Anatomy and Physiology of theAging Neck

Scott Shadfar, MDa, Stephen W. Perkins, MDa,b,*

KEYWORDS

� Neck anatomy � Aging neck � Cervicomental angle � Platysma � Neck aesthetics � Cervicoplasty

KEY POINTS

� The skin’s ability to conform to the newly contoured neck shape depends on the skin’s inherentpliability and texture, and isoften related to its elastin andcollagencontent,whichdiminisheswith age.

� Thick-skinned and overweight patients should not expect dramatic, long-lasting results of theirneck contouring procedure because of gravitational forces and the weight of the tissues.

� The platysma courses inferolateral to superomedial, with 3 variations in patterns of interdigitation ordecussation in the midline submental region.

� Patients with minimal or no platysmal decussation can have interplatysmal fat in the submental re-gion herniate between the medial edges, which is contiguous with the deep subplatysmal fat,further contributing to the appearance of neck aging.

� Bone resorption at the level of the mentum, mandibular body, and mandibular angle contribute tothe clinical appearance of aging, with changes seen at the cervicomental angle as well as the overallsuperficial topography of the neck.

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INTRODUCTION

Neck rejuvenation and contouring procedurescontinue to expand and evolve, with a multitudeof techniques designed to address the clinicalconsequences related to aging. Patients presentwith concerns regarding the aged appearance oftheir neck, often caused by changes in skin quality,fat accumulation, muscle tone, sun damage, orchanges after weight gain or loss.1 The principalcontouring techniques in neck rejuvenation aredesigned to transform specific regions of theneck by reduction and/or relocation of volume,redundancy, or laxity.2 This article focuses on therespective anatomic levels of the neck, which al-lows a more systematic approach when evaluatingand treating patients with signs of neck aging.

Anatomy and Physiology by AnatomicStructure

Patterns of aging are variable. Those patients withthin necks, good skeletal support, and good neck

a Meridian Plastic Surgeons, 170 West 106th Street, Indigology—Head & Neck Surgery, Indiana University Schoo* Corresponding author. Meridian Plastic Surgeons, 170E-mail address: sperkins@meridianplastic.com

Facial Plast Surg Clin N Am 22 (2014) 161–170http://dx.doi.org/10.1016/j.fsc.2014.01.0091064-7406/14/$ – see front matter � 2014 Elsevier Inc. All

height age differently from those patients withheavy, short necks and poor mandibular support.3

The superficial topography of the neck also affectsthe perception of a youthful or aged neck. Theinterplay of the structures deep to the skin, andthe skin’s ability to drape over them, is what deter-mines this topography. These relationships have abearing on the patient’s final results when a sur-geon attempts to form an acute cervicomentalangle (CMA), shape a distinct inferior mandibularborder, or accentuate the anterior border of thesternocleidomastoid muscle (SCM), all of whichhave been thought to contribute to the attractive-ness of the neck (Fig. 1).1,3,4 In addition, theanatomic transition of the neck to the lower thirdof the face (neck-face interface) is fundamentalto the overall facial aesthetic. Classification sche-mas have been developed by several investigatorsto characterize the aging process of the face andneck.1,5,6 When assessing candidacy for possiblefacial and neck rejuvenation, the senior authoruses a 3-tier classification system, which focuses

anapolis, IN 46290, USA; b Department of Otolaryn-l of Medicine, Indianapolis, IN 46202, USAWest 106th Street, Indianapolis, IN 46290.

rights reserved. facialplastic.theclin

Fig. 1. (A, B) A youthful neck with an acute CMA, distinct inferior mandibular border, and visible anterior borderof the sternocleidomastoid muscle.

Shadfar & Perkins162

on skin laxity, submental lipoptosis, jowling, pla-tysmal banding, and the CMA.7

The neck can be separated into anterior and pos-terior triangles, and although the posterior neck canshowsignsof aging, this article focuseson theante-rior neck. The anterior triangles of the neck arebounded inferiorly by the sternal notch and clavi-cles, and laterally by the sternocleidomastoidmuscle (SCM) bilaterally. The trachea, thyroid, andcricoid cartilages represent the midline, dividingright from left. Posterior to the SCM demarcatesthe start of the posterior triangle, with the trapezius,occipital scalp, and cervical vertebrae forming theposterior boundaries. The superior aspect of theanterior neck is delineated by the chin and the lowermandibular line and angle, rising toward the mas-toid processes more posteriorly.3

Analyzing each layer from superficial to deep,therapies can then be tailored to specific anatomicstructures and relationships, further individualizinga patient’s treatment plan based on previouslyagreed-on goals and expectations.

SkinSkin changeswithin the neck can often be themostprominent feature seen with aging. Understanding

the anatomic and physiologic processes involvedwith skin aging is of great importance in formulatingindividual treatment algorithms.The sensory innervation of the anterolateral neck

skin is derived from the transverse cervical nerves(C2, C3, C4) as they sweep across the neck fromaround the lateral border of the SCM. The arterialblood supply of the superficial anterolateral neckis derived from branches of the subclavian arteries,as well as perforating branches from the externalcarotid arteries. The intermuscular and superficialfascias serve as the framework for the vesselscoursing to the skin. The external jugular vein andanterior communicating veins join the anterior jugu-lar system and travel underneath the platysma todrain the superficial neck structures.8

The skin acts as aprotective barrier that is contin-uously in contact with the environment, undergoingnot only chronologic aging but also photoaging as aconsequence of primarily sun-induced damagefromultraviolet irradiation.9 Sun-induced skin aging(photoaging), like chronologic aging, is a cumula-tive process. Both processes lead to the formationof reactive oxygen species and resultant damage tocellular components, including membranes, en-zymes, nucleic acids, and proteins, and disruption

Anatomy and Physiology of the Aging Neck 163

to the interactions between them.9,10 Additionalprocesses that result in the clinical appearance ofaging include shortening of chromosomal telo-meres, hormonal influences, as well as an age-associated decline in anabolic signaling moleculesand receptors, and upregulation of the reciprocalcatabolic factors.9,10 These cellular perturbationsmanifest clinically as xerosis, laxity, wrinkles,droopiness, loss of hair, and loss of color fromme-lanocyte depletion and decreased tyrosinase ac-tivity.10 Poikiloderma of Civatte is a commondermatologic condition seen in aging female pa-tients that can cause cosmetic imperfections inthe skin of the neck and chest. Often difficult toclear clinically, patients can show atrophy, pigmen-tary changes, as well as telangiectasia formation.11

On histology, epidermal senescence primarilyresults in a decrease in the number of melanocytesand Langerhans cells. In contrast, most clinicalaging and histologic changes occur within thedermis, with hypocellularity and flattened dermoe-pidermal junction rete ridges. There is disintegra-tion of the dermal matrix leading to volume loss,as well as findings of fewer and looser collagen fi-bers and functional fibroblasts.10,12 A summariesof the histologic changes accompanying skin ag-ing is shown in Table 1.10

External factors, such as gravity, play a largerole in the clinical appearance of the aging neckwhen taken in combination with the cellularchanges mentioned earlier. The constant force ofgravity exerts a mechanical pull on the alreadyunsupported and lax skin. This mechanical pullexposes the changes related to fat depletion,fat accumulation, or herniation, as well as thechanges related to loss of structural supportfrom the deeper structures as the skin hangs andfollows their contours.

The physiologic changes observed in skin agingaffect management. Regardless of the aging

Table 1Histologic features of aging human skin

Epidermis Dermis

Flattened dermoepidermal junction Atrophy (lo

Variable thickness Alteration otissue stru

Variable cell size and shape Fewer fibro

Occasional nuclear atypia Fewer mast

Fewer melanocytes Fewer blood

Fewer Langerhans cells Shortened cand abno

Adapted from Yaar M. Clinical and histological features of intBA, editors. Skin aging. Berlin: Springer; 2006. p. 9–21; with p

process, surgical considerations shouldbedirectedat redraping of the skin over the underlying neckstructures, which recreates the contour of theneck and CMA. The skin’s ability to conform to thenew shape depends on the skin’s inherent pliabilityand texture, and often is related to its elastin andcollagen content. In the setting of poor-quality orexcess skin, excisional techniques are often neces-sary to allow redraping of the skin.2,3

Good candidates for neck rejuvenation are pa-tients who have moderate thickness to their skin,with minimal sun damage, and who have retainedsome hereditary elasticity to the skin appropriatefor their chronologic age.7 However, some pa-tients with smooth and nonphotodamaged skinmay experience premature loss of skin elasticity,and may have an unsatisfactory duration of im-provement. In addition, thick-skinned and over-weight patients should not expect dramaticlong-lasting results of their neck contouring proce-dures (Fig. 2). The increased weight of the tissues,combined with gravitational forces, further limitsthe length of time in which the soft tissues remainfirm and in an upward vector.7

Cervical fasciaSuperficial cervical fascia The superficial cervicalfascia is a thin layer of connective tissue betweenthe dermis and the deep cervical fascia. This fas-cia covers the platysma muscle, as well as thecutaneous vessels, nerves, and lymphatics. A dis-tinguishing feature is that this layer contains fat,which leads some clinicians to consider it to be apart of the subcutaneous tissue, and not truefascia.13

Deep cervical fascia The deep cervical fascia canbe divided into 3 distinct layers with the superficial(investing) layer of the deep fascia covering thestructures deep to the platysma, including the

Appendages

ss of dermal volume) Depigmented hair

f connectivecture

Loss of hair

blasts Conversion of terminalto vellus hair

cells Abnormal nail plates

vessels Fewer glands

apillary loopsrmal nerve endings

—

rinsic versus extrinsic skin aging. In: Krutmann J, Gilchrestermission.

Fig. 2. (A, B) An aging neck with changes in the superficial topography (obtuse CMA, loss of a distinct inferiormandibular border, and anterior border of the SCM) with evidence of submental lipoptosis, platysmal banding,and skin laxity. Loss of the delineation of the neck-face interface is also noted with jowling and distinct melola-bial folds.

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strap musculature, SCM, and trapezius muscles.The submandibular compartments are also en-closed by this fascial layer. The middle or viscerallayer of the deep cervical fascia comes aroundto include the trachea, thyroid, and esophagus,whereas the deep layer envelopes the deep vas-cular (carotid, internal jugular vein) and neuralstructures of the neck, and includes the cervicalvertebrae and vertebral musculature. Fascial laxitycan occur, which is shown by changes in the su-perficial topography related to descent or expo-sure of the deep structures, includingsubplatysmal fat or ptosis of the submandibularglands.

Subcutaneous fatThe subcutaneous fat is found between the skinand the platysma muscle, and is also invested bythe superficial cervical fascia. Subcutaneous fatvaries in thickness according to the patient’sbody habitus and weight, and is often a presentingconcern for patients. There can be a variable distri-bution laterally along the surface of the platysma,with patients most often presenting with the

largest volume of fat anteromedially. Fat is usuallymost abundant in the submental area, forming atriangular shape with the apex at the hyoid andbase at the mandibular line. Often there is deepextension that is contiguous with the subplatysmalfat at the natural separation of the platysma mus-cles on their medial aspects.2 The amount ofdeep connection in this region depends on the de-gree of platysmal fibers decussating, which isvariable and is discussed later. This fat does nothave fibrous connections or septations, making itmore easily sculpted through closed or open pro-cedures including liposuction, as well as directexcision.3

Within the same subcutaneous plane, patientscan develop prominent melolabial folds or jowlsdescending from the face. Although they are notneck structures, their presence has a significantinfluence on the perception of a youthful andaesthetically pleasing neck.3 These structuresshould be considered in the preoperative analysisand in discussions with the patient, because theycan be concomitantly addressed during neck reju-venation. Most surgical alterations are targeted at

Fig. 3. Clear demonstration of the neck-face interfaceor junction of the SMAS (**) with the platysma (<>)after elevation and connection of facial and neck sub-cutaneous dissections.

Anatomy and Physiology of the Aging Neck 165

reducing the bulk of fat within this area, attemptingto develop a more acute CMA and establish anideal contour. Techniques such as submental lipo-suction or direct excision are the most commontechniques.

LymphaticsThe lymphatic drainage patterns within the neckare complex. Pan and colleagues,14 using lympho-scintigraphy, eloquently showed the lymphaticchannels within the anterior cervical region andisolated 2 distinct layers of lymphatic vessels.The more superficial anterior neck vessels coursebetween the dermis and the platysma, until ulti-mately penetrating the platysma medially to draininto the submental lymph node basin betweenthe inferior border of the mandible and the thyroidnotch.14 The channels seen draining to the sub-mandibular lymph nodes course from the areajust lateral to the platysma border. Deeper chan-nels between the platysma and the deep cervicalfascia can be identified draining into the anteriorjugular lymph nodes, as well as the supraclavicularlymph nodes.14

Superficial muscular aponeurotic systemWithin the face, deep to the subcutaneous fat andsuperficial fascia, is the superficial muscularaponeurotic system (SMAS). Skoog15 first pub-lished descriptions on subfascial rhytidectomy,with Mitz and Peyronie16 later outlining a distinctanatomic subfascial layer and labeling it as theSMAS.17 These descriptions have led to theadvancement and development of modern facelifttechniques, with substantial lasting improvementsestablished by addressing the SMAS layer as it re-lates to the neck and jawline as well.18 However,the literature shows significant differences ofopinion in the patterns of the SMAS architecturein relation to the face and neck.

In general, the SMAS is 1 continuous and orga-nized fibrous network within the face, contiguouswith the platysma muscle as it transitions fromthe face into the neck.19 The SMAS is a multidi-mensional structure consisting of collagen andelastic fibers, fat cells, and muscle fibers.19 Thesefibrous extensions course from the periosteum ormimetic musculature through the subcutaneouslayers connecting with the dermis. The complexattachments formed allow movement of all thelayers as a single unit during rhytidectomy, whichholds true for the SMAS junction with the platysmaat the neck-face interface (Fig. 3). The SMAS ex-tends over the parotid gland laterally, superficialand distinct from the parotidomasseteric fascia.Following the SMAS from lateral to medial thereis continuity with the zygomaticus major muscle

and levator labii superioris alaeque nasi muscle,but anteriorly the SMAS becomes thin and sparsein the cheek area.18 There is debate regarding therole of sub-SMAS dissection as a modality in treat-ing the prominent melolabial fold. Histologicstudies have shown that, within the medial aspectof the face, there is a zone of fusion among the or-bicularis oris, SMAS, and the buccinator muscle atthe level of the modiolus.18,20 During rhytidectomythe SMAS flap is pulled, and the resulting tensionis transmitted to the buccinator, orbicularis oris,and modiolus. This technique is associated witha pleasing result at the level of the melolabialfold, with a subsequent lateralization and elevationof the lower third of the melolabial fold and cornerof the mouth.18 Superiorly distinct layers exist be-tween the SMAS and the orbicularis oculi and thetemporoparietal fascia, but their discussion isbeyond the scope of this article.

Isolating the SMAS and dissecting within thesub-SMAS or deep plane has led to improvementsin managing the neck-face interface, midface, andmelolabial fold.6,18,21,22 Additional advantages ofthe deeper dissection, beyond of aesthetic resultsand longevity, are related to less subcutaneousdissection and risk of skin flap necrosis.23,24 How-ever, there are increased risks related to injuringbranches of the facial nerve when entering anddissecting within the sub-SMAS (deep) plane.

Aging of the neck secondary to significant jowl-ing, midface descent, and melolabial prominencesis common, and procedures addressing the SMASand the neck-face interface are more appropriate,rather than an isolated neck procedure, which islikely to lead to suboptimal results.2

PlatysmaThe platysma muscle is situated between the su-perficial and deep cervical fascia, and separatesthe subcutaneous fat from the deeper structures

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of the neck. The platysma originates from the su-perficial fascia overlying the superior aspect ofthe deltoid and pectoralis major muscle, with in-sertions at the mandible, depressor anguli oris, ri-sorius, and mentalis muscles superiorly. Theplatysma is contiguous with the SMAS into theface with innervation from the cervical branch ofthe facial nerve. The paired, thin muscles coursefrom inferolateral to superomedial, with a variableamount of interdigitation or decussation in themidline submental region. Cardoso de Castro25,26

further classified the patterns of decussation into3 types. In type I, which is present in 75% of thepopulation, there is limited decussation of theplatysmal fibers, extending only 1 to 2 cm belowthe mandibular symphysis. Type II is present in15% of the population, and has the platysmajoining completely from the mandibular symphysisthroughout the suprahyoid region, essentiallybehaving as a single muscle. Type III is the leastcommon and is present in 10% of patients, withno decussation of the platysmal fibers at themidline (Fig. 4).2,25,26

With aging, the platysma begins to lose tone andis pulled laterally, resulting in splaying of themedial fibers. In addition, there is attenuation ofthe deep retaining ligaments on the medial edgeof the muscle contributing to loss of tone. Thisloss of tone allows the medial edges to descend,leading to development of platysmal bands, whichcan be exaggerated with contraction. Patientswith minimal or no platysmal decussation canhave interplatysmal fat in the submental regionherniate between the medial edges, which iscontiguous with the subplatysmal fat of the deepcompartment, further contributing to the appear-ance of neck aging.1,2,26

Aging can result in laxity, redundancy, andbanding, which can be addressed with techniques

Fig. 4. Anatomic classification of platysmal muscle decussaIsolated management of the aging neck. Semin Plast Surg

such as submentoplasty or platysmaplasty. Thegoal is to resuspend and plicate the medial edges,and to excise redundant muscle and fat whennecessary.The deep compartment structures and sur-

rounding neurovascular anatomy are at risk oncethe plane deep to the platysma is breeched. Thisanatomy includes branches of the external carotidartery and the jugular venous system as well as thecervical and marginal mandibular nerve branchesof the facial nerve. The deeper neck compartmentis discussed in detail later.

Subplatysmal deep compartment structuresThe subplatysmal compartment (Fig. 5) definesthe deep plane in neck rejuvenation, and the surgi-cally relevant structures are discussed separatelywith specific neural and vascular structuresmentioned when pertinent to an anatomic region.

Subplatysmal fat With aging, there can be accu-mulation, depletion, as well as descent of thedeep subplatysmal fat. Herniation through the in-terplatysmal region further contributes to theappearance of submental fullness and an obtuseCMA.Thedeep fat can be broken down into the central,

medial, and lateral compartments, with Rohrich andPessa27 describing compartmentalization by colorvariations among the fat. The central compartmenthad a more discrete yellow color, whereas themedial and lateral compartments were pale, similarto buccal fat. The compartments cover the mylo-hyoidmuscles forming a triangular-shaped adiposetissuemass that extends from the lateral third of themandible to the thyroid cartilage.27

When excising fat or liposculpting in this area,the surgeon must exercise caution when resectingcentrally, because overaggressive resection mayresult in a hollow appearance to the neck. The

tion patterns. (From Mejia JD, Nahai FR, Nahai F, et al.2009;23(4):264–73; with permission.)

Fig. 5. Anatomic layers and structures of the superficial and deep neck. (From Ramirez OM. Advanced consider-ations determining procedure selection in cervicoplasty. Part one: anatomy and aesthetics. Clin Plast Surg2008;35(4):679–90, viii; with permission.)

Anatomy and Physiology of the Aging Neck 167

surgeon should always keep in mind that the idealappearance of the youthful neck maintains arounded contour as opposed to a more skeleton-ized appearance.4 Dissection in this region carriesa risk of injury to vascular structures, as well as thecervical and marginal mandibular branches ofthe facial nerve. In addition, the adipose tissue iswell vascularized, with several perforators joiningfrom the adjacent musculature. Vascularized level1A lymphatic nodes are also encountered duringsurgical dissection. Fat excision in this region re-quires bipolar cauterization in order to obtainhemostasis and avoid hematoma formation.

Digastric muscles The digastric muscles consist of3 distinct parts, with the anterior belly originatingfrom the mandibular fossa, and an interme-diate tendon attaching to the body of the hyoid,which then joins the anterior belly with the pos-terior belly originating from the mastoid notch.The digastric muscles form the boundaries of the

submandibular triangle. Separate nerves innervatethe muscle bellies, with the anterior belly beinginnervated by the mandibular division of the tri-geminal nerve via a branch of the nerve to themylohyoid. An additional branch to the digastricmuscle, slung from the facial nerve, innervatesthe posterior belly. The digastric muscles act toelevate the hyoid and also act as weak depressorsof the mandible.

The actions of the digastric muscles on the hy-oid are thought to contribute to formation of theCMA, and modifying the muscles for neck rejuve-nation and contouring has been under debate,with conflicting practices published.1,26,28 Sometechniques include plicating the muscles in themidline and shaving or excising hypertrophic com-ponents of the muscles, whereas others releasethe suprahyoid tendon aponeurosis connected tothe hyoid to deepen the CMA.1,3 The authors donot advocate maneuvers intended to augmentthe digastric muscles.

Shadfar & Perkins168

Submandibular glands The submandibular glandsare located within the submandibular triangle,which is formed by the digastric muscle bellieswith the inferior mandibular edge acting as the su-perior boundary. The glands are sheathed by theinvesting (superficial) layer of the deep cervical fas-cia. The mylohyoid muscle divides the gland intodeep and superficial sections, with the deep por-tions of the gland resting over the hyoglossusmus-cle. The glands primarily function in the productionof saliva, which additionally acts as a carrier fordigestive enzymes and immunologic factors.With aging, patients may develop ptosis or hy-

pertrophy of the glands, with both contributing tocontour irregularities in this region. Routine dissec-tion or excision of the glands is controversialbecause of the inherent risk to the surroundingstructures. The marginal mandibular nerve, lingualnerve, hypoglossal nerve, Wharton duct, facial ar-tery, and facial vein are all at riskwhenmanipulatingthe gland. In addition, neural injury, xerostomia,sialocele, or hematoma formation, possibly result-ing in airway compromise, are all complicationsthat surgeons should be aware of when counselingpatients regarding partial or total gland resection.Simply suspending the platysma or the fascia over-lying the glands to act as a sling can be advanta-geous in the treatment of ptotic glands withouttaking on substantial risk, and is the choice ofmost surgeons. The authors do not encouragethe manipulation of the submandibular glands inneck rejuvenation.

SCM The youthful neck is described as having adistinct outline of the anterior SCM border. Theanatomy of the SCM defines the lateral boundaryof the anterior triangle, which often is the extent ofdissection needed in neck rejuvenation. Themuscleoriginates at the manubrium sterni and medial one-third of the clavicle coursing posterosuperiorly toinsert on the mastoid process and lateral one-halfof the superior nuchal line. The superficial layer ofthe deep cervical fascia invests the SCM. Themus-cle is innervated by the spinal accessory nerve, andis involved in turning the head to the opposite side,as well as flexing the head.Running deep to the platysma and along the

lateral aspect of the SCM are the external jugularvein and great auricular nerve (discussed sepa-rately). The vein and nerve are separated fromthe SCM by the investing layer of the deep cervicalfascia. This separation becomes surgically rele-vant when dissecting posterolaterally, becausethe surgeon should transition to a plane superficialto the fascia of the SCM to ensure that the ele-vation does not pass deep to the fascia or theSCM. A plane of dissection deep to the fascia

could then allow injury to the external jugular veinand greater auricular nerve. The dissection is oftendifficult posteriorly because of the attenuation ofthe fat in this area and the stronger dermal attach-ments of the skin to the fascia and muscle.17,29

Great auricular nerve The great auricular nerve isformed by the second and third ventral primaryrami of the cervical plexus, and ascends alongthe SCM to innervate the lobule, the skin behindthe auricle, and skin overlying the parotid gland.The great auricular nerve is described as themost commonly injured nerve during rejuvenativeprocedures of the face and neck, which em-phasizes the necessity of having a thorough under-standing of its course to avoid injury. As describedearlier, it runs parallel to the external jugular vein,crossing the SCM at the junction of the superiorthird and lower two-thirds of the muscle. This re-gion is referred to as the Erb point, and the nervedivides approximately 6.0 to 6.5 cm inferior tothe external auditory meatus into its auricular,mastoid, and facial branches.1,3,30

The great auricular nerve can be preserved byexercising the precautions discussed earlier andmaintaining a plane of dissection superficial tothe fascia overlying the SCM.

Facial nerve The cervical and marginal mandibularnerves are the most frequently encounteredbranches of the facial nerve during deep dissec-tion within the neck. The cervical branch runs ante-roinferiorly from its emergence at the caudal end ofthe parotid, coursing under the platysma as it in-nervates the muscle. Disruption of this nerve canlead to lip depressor dysfunction; however, thisis rarely clinically relevant, and, if present, full re-covery is expected.31

The marginal mandibular nerve runs toward themandibular angle in a subplatysmal plane beforeturning across the body of the mandible to supplythe muscles of the lower lip and chin. The courseof the nerve has been described as passing 1.2 to1.3 cm, or less than 2 finger breadths, below thebody of the mandible, with multiple branchesencountered in most individuals.1,3,32 Owsley andAgarwal33 described anatomic danger zones forthe cervical and mandibular branches in a sub-platysmal plane. The zone is encompassed by theangle of themandible laterally, the oral commissuremedially, a line 1 cm above and parallel to the man-dibular border cephalically, and a line 2 cm belowthe mandibular border as the caudal boundary(Fig. 6).33 By maintaining deep dissection abovethe investing cervical fascia the surgeoncanprotectthe branches of the marginal mandibular nerve,with reports of injury ranging from0.5% to 2.6%du-ring rejuvenative procedures.3,33

Fig. 6. Dangerzonesof the facial nerve.Green indicatesa safe area, yellow indicateswhere cautious dissection isrequired, and red indicates where extreme caution isnecessary. (From Owsley JQ, Agarwal CA. Safely navi-gating around the facial nerve in three dimensions.Clin Plast Surg 2008;35(4):469–77, v; with permission.)

Anatomy and Physiology of the Aging Neck 169

Deeper structuresRoutine procedures for the aging neck do notcommonly violate the visceral (middle) layer or pre-vetebral (deep) layers of the deep cervical fascia.Further discussion regarding the cervical plexusoutflow, lower cranial nerves, internal jugularvein, and carotid artery are beyond the scope ofthis article. Such discussion is not pertinent toroutine procedures for neck rejuvenation.

Mandible As described earlier, the aestheticappearance and impression of youth can bestrongly influenced by the superficial topographyof the mandible. Ramirez3 describes severalmandibular landmarks as potential areas that high-light the aging process, including the lateral pro-jection and vertical length of the mandible; thedefinition and sharpness of the mandibular angleand inferior border; as well as the prominence,height, and width of the mentum. The aging neckcan be influenced by changes in mandibular con-tours seen with jowling, fat descent, submental full-ness, or bony atrophy. These changes all culminate

as loss ofmandibular definition,which carries impli-cations for the superficial topography of the neck,and potentially for the CMA. In addition, a recessedor atrophic mandible alters the point of transitionfrom the horizontal submental plane to the verticalplane of the neck and affects the CMA. Mandibularaugmentation can consequently have a seriousimpact on the appearance and harmony of theneck and face, as described earlier as the neck-face interface.

Hyoid The hyoid and its relationship to the above-mentioned muscular, bony, and fascial attach-ments take on a critical role in establishing theCMA. The hyoid bone typically lies at the level ofthe third cervical vertebrae and this position rela-tive to the mandible corresponds with the CMA.1

A low anterior hyoid results in the appearanceof an obtuse CMA, and the outcomes after reju-venation are often suboptimal because of itslow anatomic position. The ideal hyoid positionneeded to achieve an acute CMA is posteriorand superior. Surgical manipulation of the hyoidis not a routine practice in correction of the agingneck.

Cartilaginous structuresBelow the hyoid bone is the thyroid cartilage. Itsmost anterior projection, the laryngeal promi-nence, can be seen on inspection of the neck inmost men and in some female patients. This prom-inence was described by Ellenbogen and Karlin4

as a sign of a youthful neck; however, aggressivedissection in the neck can lead to skeletonizationof this structure and may result in unwantedmasculinization. The surgeon must be carefulwhen manipulating the structures overlying thiscompartment. Cartilaginous structures, such asthe cricoid or the superior and inferior horns ofthe thyroid cartilage, are not visible under mostcircumstances.

Radiographic imagingRadiographic imaging is not routinely performedin the clinical work-up of the aging neck. Inthe setting of previous trauma, or for patientswith a history of nonaesthetic surgical interventionin the cervical region, considerations for radio-graphic imaging may be given. Computed tomog-raphy or magnetic resonance imaging could beperformed for surgical planning. The authors donot customarily obtain imaging in the setting ofneck rejuvenation.

SUMMARY

There are a multitude of techniques designed toaddress the clinical consequences of aging within

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the neck. Neck rejuvenation and contouringprocedures are challenging and continually ad-vancing. Although the techniques are evolving,the anatomy is constant, and surgeons with afirm understanding of the anatomic relationshipswithin the neck are able to deliver consistent andaesthetically pleasing results for their patients.

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