Defining the Cervical Line in Face-Lift Surgery: A Three-Dimensional Study of the Cervical and Marginal Mandibular Branches of the Facial Nerve

Background: Continuous sub–superficial musculoaponeurotic system (SMAS) dissection in the cheek with subplatysmal dissection in the neck is an important feature of many face-lift techniques, yet the neural anatomy in this area remains unclear, and recommendations regarding continuous dissection of these adjacent areas vary widely. The purpose of this study was to define the vulnerability of the facial nerve branches in this transitional area from the face-lift surgeon’s perspective and to specifically identify the location of the cervical branch penetration through the deep cervical fascia. Methods: Ten fresh and five preserved cadaveric facial halves were dissected under 4× loupe magnification. The skin was reflected, followed by elevation of a SMAS-platysma flap, with identification of the location of cervical branch penetration through the deep cervical fascia. The cervical and marginal mandibular branches were then dissected retrograde through the deep cervical fascia to the cervicofacial trunk to confirm identifications. Results: Cervical and marginal mandibular branch anatomy was found to be similar to that of the other facial nerve branches, all of which initially course deep to the deep fascia in their postparotid course. The emergence of the terminal branch or branches of the cervical branch through the deep cervical fascia was consistently at or distal to a line from a point 5 cm below the mandibular angle on the anterior border of the sternocleidomastoid muscle to the point where the facial vessels course over the mandibular border (cervical line). Conclusions: Continuous dissection of the SMAS in the cheek, with subplatysmal dissection in the neck crossing over the mandibular border, is possible without jeopardizing the marginal mandibular or cervical branches if done proximal to the cervical line. This study serves as the anatomical justification for continuous SMAS-platysma dissection, and has implications for all types of SMAS flap manipulations.