Intraoperative Acoustic Monitoring Using Threshold and Suprathreshold Pure Tone Audiometry during Cochlear Implantation Under Local Anesthesia: A Simple and Novel Method to Potentially Enhance Hearing Preservation Cochlear Implant Surgery.

Abstract

Objective: To report the feasibility and potential utility of monitoring acoustic hearing on awake patients using intraoperative behavioral responses to threshold and suprathreshold stimuli while undergoing cochlear implantation (CI) under local anesthesia, without any form of sedation.

Study design: Retrospective review of the first five cases performed by one surgeon.

Setting: Tertiary care academic medical center.

Patients: Adult patients with residual acoustic hearing undergoing CI.

Interventions: CI under local anesthesia, without any form of sedation.

Main outcome measures: Procedural tolerance, reliability of intraoperative pure tone threshold and suprathreshold audiometry, and correlation of intraoperative findings with early postoperative residual hearing.

Results: Five ears in four patients underwent CI, including three males and one female, with a median age of 61 years. Intraoperatively, patients reported reliable behavioral responses to pure tone threshold and suprathreshold stimuli and provided real-time feedback on perceived stimulus change to the surgeon just prior to, during, and immediately following electrode insertion. All patients were able to complete the operation under local anesthesia. During electrode insertion, three cases reported no change and two cases reported diminished stimulus perception that reversed with limited electrode pull back near terminal insertion. Immediate postoperative audiograms demonstrated preservation of bone conduction thresholds within 10 dB of their preoperative baseline for all cases, suggesting hearing preservation. Three-month postoperative AzBio in quiet scores were available for two patients, measuring 45% and 94%, respectively.

Conclusions: This report describes the feasibility of intraoperative behavioral audiometry during CI under local anesthesia, using patient feedback during electrode insertion to optimize hearing preservation surgery. Akin to other surgical subspecialties that use real-time patient feedback where objective intraoperative measures of neurofunction are imperfect, we demonstrate feasibility and potential utility of live acoustic monitoring during CI.