To Use the Back-up Cochlear Implant or Not? Using Intra-operative Impedance to Guide Your Decisions. Issue 4 (2nd April 2022)

• Record Type: Journal Article
• Authors: Mehta, Nishchay; Chu, Philip; Birman, Catherine S.
• Is Part Of: Otology & neurotology. Volume 43:Issue 4(2022)
• Page Start: e408
• Page End: e413
• Publication Date: 2022-04-02
• Subjects: Cochlear implant -- Decision-making -- Impedance; Otology -- Periodicals; Ear -- Diseases -- Periodicals; Skull base -- Surgery -- Periodicals; 617.8005
• DOI: 10.1097/MAO.0000000000003483
• Languages: English
• ISSNs: 1531-7129

Abstract

Abstract : Introduction: Intra-operative electrophysiological testing is being increasingly used to determine device functionality. Impedance abnormalities (open or short circuits) measured at time of surgery pose a dilemma: is it likely to resolve or is it a permanent fault? There is little in the literature on how to manage these intraoperative finding and if, at time of surgery, the back-up device should be used. Methods: We routinely undertake impedance testing twice intraoperatively, as well as at switch on, 1 and 3 months postoperatively. Retrospective impedance thresholds were analysed for one surgeon's cases between January 2018 and December 2019. Results: There were 235 cochlear implants performed for 217 patients (5, 020 electrode contacts) analysed. Thirty-three electrodes had abnormal impedance thresholds on first intraoperative cycle of testing, 76% resolving with the second testing cycle electrode contacts that demonstrated abnormal impedance during both intraoperative test cycles were 16.54 times (95%CI 2.55–107.13, p = 0.003) more likely to be abnormal at three months. Fifty percent resolved by switch on. The intraoperative abnormalities made up 26% of electrode abnormalities seen at 3 months postoperatively. Discussion: This study demonstrates the utility of 2 cycles of intraoperative impedance testing, with persistently abnormal electrodes having 16 times the likelihood of persistent abnormalities of impedance, and 50% resolution. These persistent intra-operative abnormal electrodes are responsibly for 26% of electrode abnormalities at 3 months. This information is useful for the surgeon when considering use of the backup cochlear implant device.