevention of hearing loss in frequencies essential for v erbal communication.