Course of the masseteric nerve in masseter muscle.
The masseter muscle is often exploited by plastic and reconstructive surgeons in transposition operations to correct facial palsy. In benign masseteric hypertrophy, a neurectomy induces atrophy of the muscle and therefore a slender face. A clear understanding of the course of the masseteric nerve is essential in maneuvering the masseter muscle. Detailed dissection was performed on 48 head halves of Korean cadavers, and the inside of each masseter muscle was explored under the microscope with x10 magnification. The masseteric nerve ran anteriorly and inferiorly between the deep and the middle layers. The nerve was observed at 33+/-5.6 mm from the inferior border of the muscle on the anterior third vertical line of the masseter muscle and at 47+/-5.5 mm in the posterior third. The closest distance between the main nerve and the gonion was 32+/-4.1 mm. Approximately two thirds (69.6%) of the masseteric nerve intersected the artery. The safe limit is within 47 mm from the inferior border of the muscle on the posterior third vertical line and within radial 32 mm from the gonion.