Intra-operative access of the stapedius muscle via retrofacial approach – A feasibility clinical study

Introduction The neurophysiological sensing of the stapedius muscle’s (SM) activity represents an unambiguous tool for measuring the stapedius reflex (SR). An appealing solution for the electrically evoked SR sensing is therefore to access the SM’s belly directly via retrofacial approach, which we investigated in our study with regard to its feasibility, safety, and reproducibility.

Material & Methods The 3-D reconstruction of the middle and inner-ear structures [SM, facial nerve (FN), chorda tympani (ChT), cochlea, and sigmoid sinus] of 16 selected patients undergoing cochlear implantation (CI) was created based on manually segmented computed tomography datasets. The retrofacial approach, aimed at directly accessing the SM, was performed after facial recess exposure during CI surgery. In cases of poor exposition of the SM, the access was done anterior to the FN via drilling of the pyramidal eminence (PE). 3-D reconstructions of the temporal bones were consulted during pre- and intra-operative phases.

Results The SM was accessed in 16/16 patients. In 13/16 cases the SM was accessed via retrofacial approach. The SM access was drilled posterior and medial to the mastoid portion of the FN at almost half-way between the level identified by the stapes’ head and the branching out of the ChT, according to results previously obtained on temporal bones. In the remaining 3/16 cases following intraoperative evaluation, the SM was accessed via drilling of the PE.

Conclusion Our results confirmed that it is feasible, safe, and reproducible to access the SM via retrofacial approach and will be useful in the future development of cochlear implants with an integrated autonomous and objective fitting feature.

Conflict of Interest Der Erstautor weist auf folgenden Interessenkonflikt hin Das Forschungsprojekt wird unterstützt durch MED-EL, Innsbruck

Publication History

Article published online:
24 May 2022