Aminoglycosides are commonly used to treat infections in CF patients and are highly ototoxic. The inci-dence of tobramycin-induced hearing loss, tinnitus, vertigo or dizziness (ototoxicity) varies widely from 0 to 56% secondary to variation in patient enrollment, dosing, audiometry, and ototoxic criteria. The aim of this study is to determine the incidence of ototoxicity after one course of once-daily IV tobramycin in CF patients. Adult CF patients with acute pulmonary exacerbations were enrolled on IV tobramycin (10 mg/kg/d, >10 days). Pure-tone audiometry was performed for standard and extended high frequencies in the sensitive range for ototoxicity (SRO). American-Speech-Language-Hearing-Association cochleotoxicity criteria were applied. Distortion product otoacoustic emissions (DPOAE) and the words-in-noise-test (WINT) were as-sessed. Tinnitus Functional Index (TFI) and Vertigo Symptoms Scale (VSS) were used. Eighteen CF patients, mean age 31.1 (18-59), were enrolled. The incidence of cochleotoxic change from baseline at 2 and 4 weeks post-treatment was 89% and 93%. For DPOAE, a measure of outer hair-cell function, the incidence of >5 dB decrease was 82% and 80%. For WINT, a measure of word recognition, the incidence of >10% decrease was 17% and 40%. For TFI, the incidence of >10pt increase was 12% and 8%, and for VSS, the incidence of >6pt increase was 0% and 8%. One course of IV tobramycin was sufficient to cause hearing loss and other ototoxic symptoms four weeks after treatment ended. Audiometric measures were more sensitive to ototoxic change than TFI & VSS. Age and duration of tobramycin treatment were not obvious factors for predicting ototoxicity. (c) 2020 European Cystic Fibrosis Society. Published by Elsevier B.V. All rights reserved.

The frequency-modulation following response (FMFR) is a steady-state evoked response which may be a neural correlate of frequency discrimination. Aged subjects with normal hearing have abnormal frequency discrimination for low carrier frequencies and thus it might be predicted that aged individuals would have reduced FMFR amplitudes compared to young subjects. In this study, FMFR amplitudes were measured for frequency-modulated sinusoids with a carrier frequency of 0.5 kHz (80 dB SPL). In Experiment 1, the modulation depth was held constant (80%) and the modulation rate was varied (4–38 Hz), whereas in Experiment 2 the modulation rate was held constant (38 Hz) and the modulation depth was varied (0–80%). Aged subjects had significantly larger FMFR amplitudes than young subjects for certain stimulus parameters, although individual variability was large. Such results would not be predicted given previous data regarding frequency discrimination, but are consistent with several reports of larger-than-normal amplitudes of middle latency and late responses in aged subjects.

Wave V of the auditory brainstem response was measured to two 50-ms broadband noise bursts separated by silent gaps of varied duration (4, 8, 32, or 64 ms) for younger and older adults with normal hearing. All subjects had measurable wave V responses to the first noise burst. However, for the second noise burst, three of eight older adults did not have responses with gap durations of 4 and 8 ms, and one of eight younger adults did not have a measurable response with a gap duration of 4 ms. When responses were present for older adults, latencies were similar to those of younger subjects but amplitudes were smaller. These results suggest age-related deficits in gap detection at the level of the brainstem in a group of aged subjects with no threshold elevation. Results are similar to those of Boettcher et al. (1996) using an identical paradigm in young and aged Mongolian gerbils.

This study measured the masking level difference (MLD) for both 500-Hz tone detection and spondee word recognition in two groups of listeners. One group consisted of 9 elderly listeners with normal audiometric sensitivity bilaterally, up to at least 2000 Hz. The other group was a control group of 10 young listeners with normal hearing. The intent was to determine whether the elderly listeners exhibited a reduction in binaural performance that might contribute to the difficulties many such listeners have in understanding speech in noisy situations. By measuring MLDs in elderly listeners in the absence of marked peripheral hearing loss, it was hoped that any observed changes in MLD could be more strongly attributed to central effects. For both tone detection and speech recognition, it was found that the elderly performed more poorly than the young listeners, primarily on the NoS pi condition.