Masseteric nerve position on the "temporomandibular joint-chin tip" artificial axis: an anatomical study

The use of the masseteric nerve develops in the surgery of facial paralysis rehabilitation. The objective of this study was to determine the topography of the masseteric nerve and to deduce and predict a precise and reproducible anatomical cluster to facilitate its clinical identification during V-VII neurotization surgery.

For the purpose of this work, a cadaveric study was performed on 31 hemi-faces. All dissections were performed bilaterally and comparatively, following steps aiming at simulating, as close as possible, the clinical conditions of a facial palsy rehabilitation by V-VII anastomosis.

For the identification of the masseteric nerve, bony reference points were used, i.e., the temporomandibular joint (TMJ) and the chin point (CT). A virtual axis was drawn between the TMJ and the CT, and the distance [TMJ-MN] determining the smallest length h was then plotted against the distance [TMJ-CT] determining the largest length H, thus allowing the calculation of an h/H proportion ratio (PR) indicating the proximal part of the masseteric nerve from the TMJ. The average length h between the TMJ and the NM was 3.5 cm (± 0.1 cm) from the TMJ, i.e., an average ratio h/H [TMJ-MN]/[TMJ-CT] of 28.1% 4.0 and a median ratio of 28.6% of the distance [TMJ-CT].

Our study opens new perspectives for facilitating its identification and use, offering practitioners a tool to make V-VII the neurotization procedure less complex, with the eventual prospect of a minimally invasive procedure combining imaging, surgery, and augmented reality.