The soft-tissue layers of the face can be conceptualized as a series of concentric layers from superficial to deep (Fig. 101.1). These layers are the skin, subcutaneous tissues, superficial musculoaponeurotic system (SMAS), facial mimetic muscles, deep facial fascia, and bone. The main neurovascular structures lie just deep to the deep facial fascia and include the facial nerve, parotid duct, and facial vessels. This layer also contains the buccal fat pad. However, it is possible to damage the facial nerve intraoperatively when deep to SMAS and medial to the parotid, as the facial nerve becomes more superficial in this area, so care must be taken during sub-SMAS dissection. Retaining ligaments and fascial septa span across these layers to support the soft tissues of the face.1
The SMAS is part of the superficial fascial system of the face and neck, whereas the parotidomasseteric fascia is part of the deep fascial system of the face and neck. The SMAS is highly relevant to face-lift procedures and is often elevated and manipulated to support facial soft-tissue structures during rhytidectomy. It is continuous caudally with the platysma and superficial cervical fascia and cranially with the frontalis, galea, and superficial temporal fascia. At its most anterior extent, the SMAS forms the fascia around zygomaticus major, which can be a tethering point during a face lift requiring release. In contrast, the deep fascia which consists of the masseteric fascia, investing fascia of the parotid, deep temporal fascia, and deep cervical fascia, is not normally manipulated during face-lift procedures.1–4 Fig. 101.1 Facial soft-tissue layers. Skin Subcutaneous tissue Superficial facial fascia (temporoparietal fascia, SMAS) Deep facial fascia (parotidomas- seteric fascia) Parotid gland Temporal fascia Platysma muscle
The SMAS has both mobile and fixed components. The fixed SMAS overlies the parotid gland and is thickest in this region. The increased thickness at this site provides protection to the main facial nerve and its proximal branches. The mobile SMAS lies beyond the parotid (medially) over the facial mimetic muscles, facial nerves, and parotid duct. It is both thinner and more mobile than the fixed SMAS. This is clinically relevant to face-lifting techniques where the SMAS is mobilized around the parotid region and elevated in a posterior, oblique, or vertical direction. The SMAS is then secured in its new position to support the elevated soft tissues of the face and neck during the rhytidectomy. SMAS suspension can involve plication, imbrication, resection, or advancement techniques using sutures.1,2
4. Stuzin JM, Baker TJ, Gordon HL. The relationship of the superficial and deep facial fascias: relevance to rhytidectomy and aging. Plast Reconstr Surg 1992;89(3):441–449, discussion 450–451
The “malar fat pad” is a commonly used term referring to the region of the superficial cheek fat compartments that are thought to play a role in the appearance of the youthful cheek. With age, the malar fat pad loses volume and descends caudally, secondarily creating upper midface emptiness, lower-face fullness, and deepening of the nasolabial folds. The two primary components of the malar fat pad are the nasolabial and medial cheek fat compartments. The inferior orbital fat compartment can also be considered as part of this fat pad. It is separated from the other two components by cutaneous insertions of the zygomaticocutaneous ligaments. The facial fat compartments are divided into superficial and deep layers according to their relation to the SMAS and facial mimetic muscles. They are further described according to their anatomic subunit location, e.g., cheek, nasolabial, forehead, and orbit. There is a fairly even split between superficial and deep volume proportions in the cheek (54% compared to 46%, respectively). The superficial fat compartments of the cheek include the nasolabial, medial, middle, and lateral cheek fat compartments. The deep parts of the cheek are the buccal fat pad and the deep medial compartment. The superficial parts of the periorbital region are the superior, inferior, and lateral compartments. The deep compartments are the SOOF and the ROOF which are located beneath orbicularis oculi, not superficial to it. Of all the compartments in the face, the nasolabial one is unusual in that its volume remains fairly consistent through life. Fat located in the deep compartments seems to selectively age more than the superficial fat.1,2
The retaining ligaments of the face provide support for the facial soft tissues and are implicated in the facial aging process, either from attenuation or tethering. They originate from either bone or fascia and inset into the dermis. It is important to be familiar with them, as some of them must be released and/or repositioned during facial rejuvenation surgery, such as rhytidectomy and brow lift. They include the following: Ligaments that Cause Soft-Tissue Tethering • Mandibular ligament: Jowls and marionette lines (Fig. 101.3) Fig. 101.2 Anatomic layers of the temporal region. Skin Temporal fascia proper Frontal branch of facial nerve Parotid gland Path of dissection Continued path of dissection Variation Galea Deep layer of deep temporal fascia Superficial temporal fascia (temporoparietal fascia) (continuous with galea) Subcutaneous fat Periosteum Areolar (subgaleal) fascia (fuses with superficial fat pad) Superficial layer of deep temporal fascia Superficial fat pad Deep fat pad (buccal fat pad) Temporalis muscle Periosteum Zygomatic arch Parotid fascia SMAS Masseter muscle Ligaments that Attenuate Causing Soft-Tissue Ptosis • Orbitomalar ligament: Tear-trough deformity • Zygomaticocutaneous ligament: Tear-trough deformity and deepening of the nasolabial fold • Masseteric ligament: Formation of jowls and marionette lines 1–4
There are 23 paired muscles and the single orbicularis oris muscle involved in facial movement. They are grouped into four layers according to depth, not three. Those in layer 1 are the most superficial and include depressor anguli oris, zygomaticus minor, and orbicularis oculi. Those in layer 2 include depressor labii inferioris, risorius, and platysma. Those in layer 3 include orbicularis oris and levator labii superioris. Those in layer 4 include mentalis, levator anguli oris, and buccinator. All muscles are innervated by CN VII. A common examination question is which of the three represents the deep layer. The clinical relevance is that the nerve supply to these three is on their superficial surface rather than the deep surface which is the case with all muscles in the more superficial three layers.1,2
The vascular territory of the face and scalp is supplied primarily by the branches of the external carotid artery, with small contributions to the eyelid, brow, forehead, and scalp through the ophthalmic divisions of the internal carotid artery. The eight branches of the external carotid are: 1. Superior thyroid 2. Ascending pharyngeal Orbitomalar ligaments Zygomatic ligaments Fixed nasolabial sulcus Masseteric cutaneous ligaments Mandibular ligament Jowl Orbitomalar ligaments Zygomatic ligaments Masseteric cutaneous ligaments Jowl Fixed nasolabial sulcus Mandibular ligament Fig. 101.3 Changes in the aging face. 3. Lingual 4. Facial 5. Occipital 6. Posterior auricular 7. Maxillary 8. Superficial temporal The anterior facial arteries include the facial, labial, and supraorbital and supratrochlear vessels. The lateral facial arteries include the submental, zygomatico-orbital, and anterior auricular vessels. The scalp and forehead arteries are the superficial temporal, frontal, and temporal branches of the superficial temporal, posterior auricular, and occipital vessels. Facial vessels lie in the deepest plane with the parotid duct and buccal and zygomatic branches of the facial nerve. Blood supply to the anterior facial skin is through a dense network of myocutaneous perforators located along the oral commissures and nasolabial folds. The lateral facial skin is supplied by a network of sparsely populated fasciocutaneous perforators. Skin undermining during a face lift divides the fasciocutaneous perforators located laterally; thus, the blood supply of the facial flap is dependent on the medially based myocutaneous perforators. Many of the blood vessels that supply the face tend to travel in proximity to the retaining ligaments. For example, in the area of the zygomatic ligament, McGregor’s patch is known to contain a density of blood vessels that often bleed during dissection in that area.1–3
The great auricular nerve (C2–C3) lies on the sternocleidomastoid (SCM) muscle in the subplatysmal plane and is the most often recognized nerve injury after a face lift (6–7%).1 It is at greatest risk in its superficial location, which begins along the posterior border of the SCM muscle, 6.5 cm inferior to the tragus. This is known as McKinney’s point.2 Ozturk’s triangle is also a useful topographic marking for this nerve. The triangle is formed by a vertical line through the lobule perpendicular to Frankfurt’s horizontal line and then angles at 30 degrees posterior (Fig. 101.4).3 Division of the nerve or one of its key branches leads to numbness to the lower half of the ear including the lobule on both the medial and lateral surfaces. The lobular branch of the great auricular nerve is, as expected, the main branch responsible for sensation to the lobule. This branch courses within a defined area between vertical lines drawn between the tragus and antitragus (Fig. 101.5).4 30° Frankfurt’s horizontal line Fig. 101.4 Ozturk’s triangle. Lobular branch of great auricular nerve Fig. 101.5 Lobular branch of the great auricular nerve. The auriculotemporal nerve is a branch of the trigeminal nerve and courses with the superficial temporal artery. It may be inadvertently divided during a face lift. If the auriculotemporal nerve is divided, sympathetic reinnervation can occur, causing gustatory sweating (Frey’s syndrome). This is also a potential complication of parotid surgery. The lesser occipital nerve (C2–C3) travels over SCM muscle running between the muscle fascia and superficial fascia. It normally supplies the superior third of the ear and mastoid region. The zygomaticotemporal nerve is another branch of the trigeminal nerve that supplies sensation to a small area of skin in the temple. It is located lateral to the lateral canthus. It may be intentionally avulsed during migraine surgery but is not usually affected in face-lift surgery. The greater occipital nerve supplies the occiput and is also targeted in migraine surgery. It is decompressed rather than avulsed in this situation but is not at risk during face-lift surgery.
The facial nerve generally has five main branches. From cranial to caudal these are the frontal (or temporal), zygomatic, buccal, marginal mandibular, and cervical, respectively. Both the marginal mandibular and cervical branches are at risk of injury when the neck is undermined during a face or neck lift particularly when a subplatysmal dissection or muscle division is involved. Injury to either can have some similarity in clinical appearance. Essentially there will be some weakness of the lower lip with either, but there is a subtle difference in appearance and longevity of dysfunction. Damage to the marginal mandibular branch results in an inability to evert the lower lip, indicating depressor labii inferioris and depressor anguli oris paralysis. These two muscles pull the corners of the lip inferiorly and are supplied purely by the marginal mandibular branch in most cases. Therefore, patients struggle to pout (evert) the lips normally and may well have an asymmetric smile. The platysma is another lower lip depressor and is supplied by the cervical branches of the facial nerve on its deep surface. In some smile types (typically the full denture smile), the dysfunction of platysma after surgery can lead to new- onset obvious smile asymmetry without the lower lip eversion dysfunction. This is termed platysma pseudoparalysis. Patients typically recover completely from this injury within 6 months.1,2 It is thought to occur where there is division of platysma intraoperatively leading to division or stretching of some of the arborizing branches of the nerve. The frontal branch of the facial nerve is at risk during surgical procedures including face and brow lift. This can result in permanent weakness of the ipsilateral frontalis muscle and loss of brow elevation and rhytids on this side. One of the buccal branches is probably the most commonly injured motor nerve during a face lift, but given the arborization between buccal branches and zygomatic branches, this could often go unnoticed. Injury to one of the zygomatic branches is therefore similarly affected. This is most at risk of damage during an extended SMAS face lift due to its position deep and close to zygomaticus major. Avoidance of damage can be achieved by keeping dissection superficial to this muscle. Temporary weakness is suggestive of a neuropraxia or the effects of local anesthetic and most likely will resolve spontaneously. Ensuring the potential for motor nerve damage has been discussed with patients preoperatively is paramount, and should nerve injury be evident, regular additional office reviews will often be helpful and necessary to support them through the postoperative process.
The spinal accessory nerve (SAN) or CN XI supplies the SCM and trapezius muscles. It usually passes deep to or through the SCM in the anterior neck and is unlikely to be damaged there during a face lift. It is most at risk in the posterior triangle, passing between the SCM and trapezius, where it lies more superficially just beneath the skin. The anatomical landmark for this nerve has been described as Erb’s point which usually is the point at which it leaves SCM en route to trapezius. Erb’s point, however, is a term also used to describe the confluence of C5/C6 in the brachial plexus. The two points are distinct from one another. The SAN is purposefully dissected and preserved where possible during a neck dissection. In a face lift, it is often not seen. When there is injury to it, both SCM and trapezius muscles are affected leading to shoulder dysfunction, including depression of the shoulder girdle, scapular dyskinesis, muscle atrophy, difficulty initiating arm abduction, and some difficulty shrugging of the shoulders. Testing of the upper trapezius by asking the patient to shrug their shoulders alone, however, is unreliable because both the levator scapulae and rhomboid can provide this action. A useful clinical sign to confirm SAN dysfunction is the scapular flip sign. This is when the scapular lifts or flips from the thoracic wall during resisted glenohumeral external rotation. To perform this test, the examiner views the patient from behind and asks the patient to stand with the arm at the side and the elbow flexed to 90 degrees. The examiner resists external rotation at the distal forearm while observing the scapula position. In the presence of a SAN palsy, the unopposed pull of infraspinatus and posterior deltoid are believed to account for this finding.1,2 The hypoglossal nerve (CN VII) should not be encountered during a face lift but is seen during neck dissection. Damage to this would cause unilateral weakness of the tongue, as it supplies all of the intrinsic and extrinsic muscles except for the palatoglossus which receives vagal innervation. The facial nerve supplies the mimetic muscles of the face and the posterior belly of digastric muscle. The anterior belly is supplied by the trigeminal nerve (CN VIII) via the mylohyoid nerve of the inferior alveolar nerve. All of the facial nerve branches are at potential risk during face or neck lift surgery to a greater or lesser degree, depending on the technique employed.