HIGH-FREQUENCY AUDIOMETRIC MONITORING STRATEGIES FOR EARLY DETECTION OF OTOTOXICITY

Therapeutic drugs such as the aminoglycoside antibiotics (AMG) and the chemotherapy agent cisplatin (CDDP) are known to cause irreversible h earing loss, typically affecting highest frequency hearing first with progression of loss to the lower frequency regions. Conventional (0.25 -8 kHz) and high-frequency (9-20 kHz) serial hearing threshold monitor ing was done in 123 hospitalized patients (222 ears) administered AMG or CDDP. Of ears showing a decrease in sensitivity corresponding with treatment, 62.5% demonstrated initial hearing loss solely in the high- frequency range, 13.5% first showed loss only in the conventional-freq uency range, and 24.0% showed loss in both frequency ranges concurrent ly. Thus, if only high frequencies had been monitored, early change in auditory sensitivity would have been detected in 86.5% of these patie nts. Further analysis revealed a range of five frequencies, specific t o each individual's hearing threshold configuration, in which initial ototoxicity appeared most likely to be detected. Testing only these fi ve frequencies would have identified 89.2% of ears that showed change. The results of this study confirm the need to serially monitor audito ry thresholds, especially in the high-frequency range, of patients rec eiving ototoxic drugs. A shortened five-frequency monitoring protocol is presented and suggested for use with patients unable to tolerate le ngthy audiometric testing procedures.