Feasibility of Obtaining Intraoperative Electrically Evoked Stapedial Reflex Thresholds (eSRT)

To assess the rate of obtaining intraoperative eSRT measurements in primary cochlear implant (CI) recipients while limiting the use of volatile anesthetics, such as sevoflurane.

In this prospective cohort study, thirty-one patients who underwent CI surgery with a Cochlear Americas device from January 2023 through March 2024 were included. Intraoperative eSRT testing at electrodes E1, E6, E12, E17, and E22 was performed on all patients. Sevoflurane was discontinued and confirmed undetectable at least 10 min prior to eSRT testing to avoid diminishing the stapedial reflex. The primary outcome measure was eSRT response rate at any electrode or pulse width.

Thirty-four CIs were placed in 31 patients, including three bilateral recipients. Eighty-five percent (29/34) of implants had at least one response at any electrode or pulse width; 71% (24/34) at pulse width 25 μs; and 82% (28/34) at 25 or 37 μs. Response rates were significantly higher at apical (E17, E22) and middle (E12) electrodes compared to basal electrodes (E1, E6) (p = 0.004). Comparisons also revealed significantly different eSRT values between apical, middle, and basal electrodes (p < 0.0001). Specifically, the basal electrode region had a greater median threshold (30.5 nC/phase) than apical (18.3 nC/phase; p < 0.0001) and middle (17.7 nC/phase; p < 0.001) regions.

Intraoperative eSRT is a feasible and effective way of obtaining an objective measurement that can potentially guide CI programming. Subsequent studies will investigate the relationship between intraoperative and postoperative eSRT in this patient cohort and determine how intraoperative eSRT may facilitate CI programming.