First Human Intra-Operative Measurements of EMG Responses from Stapedius Muscle

The stapedius muscle is the smallest muscle in the body. Electrically evoked stapedius reflex thresholds (eSRT) correlate with the maximum comfort levels (MCL) perceived by cochlear implant (CI) recipients. Nowadays, eSRT measurements can be used to fit the CI`s especially in non-cooperative patients like small children, however, the fitting process remains manual and is time consuming.

Measurement of the eSRT by the implant itself may allow for automatic fitting of cochlear implants without the need for audiologic intervention. The implant would also be capable of autonomic adjustments to the fitting map in function of changing of the stimulation environment as e.g. in the case of changing contact impedances.

The first human EMG-measurements from the stapedius muscle using a recording electrode will be presented. The results obtained in patients undergoing cochlear implantation for treatment of unilateral deafness will cover EMG-responses of acoustic and electrical stimulation. Aspects of electrode placement and surgical technique necessary to measure EMG responses from the stapedius muscle will be discussed and shown is a short video. In addition, the non-traumaticity of the placement of the recording electrode in contact with the stapedius will be demonstrated by tympanometric post-operative follow-up eSRT measurements.