A new approach in facial nerve trunk surgical identification.

Background: Considering the lack of feasible methods for the extracranial portion of the facial nerve previsualization and the high risk of its iatrogenic injures, the knowledge about facial nerve identification landmarks is critically needed. The aim of our research was to find out reliable landmarks for the surgical access of the facial nerve trunk (FNT).

Materials and methods: Our study was conducted on 75 hemifaces of adult embalmed cadavers. Prior to anatomical dissection, the cephalometric type of each head was determined and the landmarks identified for study have been established.

Results: For the FNT surgical access, 8 landmarks were measured and statistically analyzed on 5 criteria: gender, laterality, cephalometric type, branching pattern and its variant (classic/atypical). Six of the examined landmarks showed statistical significance depending on gender (p ≤ 0.05) among which were: angle of the FNT bifurcation (FNTB); distance between the FNT division and the angle of the mandible (FNTD/AM); distance between the FNT division and the apex of the mastoid process (FNTD/AMP); distance between the FNT origin and the intertragic notch (FNTO/ITN); distance between the FNT origin and the triangular prominence of the cartilage of the external acoustic meatus (FNTO/∆CEAM); distance between the FNT origin and the anterior margin of the sternocleidomastoid muscle insertion point (FNTO/AMSCMIP). The angle formed at the intersection of the facial nerve trunk with the vertical line drawn through the anterior margin of the external acoustic meatus (FNT/VEAM), was statistically significant depending on laterality (p = 0.049). The FNT bifurcation angle was also statistically significant depending on the branching pattern (p = 0.005).

Conclusions: Although seven of the studied landmarks were statistically significant based on at least one of the examined criteria, the limitations of the research include: a small number of samples, predominance of the male hemifaces, and prevalence of the mesocephalic type individuals.