Marginal mandibular nerve

Last revised by Daniel J Bell on 17 Apr 2022

The marginal mandibular nerve (TA: ramus marginalis mandibularis nervi facialis) is a branch of the extratemporal (terminal) segment of the facial nerve. It supplies the depressor anguli orisdepressor labii inferioris and mentalis muscles. It is of greater clinical importance than the other facial branches of the facial nerve due to its higher risk of surgical injury.

NB: do not confuse with mandibular nerve, major division of trigeminal nerve

  • location: lower face
  • origin and course: it is a terminal branch of the facial nerve
  • supply: depressor muscles of the lower lip/chin
  • relations: superficial to the inferior margin of mandible

The marginal mandibular nerve is usually single and arises as one of the terminal branches of the extratemporal segment of the facial nerve within the substance of the parotid gland. It then emerges from the parotid, in close proximity to the inferior margin of the mandible, passing directly superficial to it, superior or inferior to it. Interestingly, intraoperative studies show that the nerve tends to run just superior to the lower margin in the vast majority of patients; whereas cadaveric studies show a more variable course 4,5.

It then runs upwards, over the facial artery and vein, reaching the face just anterior to the anterior edge of the masseter muscle. As it passes forwards it runs beneath the platysma and then the depressor anguli oris muscles, passing over the submandibular gland as it does so.

The nerve has no named branches.

The marginal mandibular nerve supplies the depressor anguli orisdepressor labii inferioris and mentalis muscles.

Knowledge of the position of the marginal mandibular nerve is important for many head and neck surgeries, including parotidectomy, rhytidoplasty (face lift), and neck dissections, as due to its course, close to the inferior mandibular margin, it is easily damaged, and there is no consistent intercommunication between this nerve and any buccal branches (cf. other branches of the facial nerve). Iatrogenic trauma often results in devastating cosmetic results, due to paresis of the depressor muscles of the lower lip and angle of the mouth, and this may not be possible to correct satisfactorily. It is not an uncommon source of medicolegal action 1,5.

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