Surgical Identification of the Masseteric Nerve for Facial Reanimation: A Systematic Review and Meta-Analysis.

Background: The masseteric nerve is one of the most commonly utilized in facial reanimation nerve transfer surgery, though reported methods of intraoperative identification are variable. Objective: To systematically review techniques for identifying the masseteric nerve and meta-analyze pooled distances from important landmarks for facial reanimation. Methods: This was a systematic review and meta-analysis of entries on PubMed and EMBASE/Ovid, in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Results: Eleven studies with 291 nerve identification procedures were recorded. Anatomical landmarks, including the tragus, zygomatic arch (ZA), lateral canthus, temporomandibular joint, and alar, were referenced to locate the masseteric nerve. Geometric areas, including the "masseteric area" and "subzygomatic triangle," were reported. Random-effects meta-analysis revealed a pooled mean distance from the ZA to the masseteric nerve of 10.26 mm (95% confidence interval [CI]: 7.72-12.80 mm) and 33.61 mm (95% CI: 10.37-56.86 mm) from the tragus. Conclusion: Distances to the masseteric nerve from static anatomical landmarks may vary due to gender, weight, height, and ethnicity. The most reliable method to localize the masseteric nerve is to measure its distance from the ZA to define the two-dimensional area of interest and triangulate this with depth measurements from the parotidomasseteric fascia for higher accuracy in surgical dissection.