Monitoring of the Inner Ear Function During and After Cochlear Implant Insertion Using Electrocochleography

Abstract

To preserve residual hearing during cochlear implant (CI) surgery, it is desirable to use intraoperative monitoring of inner ear function (cochlear monitoring), especially during electrode insertion. A promising method is electrocochleography (ECochG). Within this project, the relations between ongoing responses (ORs), recorded extra-and intracochlearly (EC and IC), and preservation of residual hearing were investigated. Before, during, and after insertion of hearing preservation electrodes, intraoperative ECochG recordings were performed EC using a cotton wick electrode and after insertion also IC using the CI electrode (MED-EL) and a research software tool. The stimulation was delivered acoustically using low frequency tone bursts. The recordings were conducted in 10 adult CI recipients. The amplitudes of IC ORs were detected to be larger than EC ORs. Intraoperative EC thresholds correlated highly to preoperative audiometric thresholds at 1000 Hz, IC thresholds highly at 250 Hz and 500 Hz. The correlations of both intraoperative ECochG recordings to postoperative pure tone thresholds were low. When measured postoperatively at the same appointments, IC OR thresholds correlated highly to audiometric pure tone thresholds. For all patients, it was possible to record ORs during or directly after electrode insertion. Consequently, we conclude that we did not observe any cases with severe IC trauma. Delayed hearing loss could not be predicted with our method. Nevertheless, intraoperative ECochG recordings are a promising tool to gain further insight into mechanisms impacting residual hearing. Postoperatively recorded IC OR thresholds seem to be a reliable tool for frequency specific hearing threshold estimation.

Correlation between Speech Perception Outcomes after Cochlear Implantation and Postoperative Acoustic and Electric Hearing Thresholds

“…However, the clinical relevance of EcochG data for CI users has been reported in the literature according to a recent systematic review [ 37 ], which shows hearing preservation as an important and highly discussed topic. Correlation analyses between postoperative hearing thresholds and EcochG recordings have been reported in the literature [ 38 , 39 , 40 ] and were not part of this study.…”

Correlation Between Electrocochleographic Changes During Surgery and Hearing Outcome in Cochlear Implant Recipients: A Case Report and Systematic Review of the Literature

“…Five articles (5,9,(12)(13)(14) analyzed extracochlear ECochG recordings. Three articles are published by the same research group (5,9,13), including different subjects each time.…”

“…Three articles are published by the same research group (5,9,13), including different subjects each time. Adunka et al (12) included 31 and Haumann et al (14) 10 subjects. Both studies found no correlation between changes of extracochlear ECochG recordings and hearing threshold changes 4 weeks after surgery.…”

A simple tool to automate the insertion process in cochlear implant surgery

“…The implementation of a tool like the CHD could bring other benefits. For example, the device could later on be combined with additional intraoperative measurements such as fluoroscopy [39], or cochlear monitoring [40] in order to achieve a deeper understanding of the electrode insertion process and the underlying mechanism of intracochlear trauma. Ultimately, more information and strategies could be gathered to develop different approaches that could guarantee preservation of residual hearing.…”