Locating the cervical motor branch of the facial nerve: anatomy and clinical application.

[BACKGROUND] Platysma innervation has various clinical applications. Although some patients have unsightly platysmal bands, others suffer from hyperkinetic motility disorders of the platysma that constitute both an aesthetic and functional impairment. Recently, the cervical motor branch has been used to reconstruct brachial plexus injuries. Dissection in this area can be precarious. The authors describe surface landmarks to help predict the location of the cervical motor branch of the facial nerve to more efficiently and safely operate in this area.

[METHODS] Sixteen fresh heminecks were dissected with the aid of loupe magnification. Measurements were taken to the branching point of the cervical nerve from the angle of the mandible and to a line from the mentum to the mastoid process.

[RESULTS] The cervical branch of the facial nerve was identified to branch below the mandible in all specimens. The branching point of the cervical nerve was consistently found in line with a perpendicular line from the angle of the mandible to the mastoid-mentum line. The branching point was located within 1.75 +/- 0.26 cm of this line. Dividing the mastoid-mentum line by the length of the ramus accurately predicted the distance from the angle of the mandible to the branching point.

[CONCLUSIONS] The cervical branch of the facial nerve can be reliably located within 1 cm below a perpendicular line from the angle of the mandible to a line drawn from the mentum to the mastoid process. Clinical applications of these findings range from cosmetic face-lift procedures to brachial plexus reconstructions.