A sheep model for electrically and accustically evoked stapedius reflex threshold measurement by electromyography

Objective Electrically evoked stapedius reflex threshold (ESRT) measurements are a standard tool for intraoperatively cochlea implant (CI) fitting. Currently, it is crucial to visualize the stapedial tendon in order to evaluate whether the reflex was successfully elicited or not. This is subjective and sometimes impossible because of the movement of surrounding tissue or limited view on the stapes structures. This project is aimed to develop an objective evaluation of the stapedius reflex (SR) by monitoring electromyographic (EMG) activity of the stapedius muscle (SM).

Methods The stapedius reflex was measured in 4 adult female sheep. The reflex was evoked contralateral acoustically (via a tympanometer) and ipsilateral electrically via a priorly implanted CI.

The placement of the EMG electrodes is done by exposing the SM via a retro-facial approach. A hole was drilled at the basis of the mastoid and the facial nerve was dissected. The lateral edge of the SM was exposed. For the contralateral acoustic stimulation, a probe was placed within the outer ear channel and connected to a tympanometer. During contralateral acoustic or ipsilateral electric stimulation, the EMG was recorded.

Results In all preparations, the SM was successfully exposed without complications. In every case, the electrodes could be placed within the muscle, and it was possible to record the SR with the EMG electrodes.

Conclusions Our acute trials have shown promising results in recording EMG to objectify the evaluation of the SR intraoperatively. This technique has the potential, once translated into human surgeries, to improve the outcome of CI implantations.

Poster-PDF A-1858.PDF

Publication History

Article published online:
10 June 2020