Facial Aging and Anatomy of the Facial Nerve

Facial aging is a consequence of the face’s unique adaptions for the mobility needed for facial expression. This chapter describes the soft tissue construct of the face as being in five concentric layers. Movement originates in the middle layer, which for the most part is muscular and closely bound to the overlying dermis. Stability is provided in key immobile areas around the orbital and oral cavities, by a system of facial retaining ligaments. The ligaments effectively bind the layers by attaching the dermis to the skeleton. While facial movement occurs primarily over the bony cavities, it also occurs adjacent to them in a series of soft tissue glide plane spaces. These sub-SMAS facial soft tissue spaces are located between the ligaments. Being areas that facilitate mobility, they are also areas of inherent weakness. This is where aging originates anatomically. The 3-dimensional course of the facial nerve after it exits the stylomastoid foramen and travels towards the muscles of facial expressions is related predictably and consistently with this five-layered anatomy, being initially deep to the deep fascia (layer 5) as it exits the parotid gland, transitions through layer 4 to innervate the muscle of facial expressions in layer 3. Understanding the transition of the facial nerve from deep to superficial is important as the are the locations where the nerves are susceptible to injury during sub-SMAS facelift procedures.