Intratympanic dexamethasone injection effects on transient-evoked otoacoustic emission

To investigate the effects of intratympanic dexamethasone injection, which is done because of tinnitus, on transient evoked otoacoustic emission (TEOAE) and so determine whether given dexamethasone cause any damage in the inner ear.

Twenty-six patients, aged between 32 and 75, with subjective tinnitus, were randomly selected. The selected patients were the ones whose improvement had not been achieved through minimum 6 months' medical therapy (eg, Ginkgo biloba extract EGb 761, betahistidine, and trimetazidin) and who were free of systemic or otolaryngologic disease (hypertension, diabetes mellitus, hypo/hypertyroidi, hypercholesterolemia, Meniere disease, and otosclerosis). Before and after the injections, audiometry including high-frequency tinnitus matching and TEOAE tests were done. The injections of 4 mg/mL dexamethasone were done 5 times in fixed protocols on days 0, 2, 4, 6, and 8. After each injection, the patients were kept supine for 60 minutes with the head turned 45 degrees to opposite ear. Paired t test was used to compare the beginning and final measurements.

Temporary pain and vertigo attacks which lasted at most for 15 minutes occurred in some patients only during injections. Neither infection nor persistent perforation occurred in any patients. After the management, there was no significant difference on patient's pure tone averages ( P = .067) and high-frequency averages ( P = .592). When the obtained TEOAE results before and after management were compared, the only significant increase was detected in the reproducibility values ( P = .042). There was no significant difference in other TEOAE parameters which are stimulus stability, stimulus intensity, and overall signal-to-noise ratio ( P > .05). There is no fixed criteria for rejecting a response solely on the reproducibility. However, a high value of the reproducibility (or increase in reproducibility) is always meaningful.

Intratympanic dexamethasone used for management in many indications, primarily in Meniere and tinnitus patients, was found to increase the reproducibility values of otoacoustic emission. Despite the fact that there was not a reasonable increase in the responses coming from the outer hair cells, the result was considered positive for the study as the responses did not decrease. It is found out that 4 mg/mL dexamethasone given intratympanically does not adversely affect the outer hair cell function as measured by otoacoustic emission. Within the limits of this study, dexamethasone appears to be safe when given intratympanically.