Electromyography of the stapedius muscle via a retrofacial approach and electrically evoked stapedius reflex during cochlear implant surgery: a prospective bicentric study

Abstract

Abstract Measuring the electrically evoked stapedius reflex threshold (eSRT) with electromyography (EMG) of the stapedius muscle (SM) may offer an objective approach for cochlear implant (CI) fitting. During unilateral CI surgery in 14 adult patients with single-sided deafness, a retrofacial or anterior approach were used to evaluate the feasibility of SM-EMG during acoustically and electrically elicited stapedius reflex (SR). No adverse events occurred. This neurophysiology-based method was compared with visual detection of the SR. Intraoperatively, the belly of the SM was accessed via the retrofacial approach in 11 patients and via an anterior approach in 3 patients. Objective SR determination using electrical stimulation through the CI combined with SM-EMG was feasible in 7 patients using the retrofacial approach, but in only 1 patient using the anterior approach. Overall, electrical stimulation elicited SM-EMG responses in 8 patients, whereas acoustic stimulation elicited responses in only 3 patients. When eSRT measurement via SM-EMG was possible, stimulation thresholds were equal or slightly lower than thresholds identified visually in 85% of all SR measurements. SM-EMG-based eSRT appears to be a viable approach to estimate the eSRT intraoperatively in CI users as it shows similar performance as current clinical intraoperative standard. Further investigation is needed to investigate the relationship between intraoperative SM-EMG-based eSRT and patients’ comfort levels, establish correction factors, and potentially enable integration into future closed-loop smart CI devices.