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.