The marginal mandibular nerve in relation to the inferior border of the mandible.

PURPOSE: Injury to the marginal mandibular nerve (MMN) can occur in numerous surgeries involving incisions near the inferior border of the mandible. Injury to this nerve can cause considerable cosmetic and functional deformities. A thorough knowledge and understanding of the anatomic pathway of the MMN is important to avoid permanent nerve damage. The purpose of this study was to determine the position of the marginal mandibular nerve in relation to several key mandibular anatomic landmarks and to identify variations of the nerve as it approaches the inferior border of the mandible. MATERIALS AND METHODS: Human cadavers were dissected superficially from the parotid gland to the mental protuberance to expose the MMN. At complete exposure of the nerve, 5 anatomic landmarks on the inferior border of the mandible were identified and labeled. The distance between the MMN and these landmarks was recorded, and the average measurements were used to approximate the most common pathway of the MMN. RESULTS: It was found that the MMN runs, on average, 0.75 mm below the gonion, 0.08 mm superior to the posterior border of the antegonial notch, 0.06 mm superior to the arc of the antegonial notch, 1.29 mm superior to the anterior border of the antegonial notch, 3.6 mm superior to the point at which the facial artery reaches the inferior border of the mandible, and 10.9 mm superior to the vertical line that extends from the commissure of lip to the inferior border of the mandible. CONCLUSION: These data suggest 3 general pathways of the MMN in relation to the inferior border of the mandible.