Regardless of what technique of SMAS dissection is performed with facelift procedure, it is important to avoid injury to the facial nerve branches. Therefore, knowledge of the facial nerve anatomy is paramount. Davis et al. [3] described six different facial nerve patterns after 350 facial half dissections. These branches are susceptible to injury once they emerge from the anterior edge of the parotid gland. Several anatomic studies of the facial nerve have been performed to minimize the risk of injury of the structure with facial procedures. In the course of the facial nerve branches to their target muscles, there are three danger zones where these branches are susceptible to injury: the frontal branches, the marginal mandibular branches, and the midfacial branches.

Pitanguy et al. [5] described the frontal branch of the facial nerve as having a consistent course from 0.5 cm below the tragus to 1.5 cm above the lateral eyebrow. Ishikawa described the safe zone for prevention of injury to the frontal branch to be 4 cm above and 7 cm posterior to the lateral canthus. The frontal branch has also been found to have multiple rami in another cadaver study by Gosain et al. [6]. The most important anatomic study was performed by Stuzin et al. [7], who defined the location of the frontal branch in three-dimensional planes located on the undersurface of the temporoparietal fascia above the zygomatic arch. Therefore, when dissecting in the area cephalic to the zygomatic arch, it is critical to be subcutaneous to the superficial temporal fascia or deep to the superficial layer of the deep temporal fascia to avoid injuring the frontal branch.

The marginal mandibular branch was extensively studied by Dingman and Grabb [4] in 100 cadaver dissections. They found that, posterior to the facial artery, the marginal mandibular nerve passed above the inferior border of the mandible in 81% of their dissections. Anterior to the facial artery, 100% of the marginal branches were located superior to the inferior mandibular edge. Based on our observations, the facial artery is on average 3 cm anterior to the masseteric tuberosity along the mandible, or approximately one-fourth of the distance between the masseteric tuberosity and the mental midline.

In the midface, knowing the location of the anterior edge of the parotid gland, where the buccal and zygomatic branches exit, can minimize the risk of these midfacial branches. The sub-SMAS fat pad can also aid in identifying the location of the anterior edge of the parotid gland. If the SMAS is not freed just anterior to

the parotid, it does not move freely because of the resistance of the parotidocutaneous ligaments. Use of the masseteric tuberosity and the inferior lateral orbital rim as surface anatomic landmarks can predict the location of the anterior edge and facilitate safe release of the parotidocutaneous ligaments. In addition, our anatomic landmarks can provide the surgeon with the safe zone of the SMAS dissection, where the facial nerve is protected within the parotid gland and at minimal risk for injury.

35.6 Complications

35.6.1 Hematoma

As with any facelift procedure, bleeding is the most common complication. Blood pressure control is the single most important preventive measure. Other significant factors that can reduce the risk of bleeding and result in a safer procedure are avoidance of medications interfering with clotting or coagulation. Preoperative preparation and proper anesthesia can aid with preventing vomiting, coughing, pain, or any event resulting in a Valsalva-like maneuver.

35.6.2 Nerve Injury

The great auricular nerve is the most common symptomatic nerve injury after a facelift. Transection of this large sensory nerve can result in permanent numbness to the lower half of the ear and sometimes in a painful neuroma. A more dreaded complication is an inadvertent injury to a branch of the facial nerve. The buccal and zygomatic branches are injured more often than the frontal and marginal mandibular branches. Fortunately, the zygomatic and buccal branches interconnect freely superficial to the buccal fat pad. Consequently, the nerve palsy is usually less noticeable and paralysis is not permanent in most cases. Injury to these branches can cause the upper lip and oral commisure to sag.

Although, the frontal and marginal mandibular branches are less likely to be injured during a facelift, the clinical outcome of these injuries can be devastating. Paralysis of the frontal branch affects the forehead of the involved side with ptosis of the brow. The marginal