Intraoperative eSRTs: Feasibility of Measurement and Correlation With Postoperative eSRTs.

Abstract

Objective: To assess the feasibility of intraoperative visual electrically evoked stapedial reflex threshold (eSRT) measurement using the Cochlear SmartNav 2 system, the correlation between intraoperative and postoperative eSRTs, and the correlation between eSRTs measured at 1 and 6 months post-activation.

Study design: Prospective.

Setting: Cochlear implant (CI) program at a tertiary medical center.

Patients: Fourteen adult CI users.

Main outcome measures: Intraoperative eSRTs and postoperative eSRTs.

Results: Intraoperative eSRTs were successfully measurable on 11 of 14 participants and took approximately 3 minutes to measure. The mean intraoperative eSRT was 13.3 charge units higher than the mean 1-month post-activation eSRT (p < 0.0001). The mean difference between the intraoperative and 1-month post-activation eSRT was 17.5, 15.3, 11.1, 10.5, and 11.8 nC/phase for electrodes 1, 6, 11, 16, and 22, respectively. The combined intraoperative eSRT data for all patients and all electrodes had a standard deviation of 8.5 charge units, whereas the combined 1-month post-activation eSRT data had a standard deviation of 3.2 charge units demonstrating greater intraoperative variability. The mean difference between the 1-month and 6-month post-activation eSRT was 0.2 charge units (p > 0.999).

Conclusions: Intraoperative eSRT measurement is feasible and time-efficient in adult CI patients. The mean difference between the intraoperative and 1-month post-activation eSRT is similar across the array. However, intraoperative eSRTs are more variable than post-activation eSRTs, and thus, further investigation is needed to reduce this variability and create a clinically useful correction factor. Finally, postoperative eSRTs are stable over time.