Ebook Requisites in dermatology - Dermatologic surgery: Part 1

(BQ) Part 1 book Requisites in dermatology - Dermatologic surgery presents the following contents: Surgical anatomy of the head and neck, antisepsis, local anesthetics, surgical instruments, preoperative evaluation of the dermatologic surgery patient, cutaneous wound healing, electrosurgery, cryosurgery, biopsy techniques.

Edinburgh London New York Oxford Philadelphia St Louis Sydney Toronto 2009

Edited by

Allison T Vidimos, RPh, MD, FAAD, FACMS

Chair, Department of Dermatology

Cleveland Clinic Foundation

Cleveland, OH, USA

Christie T Ammirati,

MD, FAAD, FACMS

Associate Professor, Department of Dermatology Penn State Milton S Hershey Medical Center

Hershey, PA, USA

Christine Poblete-Lopez,

MD, FAAD, FACMS

Associate Staff, Department of Dermatology Cleveland Clinic Foundation

Cleveland, OH, USA

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First published 2009

ISBN: 978-0-7020-3049-9

British Library Cataloguing in Publication Data

A catalogue record for this book is available from the British Library

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A catalog record for this book is available from the Library of Congress

The Publisher

Printed in China

Acknowledgments

Dermatologic surgery dedications

We would like to thank our mentors and teachers

who have taught us the art and science of

dermatologic surgery, our residents, fellows and

medical students who have given us the privilege

and pleasure of teaching them, and our patients

who put their trust in us and challenge us to be

better physicians every day Special thanks go

to the the art and photography departments at Cleveland Clinic, especially Joe Pangrace, Bill Garriott, Beth Halasz, and our dermatology department photographer, Flora Williams

This text is dedicated to my parents Al and

Audrey Vidimos, my brothers Scott, David and

Dan, my husband Todd Stultz, and daughters

Katherine and Kristen for their love, support,

encouragement, and inspiration

Allison T Vidimos

This text is dedicated to my children Emma and

Nicholas and my parents Bob and Bee Travelute,

who inspired me to always reach higher, and to

my husband Chris, who held the ladder so I could

climb

Christie T Ammirati

This text is dedicated to my husband, Seevee, who has given me unconditional love and the support to pursue what I truly enjoy, most evident

in this endeavor; to my children, Veto, Samee, and Neo, who are the source of my strength and inspiration; to my parents, who taught me the value of education; to all my mentors, from whom I learned the art of surgical technique; and

to all the residents and fellows to whom I’ve tried

to teach the importance of this art

Christine Poblete-Lopez

Program Director, Dermatologic Surgery

and Cutaneous Oncology

Elizabeth Magill Billingsley, md

Associate Professor of Dermatology

Geisinger Health System Western Region

Geisinger Medical Group

State College, PA

T Minsue Chen, md

Fellow, Mohs Research in Advanced

Dermatologic Surgery Education

Mohs and Dermasurgery Unit

Department of Dermatology

University of Texas, M D Anderson Cancer

Center

Houston, TX

Theresa Dressler Conologue, do

Director, Cosmetic Dermatology ServiceGeisinger Medical Center

Danville, PA

Daihung Vu Do, md

Instructor in DermatologyAssociate Director of Dermatologic SurgeryDepartment of Dermatology

Beth Israel Deaconess Medical CenterBoston, MA

John Ebner, do

Department of DermatologyCleveland Clinic FoundationCleveland, OH

Gregory J Fulchiero Jr, md , MSBioEng

Dermatologic Surgery and Cutaneous Oncology

Lisa M Grandinetti, md

Department of DermatologyCleveland Clinic FoundationCleveland, OH

Joseph F Greco, md

Clinical InstructorUCLA Division of DermatologyDepartment of MedicineDavid Geffen School of Medicine at UCLALos Angeles, CA

Director of Dermatologic and Laser Surgery

Associate Professor of Dermatology, Surgery,

Otolarynogology – Head and Neck Surgery

Oregon Health and Science University

Cleveland Clinic Foundation

Assistant Professor of Molecular Medicine

Cleveland Clinic Lerner College of Medicine

of Case Western Reserve University

Cleveland, OH

Susan Teri McGillis, md

Director, Dermasurgery Center

Lancaster, PA

Jon G Meine, md

Staff, Department of Dermatology, Section

of Dermatologic Surgery and Cutaneous

Matthew R Ricks, md

LtCol, USAF, MC, SFSChief of Mohs SurgeryWilford Hall Medical CenterLackland AFB, TX

Christopher B Skvarka, md

Department of DermatologyHahnemann HospitalDrexel University College of MedicinePhiladelphia, PA

Aashish Taneja, md

Department of DermatologyWayne State UniversityDearborn, MI

Leonid Benjamin Trost, md

Department of DermatologyCleveland Clinic FoundationCleveland, OH

Allison T Vidimos, RPh , md

Chair, DermatologyCleveland Clinic FoundationCleveland, OH

Paula S Vogel, md

Col (Ret), USA, MCMohs SurgeonDermatology AssociatesSan Antonio, TX

Rungsima Wanitphakdeedecha, md

Department of DermatologyFaculty of Medicine Siriraj HospitalMahidol University

Bangkok, Thailand

Andrea Willey, md

Assistant Clinical ProfessorDepartment of DermatologyUniversity of California, DavisDavis, CA

Brittany Wilson, md

Department of DermatologyOregon Health and Science UniversityPortland, OR

Summer R Youker, md

Assistant Professor of DermatologySaint Louis University

St Louis, MO

Dermatology Requisites in

Also in the series

Dermatopathology

Dirk M Elston and Tammie Ferringer

Cosmetic Dermatology

Murad Alam, Hayes B Gladstone,

and Rebecca C Tung

Pediatric Dermatology

Howard B Pride, Albert C Yan,

and Andrea L Zaenglein

Dermatologic Surgery

Allison T Vidimos, Christie T Ammirati,

and Christine Poblete-Lopez

general Dermatology

Kathryn Schwarzenberger, Andrew E Werchniak, and Christine J Ko

Series foreword

The Requisites in Dermatology series of textbooks

is designed around the principle that learning

and retention are best accomplished when

the forest is clearly delineated from the trees

Topics are presented with an emphasis on the

key points essential for residents and practicing

clinicians Each text is designed to stand alone as

a reference or to be used as part of an integrated

teaching curriculum Many gifted physicians

This series of textbooks is dedicated to my wife Kathy and my children, Carly and Nate Thank you for your love, support and inspiration It is also dedicated to the residents and fellows it has been my privilege to teach and to the patients who have taught me so much

Dirk M Elston

Series dedication

have contributed their time and energy to create the sort of texts we wish we had had during our own training and each of the texts in the series

is accompanied by an innovative on-line module Each on-line module is designed to complement the text, providing lecture material not possible

in print format, including video and lectures with voice-over These books have been a labor of love for all involved We hope you enjoy them

This text is designed to cover the essentials of

dermatologic surgery in a style that is straight

forward and easily understood Each topic is

presented as a concise, yet thorough, review,

and each chapter is paired with an on-line

lecture In this manner, the text acts as an view for students learning the surgical aspects

over-of dermatology, a focused study guide for dermatology residents, and a ready reference for those in practice

Volume preface

Acknowledgments

Dermatologic surgery dedications

We would like to thank our mentors and teachers

who have taught us the art and science of

dermatologic surgery, our residents, fellows and

medical students who have given us the privilege

and pleasure of teaching them, and our patients

who put their trust in us and challenge us to be

better physicians every day Special thanks go

to the the art and photography departments at Cleveland Clinic, especially Joe Pangrace, Bill Garriott, Beth Halasz, and our dermatology department photographer, Flora Williams

This text is dedicated to my parents Al and

Audrey Vidimos, my brothers Scott, David and

Dan, my husband Todd Stultz, and daughters

Katherine and Kristen for their love, support,

encouragement, and inspiration

Allison T Vidimos

This text is dedicated to my children Emma and

Nicholas and my parents Bob and Bee Travelute,

who inspired me to always reach higher, and to

my husband Chris, who held the ladder so I could

climb

Christie T Ammirati

This text is dedicated to my husband, Seevee, who has given me unconditional love and the support to pursue what I truly enjoy, most evident

in this endeavor; to my children, Veto, Samee, and Neo, who are the source of my strength and inspiration; to my parents, who taught me the value of education; to all my mentors, from whom I learned the art of surgical technique; and

to all the residents and fellows to whom I’ve tried

to teach the importance of this art

Christine Poblete-Lopez

The essentials of dermatologic surgery must be

founded on a fundamental and thorough under­

standing of the head and neck anatomy This chapter

begins with an outline of important topographic

landmarks and cosmetic units before focusing on

the musculature, nerve anatomy, vasculature, and

lymphatics of the head and neck Special anato­

mic structures and regions such as the parotid

gland and scalp are addressed as well Emphasis

has been placed on the boundaries of anatomic

regions and danger zones as well as the spacial

relationships among clinically relevent structures

The important topographical landmarks of the

head and neck are formed primarily by underlying

bones and musculature, but superficial accepted

divisions are also made These landmarks and

divisions are important cosmetically and are used

in communication by the cutaneous surgeon

The scalp is divided into four areas – frontal,

parietal, temporal, and occipital The frontal scalp

extends from the forehead to the vertex and is

bordered by the parietal and temporal regions

The occipital scalp is located at the inferior por­

tion of the scalp, and overlies the occipital bone

The forehead meets the frontal scalp and extends

down to the eyebrows and glabella The glabella

lies between the eyebrows superior to the nasal

root Vertical furrows (glabellar lines) are accen­

tuated over this region when frowning

The frontal, maxillary, zygomatic, temporal,

and mandibular bones all form prominent bony

surface markers – the orbital rims, zygomatic

arch, mastoid process, and mental protuberance The orbital rim is formed by contributions from the frontal, zygomatic, and maxillary bones (Table 1­11) Of note, the medial canthal ligaments are easily palpated at the medial rim

Immediately above the superior orbital rim lies the first of the three major foramina that can

be found along a vertical, midpupillary line imag­ined approximately 2.5 cm lateral to the midline (Fig 1­1) The supraorbital, along with the infraorbital and mental foramina will be discussed further in the sensory innervation of the head and neck section

The prominence of the cheek or “cheekbone” is formed by the malar eminence of the zygomatic bone The buccal fat pad fills the area beneath this eminence and gives fullness to the cheek The zygomatic arch extends from the malar eminence towards the external acoustic meatus and is formed

by the temporal process of the zygomatic bone and the zygomatic process of the temporal bone The zygomatic arch also divides the temporal fossa superiorly from the infratemporal fossa inferiorly.The temple is a well defined danger zone where the temporal branch of the facial nerve and the superficial temporal artery and vein lie vulnerable

to injury (Table 1­22) The danger zones and areas

of susceptibility to injury are characterized later

in this chapter

The auricle is the entire visible portion of the external ear with many named processes (Fig 1­2) The rim of the auricle is known as the helix, which runs with a paired prominence, the antihelix The antihelix runs anterior to the helix and divides

Surgical anatomy of the

head and neck

Table 1-1 The orbital rim

Border BonesSuperior Frontal boneLateral Frontal process of zygomatic boneInferior Zygomatic bone laterally and maxillary bone

mediallyMedial Frontal bone superiorly and maxilla inferiorly

 Dermatologic Surgery

into two crura Between these crura, the named

triangular fossa appears The curved depression

between the helix and antihelix is referred to as

the scapha Inferior to the antihelix lies a deep

cavity known as the concha Anterior to the con­

cha, the tragus arises as an eminence in front of

the external acoustic meatus Opposite from the

tragus (separated by the intertragic notch) is a

small tubercle called the antitragus

Behind the ear lies the mastoid process of the

temporal bone It is a bony prominence that, after

adolescence, protects the facial nerve as it exits

the stylomastoid foramen Anterior to the ear lies

the condyle of the mandibular ramus, which can

be palpated as the mouth opens and closes The

angle of the jaw and prominence of the chin are

formed by the mandibular angle and mental pro­

tuberance, respectively

The masseter muscle attaches to the zygomatic

arch and inserts on the ramus of the mandible

It can be palpated most easily while the teeth

are clenched The facial artery may be found and palpated near the antero­inferior border of the masseter

The nasal bones, alar cartilages, and anterior nasal spine of the maxilla form the palpable bor­ders of the nose The nasal bones form the supe­rior root of the nose and the anterior nasal spine can be palpated at the root of the columella The labial area is bordered by the nose, medial cheek, and mental chin This area is separated from the cheek by the melolabial crease The upper lip

Temporal bone

2.5cm

Infraorbital foramen

Zygomatic archRamus of mandible

Angle of mandible

Body of mandible

Mental foramen

Mastoid process

Figure 1-1 Bony landmarks of the skull and foramina

Table 1-2 Borders of the temple

BorderInferior Zygomatic archAnterior Tail of the eyebrowSuperior Coronal suture linePosterior Temporal hairline

1

Surgical anatomy of the head and neck

is divided in half by the philtrum The philtrum is

a central linear depression bordered by two verti­

cal columns extending from the columella to the

vermillion border of the upper lip At this inferior

border, the columns help to create a contoured

double curve, resembling Cupid’s bow

Continuing inferiorly, the most important

superficial landmark of the neck is the sternoclei­

domastoid muscle When contracted, it is easily

palpated See Table 1­�� for a discussion of the

sternocleidomastoid muscle This muscle divides the neck into anterior and posterior triangles (see

Table 1­�� for information on the anterior triangle and Table 1­15 for the posterior triangle) The anterior triangle can be subdivided into the muscu­lar, carotid, digastric, and submental triangles

Of note, the spinal accessory nerve is suscep­tible to injury in the posterior triangle Injury results in paralysis of the sternocleidomastoid and trapezius muscles

ah antihelix

at antitragus

atn auriculotemporal nerve

c conchal bowl

cav cavum of conchal bowl

cym cymba of conchal bowl

ea external auditory meatus

The parotid gland is an anatomic landmark

deserving of special consideration It is a triangular­

shaped salivary gland nestled anterior to the auri­

cle within the borders of the zygomatic arch and

mandible (Fig 1­��, Table 1­55) It is anchored into

place by a fibrous fascial capsule contiguous with

the deep facia of the neck The substance of the

gland houses and protects the facial nerve as it

branches into a superior temporofacial and infe­

rior cervicofacial division The five well known

branches of the facial nerve originate from these

divisions prior to exiting the different poles of the

parotid gland (Table 1­��)

The parotid duct emerges from the gland at

its upper anterior pole and courses over the mas­

seter muscle and buccal fatpad (Fig 1­��) Here

it turns medially to pierce the buccinator muscle

and enters the oral mucosa opposite the second

upper molar (Fig 1­55) The duct runs approxi­

mately one fingerbreadth inferior to the zygomatic

arch, between the transverse facial artery and

buccal branch of the facial nerve With the jaw

clenched, the parotid duct may be palpated as a

firm cord along the middle third of a line drawn

from the earlobe to a point between the oral com­

missure and the nasal ala as it runs atop the mas­

seter The duct is most vulnerable in this location

during surgical procedures Transection will result

in extravasation of a clear watery fluid If left unrepaired, an external fistula may develop.Thin watery saliva and thicker mucous of the parotid gland mediated by sympathetic and para­sympathetic fibers respectively Cutaneous sen­sory innervation over the parotid gland is carried

by the auriculotemporal nerve Vascular supply and lymphatic drainage of the parotid area are described elsewhere in this chapter

Contour lines and cosmetic units

Key Points

• Contour lines separate the face into anatomic subunits

• Regional variablility in skin structure impacts the dermatologic surgeon’s choice of repair

• Free margins are a type of contour line

Contour lines are the natural lines of demarcation that divide the face into several cosmetic units, such as the forehead and nose (Table 1­��) Gen­erally speaking, the skin texture and color is con­sistent within each cosmetic unit and may vary considerably among them This is due in part to the differences in the density of sebaceous glands, terminal hair follicles, thickness and elasticity of the skin The highly thick and sebaceous skin of the nose, for example, lies in stark contrast to the neighboring thin and highly lax skin of the eyelid Defects in one cosmetic unit are therefore best repaired with skin of that same cosmetic unit The dermatologic surgeon must consider this regional variability during reconstructive surgery Surgical incisions may be placed so that the final scar lies along or parallel to contour lines Incisions that violate this principle by crossing the demarca­tion lines may distort anatomic units and result in highly perceptible scarring

Table 1-3 The sternocleidomastoid muscle

Origin Two heads – medial head attaches to the

sternum; lateral head attaches to the medial

third of the clavicle

Insertion Mastoid process of the temporal bone and

lateral portion of the superior nuchal line

Innervation Accessory nerve (cranial nerve XI)

Action Acting alone, a single sternocleidomastoid

muscle turns the head towards the ipsilateral

shoulder in an upward glance; in tandem, both

sternocleidomastoid muscles draw the head

forward

Comments The two originating heads of each

sternocleidomastoid muscle form a depression

referred to as the lesser supraclavicular fossa;

torticollis is due to the permanent contracture

of the sternocleidomastoid

Table 1-4 The anterior triangle

BoundaryAnterior Median line of neckPosterior Anterior border of sternocleidomastoid

muscleSuperior (base) Inferior border of mandibleRoof Skin, SMAS, platysma, and deep fascia

of neckFloor Inferior and middle pharyngeal constric­

tors; thyrohyoid and hyoglossus muscles (carotid triangle); mylohyoid and hyoglossus muscles (digastric triangle), mylohyoid muscle (submental triangle)

1

Surgical anatomy of the head and neck

Free margins are a unique type of anatomic

unit characterized by skin edges that are separated

from neighboring tissue by an open cavity Exam­

ples include the lips, eyelids, helical rims, nasal

alae, and columella Defects and repairs in close

proximity to free margins may have tension forces

that push or pull on the margin Distortion may

result in both aesthetic and functional impairment

such as eversion of the eyelid (ectropion) or lip (eclabion)

Cosmetic units may be further divided into subunits for anatomic classification This permits more precise localization of cutaneous neoplasms especially in patients presenting with numerous lesions

bfp buccal fat pad

fa facial artery

fv facial vein

ma masseter muscle

orb oc orbicularis oculi

orb or orbicularis oris

pd parotid duct

scm sternocleidomastoid muscle

sta superficial temporal artery

tfa transverse facial arter

zm zygomaticus major

Figure 1-3 Anatomy of the parotid gland and related structures

Table 1-5 Borders of the parotid gland

Superior Posterior two thirds of zygomatic arch

Posterior Posterior border of mandibular ramus

Inferior Angle of mandible

Anterior Highly variable

Floor Posterior half of masseter

Roof Integument, parotid fascia

Table 1-6 Facial nerve branches and the parotid gland

Facial nerve branch Exiting pole of the parotidTemporal (temporofacial division) Superior

Zygomatic (temporofacial division) AnterosuperiorBuccal (temporofacial division) AnteriorMarginal mandibular

(cervicofacial division) AnteroinferiorCervical (cervicofacial division) Inferior

to these musculofascial connections, the SMAS bonds to the skin via fibrous strands Collectively, this system augments and harmonizes facial movements, while acting as a screen to prevent the spread of infection from superficial to deep regions (Fig 1­��).

Knowledge of the SMAS aids the cutaneous surgeon in predicting the location of major neuro­vascular structures Arteries and sensory nerves of the face are found within the subcutaneous fat or

b buccal branch (VII)

bfp buccal fat pad

bz buccal/zygomatic nerve anastomoses

t temporal branch (VII)

tfa transverse facial artery

z zygomatic branch (VII)

zm zygomaticus major

Figure 1-4 Anatomy of the parotid duct and facial nerve

1

Surgical anatomy of the head and neck

at the SMAS–subcutaneous fat junction All mo­tor nerves course below the SMAS A sub­SMAS dissecting plane is attractive owing to its relatively avascular nature However, the risk to the motor nerves precludes use of the sub­SMAS plane in most locations The subcutaneous fat superficial

to the SMAS is therefore the ideal dissecting plane An exception occurs over the pre­parotid cheek where the motor fibers of the facial nerve lie protected within the substance of the parotid gland

Of note, the temporal branch of the facial nerve lies just deep to the thin superficial tem­poral fascia on the medial temple On the lateral temple, the auriculotemporal nerve and superficial temporal vessels are located in the subcutaneous fat above the superficial temporal fascia

an facial nerve anastomoses

b buccinator muscle

bfp buccal fat pad

dao depressor anguli oris

*parotid duct piercing buccinator muscle

*marginal mandibular nerve traveling with facial artery

Figure 1-5 Parotid duct as it pierces the buccinator muscle

Ta ble 1-7 Cosmetic units and contour lines

of the face

Contour line Cosmetic unit

�  Nasolabial fold �  Forehead

�  Nasofacial sulcus �  Nose

�  Mentolabial crease �  Cheek

�  Preauricular sulcus �  Eye

�  Eyelid margins �  Lip

�  Philtral columns/crest �  Chin

�  Alar contours �  Ear

�  Vermillion border

�  Eyebrows

�  Hairline

• Lines become more visible and deeper with ageand sun damage

• Knowledge of the skin tension lines is requiredfor successful cutaneous surgery and proper use

of cosmetic injectables

Tension, created by the intermittent contraction

of the muscles of facial expression, is transmit­ted by fibrous strands from the SMAS to the skin The elasticity of the skin with youth opposes this tension and maintains a smooth appearance With age, the elastic fibers decrease in their ability to resist tension, and collagen fibers elongate, decrease

in size, and become cross­linked With damaged collagen and elastin, linear wrinkles form along the attachments of the SMAS to the skin

* SMAS fibers connecting the underlying temporalis muscle to the skin

*

Figure 1-6 Superficial musculoaponeurotic system (SMAS)

Table 1-8 SMAS relationships

Region SMAS attachment site

Forms the galea aponeurotica to unite the

occipitofrontalis muscle; lacks muscle fibers

Forehead Envelops frontalis muscle

Temporal

scalp Continuous with the superficial temporal fascia

Zygomatic

arch SMAS is discontinuous above and below this insertion point; the actions of the upper

and lower muscles of facial expression are

functionally separated here

Cheek Deep leaflet of the SMAS fuses with the parotid

and masseteric fascia; envelops muscles of

1

Surgical anatomy of the head and neck

Generally these wrinkles, termed skin tension

lines (STLs), run perpendicular to the underlying

muscle fibers (Fig 1­��) For example, the STLs of

the forehead are horizontal because the frontalis

muscle contracts vertically The skin tension lines

of the lateral periocular skin (crow’s feet) radiate

away from the lateral canthus, as the fibers of the

orbicularis oculi circumferentially wrap from the

superior to inferior eyelid The horizontal wrinkles

of the upper eyelid, which at first seem to contra­

dict this principle, lie perpendicular to the axis of

the underlying levator palpebrae superioris

Surgical planning must include a thorough

knowledge of the STLs The reconstruction of sur­

gical defects should be designed to minimize per­

ceptible scarring One such way is to align the long

axis of a repair within or parallel to the STLs This

places the scar under the least amount of tension,

allowing the scar to fall within a natural wrinkle

Wounds close more easily in this orientation, as

the skin is approximately three times more disten­

sible perpendicular to the STLs than parallel

In elderly patients with severe sun damage,

the relaxed STLs will be obvious to any observer

However, certain techniques may be utilized to

accentuate these lines where the static wrinkles

may not be so noticeable Furrows can be accen­tuated by asking patients to perform exaggerated facial expressions, such as smiling, frowning, puckering lips, or whistling Active manipulation

of the skin by a gentle pinch or massage may also reproduce the natural folds and tension lines.STLs may be softened or eliminated by cos­metic injectable treatments Injectable botulinum toxin targets the dynamic STLs and moderately fine relaxed STLs by blunting the actions of the underlying musculature However, deeper relaxed STLs, accentuated by the gravitational pull of sun­damaged skin, are better treated by injectable fillers, which replace volume loss

The facial nerve and muscles

of facial expression

Key Points

• The muscles of facial expression develop from the second embryonic arch

• They contribute to the relaxed skin tension lines

of the face

• They are innervated by the seventh cranial nerve – the facial nerve

Figure 1-7 Skin tension lines

10 Dermatologic Surgery

The facial nerve, or cranial nerve VII, exits the

skull at the stylomastoid foramen and proceeds

to innervate the muscles of facial expression

(Fig 1­��) Immediately after exiting the foramen,

the posterior auricular branch breaks off the main

trunk to innervate the occipitalis and postauricular

muscles The remainder of the nerve pierces the

parotid gland and departs as five branches –

temporal, zygomatic, buccal, marginal mandi­

bular, and cervical (Fig 1­��) Each branch of the

nerve is discussed separately Table 1­�� highlights

the muscles innervated by each branch

During surgical procedures injury to a single

branch of the facial nerve is more likely to occur

than injury to the main trunk Conflicting reports

exist on the most common branch injured, as

the temporal, buccal, and marginal mandibular branches have all been implicated in different series Permanent injury to one of the branches

of the facial nerve is reported as 0.�–2.�%, with equal rates for subcutaneous and sub­SMAS procedures

The temporal branch is particularly vulnerable

to damage on the lateral face after exiting the superior pole of the parotid gland (Table 1­10, Fig 1­10) This branch runs deep to the skin, subcu­taneous tissue and a thin layer of fascia along its course to the frontails and orbicularis oculi mus­cles To prevent damage to this nerve, the surgeon should only dissect down to the superficial fat in this area Table 1­10 highlights other areas where the facial nerve is susceptible to injury

Facial artery

Parotid duct

Masseter muscle

Parotid glandMarginal mandibular branches

Facial nerve (CN-VII): main trunk

Temporofacial division of VIICervicofacial division of VIISuperficial temporal artery

Figure 1-8 Illustration of the facial nerve

1

Surgical anatomy of the head and neck

The zygomatic branch exits the anterosuperior

border of the parotid gland and divides into upper

and lower rami (see Figs 1­� & 1­�) Branches of

the lower ramus lie on the parotid duct Injury

to the zygomatic branch results in difficult clos­

ing the ipsilateral lower eyelid and can affect the

nasal muscles and lip elevators

The buccal branch exits the anterior border of

the parotid gland before coursing anteriorly over

the masseter muscle and buccal fat pad This

division runs parallel to the parotid duct prior to

delivering extensive rami to the mid­facial region

(see Figs 1­� & 1­�) Damage to this branch may

lead to the accumulation of food between the

teeth and buccal mucosa while chewing, as well

as drooling, impaired lip pursing, and impaired

smiling Injury to the zygomatic or buccal branch­

es is often temporary because of the high degree

of anastamoses between the two branches Some

�0–�0% of patients have these anastomoses

The marginal mandibular branch exits the infe­

rior pole of the parotid gland and travels along the lower angle of the mandible anterior to the facial artery (see Fig 1­��) Ramification occurs distally, near the muscles of the lower lip This renders the nerve vulnerable in its more proximal subplatys­mal location near the anterior insertion point of the masseter muscle on the mandible With injury

to this nerve, the lower lip becomes impaired in its downward movement, which can lead to an asymmetric smile

The cervical branch of the facial nerve exits

the inferior pole of the parotid gland and descends toward the submandibular triangle before ram­ifying extensively to innervate the platysma (see

Fig 1­��) Injury to this branch rarely causes noticeable damage

The extensive anastomotic network of the facial nerve, particularly via the zygomatic and buccal branches, may be predicted by dropping

dotted line damaged nerves anterior to it likely result in full recovery while

damaged nerves posterior to it likely result in permanent paralysis

dotted circle danger zone for fa and mm

Figure 1-9 Anatomy of the facial nerve

1 Dermatologic Surgery

an imaginary vertical line down from the lat­

eral canthus Branches anterior to this line have

extensive anastomoses, and injured nerves in this

“safe zone” will likely recover Damage posterior

to this line, however, often results in permanent

paralysis of the target musculature

Table 1­11 discusses each muscle of facial

expression separately See Figures 1­11 through

1­1� for the muscular anatomy of the face With

the exception of the buccinator, the muscles

of facial expression receive motor innervation

from their deep surface and thus protect their

terminal branches (Fig 1­1�) Of note, the levator

palpebrae superioris muscle elevates the upper

eyelid under the direction of the oculomotor

nerve (cranial nerve III) rather than the facial

nerve (Fig 1­15) See Boxes 1­1 through 1­� for the other functions of the facial nerve

Sensory innervation of the head and neck

The trigeminal nerve

Key Points

• The trigeminal nerve, cranial nerve V, is the largest of the 12 cranial nerves

• The three main branches are the ophthalmic (V1), maxillary (V2), and mandibular (V3)

• The trigeminal nerve provides the primary sensory innervation to the face

Table 1-10 Areas of the facial nerve susceptible to injury

Branch of facial nerve Danger zone descriptionFacial nerve

trunk as it exits the stylomastoid foramen

Behind the earlobe in children, the facial nerve trunk is vulnerable to injury

In adults, the trunk is protected by the mastoid process

Facial nerve in the parotid gland

Vulnerable to injury if the procedure breaches the fascia of the parotid glandTemporal branch Located between an imaginary line

drawn between the earlobe and the lateral eyebrow and a second line drawn between the earlobe and the most superior forehead crease It lies in its most superficial position as it crosses the zygomatic arch The facial nerve likely has multiple rami at this pointBuccal branch Lying superficial to the masseter muscle,

but deep to SMAS, this section is vulnerable at its branching points, 2 cm anterior to its exit of the parotid gland and under the modiolus (see below)Marginal

mandibular

This branch lies just below the fascia of the SMAS anterior to the facial vein and artery as it crosses the inferior edge of the mandible near the insertion point of the masseter

Table 1-9 Muscles innervated by the facial nerve

Branch of facial nerve Muscle innervated by branch

Temporal Frontalis

Corrugator superciliiOrbicularis oculi (upper portion)

AuricularZygomatic Orbicularis oculi (lower

portion)Nasalis (alar portion)Procerus

Buccinator

Depressor septi nasiNasalis (transverse portion)Zygomaticus major and minor

Levator labii superiorisLevator anguli orisRisoriusOrbicularis oris (upper portion)

Marginal mandibular Orbicularis oris (lower

portion)Depressor anguli orisDepressor labii inferiorisMentalis

Cervical Platysma

1

Surgical anatomy of the head and neck

The danger zone is predicted by drawing an imaginary line between the earlobe and the lateral eyebrow and a second line drawn between the earlobe and the most superior forehead crease The temporal branch of the facial nerve is vulnerable to injury as it courses over the zygomatic

arch within this zone

Figure 1-10 The facial nerve: danger zone

Table 1-11 The muscles of facial expression

Frontalis Raises eyebrows and

Part of the epicranius; the fibers of the frontalis are vertically oriented The horizontal forehead skin tension lines are created by this muscle If denervated, the eyebrow droops and skin tension lines relax on the damaged side

Corrugator supercilii Draws eyebrows

medially and downward Nasal bone Skin above middle eyebrow Creates the vertical glabellar frown lines

with the medial portion

of the orbicularis oculi and depressor superciliiOrbicularis oculi Eyelid closure

and upper eyelid depression; aids in tear excretion

Medial canthal tendon and nasal portion of frontal bone

Eyelid skin and surrounding musculature; lateral portion of orbicularis oculi is uninterrupted at the lateral canthus

Contraction forms folds that radiate from the lateral canthus (“crow’s feet”)

1 Dermatologic Surgery

Table 1-11 The muscles of facial expression—cont’d

Nasalis Compresses and

widens nasal aperture (“flares nostrils”) with deep inspiration

Maxilla lateral to nasal notch Nasal aponeurosis Major muscle of the nose

Levator labii

superioris alaque nasi Elevates ala and upper lip Superiorly at maxilla Alar cartilage and upper lip

Procerus Draws down medial

angle of eyebrow and produces horizontal wrinkles over nasal bridge

Nasal bones and cartilage Skin between eyebrows Temporary paralysis of this muscle helps

to reduce “bunny lines”; continuous with frontalis muscleBuccinator Compresses cheek

against teeth Maxilla and mandible Submucosa of cheek and orbicularis oris Muscular wall of cheek; if denervated, food

accumulates between teeth and cheek while chewing Pierced by parotid duct as it enters the mouth; receives motor innervation from its superficial surfaceZygomaticus major Upper lip elevator;

draws angle of mouth upward

Zygomatic bone Upper lip, angle of

mouth Important for smiling and laughingZygomaticus minor Upper lip elevator Zygomatic bone Orbicularis oris muscle Deepens nasolabial

sulcus during sadnessLevator labii

superioris Elevates and everts upper lip Maxilla and zygomatic bone Upper lip Provides a protective roof over the

infraorbital foramenLevator anguli oris Raises angle of mouth Maxilla Angle of mouth Contributes to depth of

nasolabial furrowRisorius Draws corner of mouth

laterally Zygomatic arch and parotid fascia Angle of mouth/modiolus Important for the smileOrbicularis oris Sphincter muscle

of lips for closing, pursing, protruding, or inflecting (prevents lip protrusion)

Maxilla, mandible, and modiolus (1 cm lateral

to corner of lips; fibers from orbicularis oris, lip elevators, and lip depressors converge to form a compact, mobile, fibromuscular mass called the modiolus)

Lips and vermillion border Modiolus contributes to cheek dimples

Depressor anguli oris Pulls angle of mouth

downward and laterally Mandible Angle of mouthDepressor labii

inferioris Draws lower lips downward as to convey

impatience, and may assist with eversion

Mandible and mental foramen Skin and mucosa of lower lip Contributes to expression of irony,

sorrow, melancholy, and doubtMentalis Raises skin of chin

and everts lower lip

to express doubt or

to pout

Mandible Skin of chin A wide space between

the two mentalis muscles can create a chin dimplePlatysma Depresses and wrinkles

skin of lower face and neck

Mandible Skin of neck and chest Most superficial

muscle of neck; overlies facial artery and vein, as well as marginal mandibular and cervical branches

of facial nerve

Occipital belly ofoccipitofrontalis

Posterior auricular

BuccinatorRisoriusOrbicularis oris

Figure 1-11 Muscles of facial expression

1 Dermatologic Surgery

of the trigeminal nerve, the ophthalmic (V1),

maxillary (V2), and mandibular (V�), carry sensa­

tion from distinct regions of the face (Fig 1­1�)

The regions are located anterior to an angled

coronal plane located at the vertex of the skull

Each main branch divides into smaller cutaneous

branches either before or after emerging from the

skull via bony foramina (the significant branches

are listed in Table 1­12)

The ophthalmic nerve (V1) is the smallest and

uppermost division, and further subdivides into

the nasociliary, frontal, and lacrimal nerves The

nasociliary nerve is the progenitor to the exter­

nal nasal branch of the anterior ethmoidal nerve

(which innervates the tip of the nose) and the ciliary nerve (which innervates the cornea) Her­petic invasion of the ophthalmic division present­ing with blistering on the nasal tip (Hutchinson’s sign) should alert the doctor to potential corneal involvement Zoster involvement of the external nasal nerve in one series indicated a ��% chance

of ocular involvement – double the chance if no lesions were present at the nasal tip

The frontal branch of the ophthalmic nerve gives rise to the supratrochlear and supraorbital nerves (Fig 1­1�) The supratrochlear nerve is the smaller of the two branches and runs 1 cm lateral to the midline, lying in the supratrochlear

an levator labii superioris alequae nasi (alar & labial)

fa facial artery

fv facial vein

lao levator anguli oris

lls levator labii superioris

orb orbicularis oculi

z zygomaticus minor

zma zygomaticus major

Figure 1-12 The cheek: anatomy of the infraorbital muscles

1

Surgical anatomy of the head and neck

notch of the orbital rim The supraorbital nerve

lies 2.5 cm lateral to the midline and exits via the

supraorbital foramen It is the largest extracranial

branch of the ophthalmic nerve Both branches of

the frontal nerve initially run deep to the frontalis

muscle At the mid­forehead, the medial branch

of the supraorbital nerve penetrates the frontalis

to run superficial to it

The maxillary branch (V2) divides into the

infraorbital, zygomaticofacial, and zygomatico­

temporal branches Of note, the infraorbital nerve

exits via the infraorbital foramen of the maxilla

(discussed below) and lies between the superior

heads of the levator labii superioris and levator

anguli oris (Fig 1­1�) The infraorbital division

innervates the medial cheek, upper lip, lower eye­

lid, lateral portion of the nose, and nasal ala

Two divisions (ophthalmic [V1] and maxil­

lary [V2]) of the trigeminal nerve provide sensory

fibers to the nose (Table 1­1�) In the trigeminal

trophic syndrome, injury to the maxillary division

(V2) results in a characteristic anesthetic ulceration of the nasal ala or alar crease This der­matomal insult of the trigeminal nerve may occur after surgical damage to the gasserian ganglion

or during postencephalitic states The nasal tip is spared in this syndrome, as it is innervated by the ophthalmic division (V1)

The mandibular branch (V�) is the largest division of the trigeminal nerve In addition to the sensory functions listed in Table 1­1�, it also provides motor fibers to the muscles of masti­cation (Box 1­��) Its main branches include the auriculotemporal, buccal, and inferior alveolar nerves The auriculotemporal nerve emerges on the face anterior to the tragus and crosses the root of the zygoma to accompany the superfi­cial temporal artery and vein to the scalp (see

Fig 1­22) The buccal nerve runs deep to the pa­rotid gland where it divides into many rami to innervate the skin over the buccinator muscle The terminal division of the inferior alveolar branch is the mental nerve, which exits to the skin at the mental foramen of the mandible (Fig 1­1�) See Table 1­1� for the cutaneous areas innervated by the branches of all three divisions mentioned

The trigeminal nerve also supplies postgangli­onic parasympathetic fibers to the lacrimal and parotid glands Frey’s syndrome, also known as auriculotemporal syndrome, is characterized by pain, hyperhidrosis, and vasodilatation of the cheek when eating (gustatory sweating) This syn­drome usually occurs after parotid gland surgery with injury to the auriculotemporal nerve Para­sympathetic fibers of the auriculotemporal nerve, normally carrying salivary stimuli, incorrectly reinnervate the sweat glands and blood vessels of the cheek Subsequent gustatory stimuli precipi­tate the above clinical features

The exit points, or bony foramina, of the supraorbital, infraorbital, and mental nerves are found in a vertically oriented, midpupillary line, 2.5 cm lateral to the midline This vertical line exists because of the predetermined embryol­ogy of each branch The supraorbital foramen lies slightly superior to the superior orbital rim The infraorbital foramen lies 1 cm inferior to the infe­rior orbital rim along the backslope of the maxil­lary bone The mental foramen is located on the lateral surface of the mandible toward the inferior edge of the ramus in the same midpupillary line

as the above Knowledge of these foramina allows the clinician to place anesthesia for effective nerve blocks

dao depressor anguli inferioris

dli depressor labii inferioris

lao levator anguli oris

lls levator labii superioris

1 Dermatologic Surgery

The supraorbital and supratrochlear nerve

block can be achieved with anesthetic placed

slightly superior to the superior orbital rim,

0.5–2.5 cm lateral to the midline Anesthetic

should be infiltrated deeply as both of these

nerves lie underneath the frontalis and corruga­

tor supercilii muscles at this location Blocking

the nerves will provide adequate anesthesia to

the ipsilateral forehead and frontal scalp Care

should be taken to avoid intraneural injection for

all nerve blocks Severe pain on injection reported

by the patient may indicate an intraneural loca­

tion This can be corrected by slightly retracting

the needle

Intraoral and percutaneous approaches can

be used for the infraorbital nerve block For the intraoral route, the needle is inserted into the superior labial sulcus with the surgeon’s thumb and index finger grasping the upper lip The needle is aimed toward the surgeon’s fourth finger overlying the infraorbital foramen (1 cm below the infraorbital rim) Some 1.0–1.5 mL

of anesthetic can be injected in this location The intraoral block offers less pain to the patient than the percutaneous route, and allows the needle to enter the tissue in the same plane as the infraorbital nerve For the percutaneous approach, the needle is aimed deeply toward

Shows the undersurface of the orbicularis oculi receiving terminal nerve fibers of the

zygomatic branch of the facial nerve

Figure 1-14 Orbicularis oculi muscle and the zygomatic branch of the facial nerve

dna dorsal nasal artery

mcl medial canthal ligament

soa supraorbital artery sof supraorbital foramen son supraorbital nerve

Figure 1-15 Levator palpebrae superioris (LPS)

B ox 1 - 1

Other muscles innervated by branches

of the facial nerve

• Stapedius

• Posterior belly of the digastric

• Stylohyoid

B ox 1 - 2

Areas innervated by sensory fibers

of the facial nerve

• External auditory meatus

Glands innervated by the facial nerve

with parasympathetic fibers

• Submaxillary

• Submandibular

• Lacrimal

0 Dermatologic Surgery

the same foramen through the skin of the cheek The anesthetic is injected slightly superficial to the foramen This block will provide anesthesia to the upper lip and areas summarized in Table 1­1�.The mental block can also be performed using intraoral and percutaneous approaches For the intraoral approach, the needle is advanced

in the inferior labial sulcus between the lower first and second premolars towards the fourth finger resting on the mental foramen During this insertion, the surgeon’s thumb and index finger grasp the lower lip Some 0.5–1 mL of anesthetic

is required for the mental block, producing anesthesia of the ipsilateral chin and lower lip

Marginal mandibular branch

Lesser occipital nerve(C2,3)

Great auricular nerve(C2,3)

Medial branches of dorsal rami of cervical spinal nerves

Branches from cervical plexus

Greater occipital nerve(C2)

Transverse cervical nerve (C2,3)Supraclavicular nerves(C3,4)

Auriculotemporal

nerve

Figure 1-16 Trigeminal nerve

Ta ble 1-12 Divisions and branches of the trigeminal

ZygomaticofacialZygomaticotemporalMandibular (V3) Auriculotemporal

BuccalInferior alveolar

1

Surgical anatomy of the head and neck

The cervical nerves and the

posterior triangle of the neck

The posterior triangle of the neck has definable

boundaries and contains critical motor and sen­

sory nerves (Table 1­15) Cutaneous branches of

the cervical plexus, along with the spinal acces­

sory nerve, course through the posterior triangle

of the neck in a region worthy of anatomic dis­

tinction Using an imaginary line drawn from the

angle of the jaw to the mastoid process, it may be localized approximately � cm inferior to the mid­point of this line at the posterior border of the sternocleidomastoid muscle (Figs 1­20 & 1­21) This neural­rich zone sits approximately at the level of the hyoid bone or the third cervical ver­tebra Alternatively, the region may be identified roughly as an area near the junction of the upper and middle thirds of the sternocleidomastoid muscle along its posterior border

Interestingly, this neural­rich zone has often and erroneously received distinction as “Erb’s point.” Dr Wilhelm Heinrich Erb (1��0–1�21),

a renowned German physician known widely for his prolific contributions to the field of neuro­logy, described and illustrated an area on the side

of the neck “from a circumscribed point, about two to three centimeters above the clavicle, somewhat outside of the posterior border of the sternomastoid and immediately in front of the transverse process of the sixth cervical vertebra.”

He termed this point “Erb’s point” or the “supra­clavicular point.” Erb noted that at this point,

stn supratrochlear nerve (yellow)

Figure 1-17 Medial forehead: supraorbital and supratrochlear neurovascular structures

 Dermatologic Surgery

“simultaneous contraction may be produced in

the deltoid, biceps, brachialis anticus, and supi­

nator longus muscles” through transcutaneous

electrical stimulation The neural­rich zone of

the cervical plexus within the posterior triangle

(approximately at the level of the third cervical

vertebra) thus lies superior to Erb’s point found

just above the clavicle (approximately at the level

of the sixth cervical vertebra) We shall refer to

the former as “pseudo­Erb’s point.” One motor

and four sensory nerves of the cervical plexus

emerge approximately 2 cm above or below

pseudo­Erb’s point along their course in and out

of the posterior triangle

The spinal accessory nerve (Table 1­1�) is a

cranial motor nerve that courses posteroinferiorly

through the posterior triangle of the neck Lying deep only to the skin and superficial cervical fascia, the nerve is vulnerable to injury during routine surgical procedures such as the punch biopsy

The cervical plexus lies deep to the sternoclei­domastoid muscle It is assembled from the ven­tral rami of the first four cervical nerves The most prominent peripheral branches that arise from this plexus are derived from the second through fourth (C2–C�) cervical nerves (Table 1­1�).The lesser occipital nerve (C2) emerges from behind the sternocleidomastoid muscle and runs parallel to its posterior edge to innervate the neck, mastoid area, and scalp posterior to the ear The great auricular nerves (C2 and C�) passes around the posterior border of the sternocleidomastoid muscle and ascends vertically towards the parotid gland and earlobe (Fig 1­22) The external jugular vein runs in close approximation to the great auricular nerves as they cross the superficial border of the sternocleidomastoid

The transverse cervical nerves (C2 and C�) sharply curve anteromedially upon exiting the posterior triangle, running between the external jugular vein and the sternocleidomastoid muscle

Table 1-13 Nerves that innervate the nose

Infraorbital nerve (V2) Mid­lower sidewall, ala

External nasal branch

of anterior ethmoidal

nerve (V1)

Nasal tip

Supratrochlear nerve (V1) Root, bridge, upper sidewall

Infratrochlear nerve (V1) Bridge, upper sidewall

a infraorbital artery

lao levator anguli oris

lls levator labii superioris (reflected)

n infraorbital nerve

z zygomaticus minor zma zygomaticus major

Figure 1-18 Infraorbital foramen and related structures

1

Surgical anatomy of the head and neck

Neither the great auricular nerve nor the

transverse cervical nerve supplies the skin of the

posterior triangle, as they leave the region quickly

The fourth branch of the cervical plexus, the

supraclavicular nerve (C� and C�), emerges from

pseudo­Erb’s point to innervate the skin of the

lower neck, clavicle, shoulder, and upper chest

For completeness, the posterior midline scalp is

innervated by the greater occipital nerve (C2) and

the third occipital nerve (C�) Neither develops

from the cervical plexus The platysma muscle

overlies and grants protection only to structures

at the inferomedial border of the posterior tri­

angle, such as the external jugular vein and the

transverse cervical nerve It is not a reliable struc­

ture that protects the major motor and sensory

nerves of this region

Sensory innervation of the ear

Key Points

• See Figure 1-22 for anatomic terms used to describe the features of the ear

• The innervation of the ear is supplied by the auriculotemporal nerve (a branch of the trigeminal nerve), great auricular nerve, and lesser occipital nerve (the latter two are branches

of the cervical plexus) (Table 1-18)

The ear can be described with a cranial surface (medial or closest to the scalp) and a lateral sur­face (visible surface in anatomic position) The auricle is the entire visible part of the external ear It is divided into cartilaginous and noncarti­laginous (lobule) domains

The great auricular nerve supplies the anterior and posterior portions of the ear lobule, inferior cranial surface, and posterior portion of the lateral surface (portions of the helix and antihelix) The lesser occipital nerve innervates the upper portion

of the cranial surface The auriculotemporal nerve supplies the majority of the lateral portion of the ear including the tragus and crus of the helix The conchal bowl is variably innervated by branches of the vagus and facial nerves

Arterial and venous supply

of the face

Key Points

• The facial blood supply is derived from the external and internal carotid arterial systems

• The facial artery runs with the marginal mandibular branch of the facial nerve near the masseter

• Most central facial blood vessels anastomose with their contralateral counterpart along the midline

• Dermatologists should be aware of multiple danger zones along the superficial face where named arteries may be injured during surgery

Ta ble 1-14 Regional sensory innervation

of the trigeminal nerve

Ophthalmic (V 1 )

Nasociliary Root of nose, medial

canthus, dorsum of nose, nasal tip, columella, a portion of upper eyelid, and cornea

Frontal (supratrochlear and

supraorbital branches) Medial upper eyelid and conjunctiva, forehead, and

frontal scalpLacrimal Lateral upper eyelid

Maxillary (V 2 )

Infraorbital Lower eyelid, medial cheek,

lateral portion of nose, nasal ala, and upper lipZygomaticofacial Malar eminence

Zygomaticotemporal Medial temple and

supratemporal scalpSuperior alveolar and

palatine

Upper teeth and gingiva, palate, and nasal mucosa

Mandibular (V 3 )

Auriculotemporal Lateral ear including

tragus, lateral temple, temporoparietal scalp, and temporomandibular joint

Buccal Cheek, buccal mucosa, and

gingivaInferior alveolar Mandibular teeth; lower

lip and chin (via mental nerve)

Lingual Anterior two thirds of

the tongue, floor

of the mouth, and lower gingiva

B ox 1 - 4

Muscles of mastication innervated

by the trigeminal nerve

 Dermatologic Surgery

The superficial arterial supply of the face encom­passes a vast network of vessels derived from both the external and internal carotid vascular systems (Fig 1­2�, Table 1­1�) The dual contribution and intricate anastomoses among each system create

a redundant blood supply that bathes the skin and underlying structures richly with oxygen and essential nutrients

The premiere facial branch of the external carotid system is the facial artery This principal vessel carves a tortuous path throughout its course over the superficial face, delivering multiple branches as described in Table 1­20 The facial artery debuts on the superficial face at the anteroin­ferior angle of the masseter muscle over the body

of the mandible (see Fig 1­��) Here the marginal mandibular branch of the facial nerve may be found along with the facial artery This potential

dao depressor anguli oris

dli depressor labii inferioris (transected)

Figure 1-19 Mental foramen and related structures

Table 1-15 The posterior triangle

Boundary

Anterior Posterior border of sternocleidomastoid

musclePosterior Anterior border of trapezius muscle

Inferior (base) Middle third of clavicle

Roof Skin, SMAS, platysma (variable), deep

fascia of neck (variable)Floor Splenius capitis, levator scapulae, and

scalene muscles

Contents

Motor nerves Spinal accessory (cranial nerve XI)

Sensory nerves Lesser occipital (C2), great auricular

(C2,C3), transverse cervical (C2,C3), supraclavicular (C3,C4)

1

Surgical anatomy of the head and neck

danger zone is protected by the overlying skin,

subcutaneous tissue, SMAS, and platysma Along

its course, the facial artery runs deep to the riso­

rius and zygomaticus muscles, anterior to the

buccinator, and variably anterior or posterior to

the levator labii superioris After the lateral nasal

branch splits from the facial artery near the nasal

ala, the terminal facial artery is known as the

angular artery (Fig 1­2�)

After the facial artery branches off, the external

carotid artery divides into two terminal branches –

the maxillary artery and the superficial temporal

artery The internal maxillary artery runs a deep

course within the head It contains four pertinent

branches that supply blood to the superficial face

(Table 1­21)

The superficial temporal artery (STA) arises

within the parotid gland and ascends superiorly

over the posterior aspect of the zygomatic proc­

ess It terminates by bifurcating into two divisions,

both of which enter the temporal fossa (Table

1­22) The STA courses along with, and anterior

to, the auriculotemporal nerve (see Fig 1­22)

The internal carotid system contributes to the

arterial supply of the superficial face through its

ophthalmic arterial branches (see Fig 1­1�, Table

1­2�) The internal and external carotid systems

unite superior to the medial canthal ligament where the dorsal nasal and angular artery anas­tomose Table 1­2� reviews the regional blood supply of the face

Peripheral pulses may be palpated over cer­tain anatomical regions of the face (Table 1­25) The superficial location of the vessels in these areas renders them susceptible to trauma dur­ing surgical procedures Physicians should always recognize these “danger zones” prior to any surgi­cal procedure in the area

Venous supply of the face

Key Points

• Veins of the face run parallel to the arteries

• Superficial regions of the face drain to the internal jugular venous system

• Deep regions of the face drain to the external jugular venous system

Figure 1­2� and Table 1­2� review the veins

of the face The supratrochlear and supraor­

bital veins unite to form the facial vein near the

medial canthus The facial vein runs posteroinfe­riorly and merges with the anterior branch of the retromandibular vein inferior to the mandible

Lesser occipital nerve

Spinal accessory nerve [XI]

Trapezius muscle

Supraclavicular nervesSternocleidomastoid muscle

Transverse cervical nerve

Great auricular nerve

Clavicle

Figure 1-20 Illustration of the posterior triangle of the neck

 Dermatologic Surgery

As the facial vein drains the majority of the face,

it travels posteriorly and superficial to the facial

artery The facial vein terminally drains into the

internal jugular vein.

Within the parotid gland, the superficial tem­

poral and maxillary veins unite to form the retro­

mandibular vein, which then descends between

the external carotid artery and the deeper positioned facial nerve The retromandibular vein bifurcates into an anterior branch (above) and

a posterior branch The posterior limb coalesces with the posterior auricular vein to form the

external jugular vein.

Veins of the face do not contain valves and are subject to potential retrograde flow The superior ophthalmic vein is contiguous proximally with the cavernous venous sinus of the dura mater covering the brain Distally, the superior ophthalmic vein connects with the angular vein Superficial midfa­cial thrombophlebitis with involvement of the fa­cial vein may result in retrograde flow of bacteria

to the dural venous system Care must be taken to avoid squeezing large pustules or furuncles of the midfacial region to avoid seeding the blood and dura with bacteria, given the above anatomy

ga great auricular nerve

lo lesser occipital nerve

san spinal accessory nerve

sc supraclavicular nerve

scm sternocleidomastoid muscle

tc transverse cervical nerve

tpz trapezius muscle

Figure 1-21 Anatomy of the posterior triangle of the neck (Erb’s point)

Table 1-16 Spinal accessory nerve

Innervation Trapezius and sternocleidomastoid (SCM)

musclesCourse Travels along a line connecting

junction of upper and middle third of sternocleidomastoid to junction of middle and lower third of trapezius

Damage Drooping of ipsilateral shoulder or

“winged scapula” (trapezius)Inability to raise and retract ipsilateral shoulder (trapezius)

Weakness in turning head to contralateral side against resistance (SCM)

1

Surgical anatomy of the head and neck

The lymphatic system

of the head and neck

Knowledge of the lymphatic drainage of the

head and neck is essential for evaluation of

malignancy and infection of the skin (Fig 1­2�)

The lymphatic system begins with fine lymphatic

capillaries in the superficial dermis that con­

nect with larger lymphatic vessels deeper in the

skin Unidirectional flow into lymph nodes and

lymphatic chains ultimately returns fluid to the

venous circulation at the junction of the internal

jugular and subclavian veins via the thoracic and

right lymphatic duct The clinically important

lymph nodes of the head and neck are listed in

Table 1­2�

The lymphatic drainage of the scalp and face

follows a predictable pattern (Table 1­2�), although

the drainage can be variable for each patient

The above groups of superficial collecting

lymph nodes ultimately drain to the superficial

and deep lateral cervical nodes The superficial

lateral cervical nodes lie above the sternocleido­

mastoid muscle and are associated with the

external jugular vein The deep lateral cervical

nodes run below the sternocleidomastoid muscle

with the internal jugular vein The deep cervical

nodes form a triangular pattern with the spinal

accessory, transverse cervical, and internal jugular

chains forming the superomedial, inferior base,

and superolateral arms respectively The internal jugular chain is the major collecting system of the head and neck See Table 1­�0 for the areas that drain to each chain

The anatomy of the scalp

Key Points

• The scalp is the soft tissue that covers the cranium and is made up of five layers

• The forehead and temple are components of the scalp, embryologically speaking

• Regions of the scalp include: frontal, temporal, parietal, occipital, vertex, and crown

• The vertex lies at top of the scalp anterior to the crown

• The galea aponeurotica is a component of the superficial musculoaponeurotic system (SMAS)

• Infection of the scalp can spread to the meninges via emissary veins

The layers of the scalp are summarized in Box 1­55

and Figure 1­2� using the mnemonic SCALP Its borders are delineated in Table 1­�1

The skin of the scalp contains many hair follicles and sebaceous glands that slice into the subcutane­ous fat A rich network of nerves and blood vessels traverses the connective tissue layer This second layer also contains thick fibrous bands (retinacula) that connect the skin to the galea aponeurotica and form the support network for the blood ves­sels When these vessels are cut, the thick bands hold the vessels open allowing the scalp to bleed profusely Consequently, undermining in this plane is suboptimal due to decreased visualization from excessive bleeding and significant resistance

to movement from retinacular attachments

The third layer of the scalp, the galea aponeu­rotica, contains two layers of fascia that encase and unite the bellies of the occipitofrontalis muscle through an intervening inelastic fascial membrane The galea is the strongest layer of the scalp, and wounds superficial to it do not spread Together with the skin, it functions as a unit that can move freely over the deeper layers As the frontalis and occipitalis muscles pull the scalp in opposite directions, incisions that interrupt the galea in a coronal plane increase the mobility of this inelas­tic membrane Cutaneous surgeons may exploit this tendency by making a small coronal incision,

or galeotomy, anterior or posterior to wound edges

to relax tension forces and permit easier closures.The loose areolar tissue of the scalp attaches the galea aponeurotica to the periosteum This relatively avascular layer provides the optimum site for undermining in the scalp Although the looseness of this space permits mobility of the skin and galea, it creates a potential space where large amounts of blood can collect after trauma

or surgery Posterior and posterolateral bony

Table 1-17 Sensory nerves of the cervical plexus

Nerve Spinal rami Cutaneous area supplied

Great auricular C2 and C3 Lateral neck, angle of jaw,

skin over parotid gland, anterior and posterior ear lobule, inferior cranial surface of ear, and posterior portion of lateral surface of ear

Lesser

occipital C2 Neck, mastoid area, and scalp posterior to the ear;

superior portion of cranial ear

Transverse

cervical

C2 and C3 Anterior neck

Supraclavicular C3 and C4 Lower neck, clavicle, and

shoulder

 Dermatologic Surgery

ejv external jugular vein

ga great auricular nerve

l ear lobule

pg parotid gland scm sternocleidomastoid muscle

Figure 1-22 Great auricular nerve and external jugular vein

1

Surgical anatomy of the head and neck

insertions of the scalp prevent the spread of fluid

or infection to the neck (Table 1­�2) Lateral

spread is contained at the zygomatic arch, the

insertion site for the temporal fascia However, as

no bony insertions exist over the anterior bound­ary, infection or blood from the scalp may track into the eyelids and root of the nose Infection

in loose areolar tissue can also spread to the meninges via emissary veins that pass directly to the dura (see below)

The final and deepest layer, the periosteum, is adherent to the bones of the cranium by connec­tive tissue fibers known as Sharpey’s fibers

The muscles of the scalp are summarized in

Table 1­��.The sensory innervation of the scalp is provid­

ed by six nerves, summarized in Table 1­�� When anesthetizing the scalp, the anesthetic should be placed superficial to the galea aponeurotica, as branches from these six nerves run in the connec­tive tissue layer

The arteries that supply the scalp navigate the connective tissue layer They are derived from both the internal and external carotid arteries (Table 1­�5) Rich bilateral anastomoses, in addition to the aforementioned retinacular attachments, explain why ligation of one end of a transected artery is insufficient to stop bleeding

Table 1-18 Sensory innervation of the ear

Nerve Anatomic location

Great auricular Majority of anterior and posterior

auricle: helix, antihelix, antitragus, entire lobule

Auriculotemporal Anterocranial auricle above external

auditory meatus: tragus, anterior crus and rim of helix, anterior half of external auditory canal

Lesser occipital Small segment of posterior auricle

and pre­mastoid skinFacial, vagus

Lateral nasal

artery and vein

Superior labial artery

Inferior labial artery

Facial artery and vein

Transverse facial

artery and vein

Occipital arteryOccipital vein

Posterior auricular artery

Posterior auricular vein

External jugular vein

Internal jugular veinExternal carotid artery

0 Dermatologic Surgery

Table 1-20 Facial artery branches (external carotid system)

Inferior labial

(Fig 1-25) Inferior to oral commissure Runs anterosuperior deep to depressor

anguli oris before penetrating orbicularis oris

Sandwiched between orbicularis oris and mucous membrane

as it travels along the margin of the lower lip

Labial glands, muscles, skin, and mucosa of lower lip

Has a septal branch

that runs superiorly along columella to

nasal tip and an alar

branch that runs superiorly towards nasal ala

Labial glands, muscles, skin, and mucosa of

upper lip, nasal septum

Skin of nasal alae, soft triangle, dorsum, and tip

Angular Terminal branch of

facial artery after lateral

nasal branch departs

Towards medial canthal ligament along nasal sidewall

Anastomoses with dorsal nasal artery

superior to medial

canthal ligament

Skin of cheek, elevators

of upper lip, orbicularis oculi, and nasal sidewall

Table 1-19 Pertinent facial arterial supply

Branches of external carotid artery (ECA) system Branches of internal carotid artery (ICA) system

Facial artery Ophthalmic artery branches

Internal maxillary artery

Superficial temporal artery

The veins of the scalp accompany the arter­

ies and are similarly named They anastomose

with the diploic veins of the cranial bones and

intracranial dural sinuses via emissary veins which

lack valves Subsequently, infection from the scalp

can spread in a retrograde flow to the meninges

via these valveless veins

Skin cancer on the scalp can metastasize to the lymph nodes of the head and neck The scalp anterior to the ears drains to the parotid, sub­mandibular, and deep cervical lymph nodes The posterior scalp is drained by the occipital and pos­terior auricular lymph nodes