The Effect of Intracochlear and Intratympanic Dexamethasone on Cochlear Implant Impedance

This study investigated the impact of different local corticosteroid applications on impedance measurements in patients with cochlear implants.

The study was designed as a controlled, randomized, and prospective study in which 34 consecutive patients who had undergone cochlear implant surgery were divided into three groups. The first group received intracochlear dexamethasone, in the second group the middle ear cavity was filled with dexamethasone, and the third group did not receive dexamethasone. Intraoperative, postoperative 1^st week, 1^st month, 3^rd month, 6^th-month neural response telemetry, and impedances were measured. The measurements were compared by electrode groups representing the different regions of cochlea like basal (1-7), middle (8-13), and apical (14-22) regions.

The intergroup analysis showed no statistically significant differences in impedance measurements of the basal, middle, and apical regions (p>0.05). However, the impedances were lower in the two dexamethasone groups, especially in the basal and middle parts. Sixth month impedances were also lower in the dexamethasone groups. There was apparent stability in the impedance of the basal region with the intracochlear application during the first week.

Local dexamethasone applications had a potentially positive impact on the impedance of the basal and middle regions. Patients had lower impedances than the control group during follow-up and at the endpoint. The increase in the apical region may indicate that dexamethasone was not reaching the apical zone in local applications.