Facial nerve in rhytidoplasty: anatomic study of its trajectory in the overlying skin and the most common sites of injury.

The anatomic study of the facial nerve is closely related to the prevention of nerve injury that may occur in facial surgeries. The purpose of this study is to analyze the most susceptible areas in the face regarding the probability of facial nerve injury, based on the demarcation of its trajectory in the overlying skin. Three hundred cadaveric hemifaces were dissected (172 male, 128 female) and the facial nerve trajectory was followed from the stylomastoids foramen to the mimic muscles. The trajectory of the facial branches was delimited in the overlying skin by six diverging lines, with the following reference points: the upper and lower portions of the tragus, the most cranial wrinkle of the frontal region, the lower facial wrinkle of the frontal muscle, the nasal midpoint, an imaginary point 1 cm caudal to the oral commisura, another imaginary point also caudal to the oral commisura at the lower margin of mandible, and the clavicle midpoint. The temporal branches have the highest probability of being injured, followed by the mandibular marginal and buccal branches. The areas with greater risk of injury are the temporofrontal region (between the hairline and the lateral limit of the frontal muscle), the area near the angle of the mandible, and the preparotid region.