Background: The marginal mandibular branch (Mbr) of the facial nerve is vulnerable to damage during rhytidoplasty, surgical reduction of the mandibular angle, parotidectomy, and excision of the submandibular gland. Objectives: The authors sought to map the Mbr and determine the relationship between the number of Mbr offshoots and the course of the Mbr. Methods: The Mbr was examined in 29 hemifaces from 12 embalmed and 4 fresh cadavers (10 males, 6 females; mean age, 73.7 years). Results: The Mbr was located ≤5 mm from the gonion (Go) in 24 of 29 hemifaces (82.8%) and ≤10 mm from the intersection of the facial artery and mandible (ie, FM) in 26 hemifaces (89.7%). In 16 hemifaces (55.2%), offshoots arose from the Mbr inferior to the mandible. The Mbr ran below the Go in 14 hemifaces (48.3%) and ran below FM in 13 hemifaces (44.8%). Except for minute offshoots deep to the platysma, the Mbr was not found to pass >2 cm below the mandible. The mean (± standard deviation) quantity of Mbr offshoots was 1.5 (± 0.6). A greater number of offshoots was associated with a higher likelihood of an inferiorly located nerve. The Mbr proceeded under the lower border of the mandible in 13 hemifaces (44.8%) and reached the mandible at a mean distance of 33.1±5.2 mm anterior to the Go. Conclusions: To avoid damaging the Mbr, surgical maneuvers should be positioned 4.5 cm anterior to the Go and 2 cm below the mandible.
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