Cadaveric Study of Topographic Anatomy of Temporal and Marginal Mandibular Branches of the Facial Nerve in Relation to Temporomandibular Joint Surgery.

ABSTRACT

PURPOSE: Detailed anatomy of the facial nerve, including the variations among different ethnic groups, is essential to prevent an iatrogenic injury. The purpose of the study was to document topographic anatomy of temporal and marginal mandibular (MM) branches of the facial nerve in relation to temporomandibular joint (TMJ) surgery. The specific aim was to demonstrate detailed course of temporal and MM nerves, their surgical implications, and to compare the results obtained with the previous studies. METHODS: The investigators implemented a prospective cadaveric study. A dissection was carried out on 52 facial halves. The facial nerve was dissected according to the instructions described in the Cunningham's dissection manual. Anatomic landmarks were selected as determined by Al-Kayat and Bramley, and results obtained were compared with previous published articles. RESULTS: The study sample was composed of 52 facial halves (males, n = 35; females, n = 17). The number of branches of temporal nerve varied in dissected facial halves from 3 (n = 37 [70%]), 2 (n = 14 [26%]), to 1 (n = 1 [2%]). The distance between the lowest concavity of the bony external auditory meatus to the point at which the facial nerve bifurcates (distance B) was considerably less in the study population (1.79 cm) when compared with the reported literature (2.3 cm). There was no significant influence of gender and cephalic index on distances measured. There was 1 branch in 15% of the dissected facial halves (1 in 52) and 2 branches in 85% (44 of 52). The MM nerve was seen coursing below the inferior border of the mandible, and in 44 (85%), the nerve was present above the inferior border of mandible all along the course. CONCLUSIONS: The topographic anatomy of the temporal and MM nerves is the same as reported in the literature. The only considerable difference was found in distance B; hence, surgical procedures involving the distance B require special consideration.