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IntroductionIntroduction

• Surgeon should master surgical anatomy of the neck before embarking on any neck dissection

• Upper border of the neck: ant: FOM post: BOS

• Lower border: ant: upper border of 1st rib post: body of the 1st thoracic vertebrae

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Developmental AnatomyDevelopmental Anatomy

• Skin of the neck – from cervical dermatomes (2nd to 6th cervical segments)

• SCM, strap muscles and trapezius – cervical myotomes• Six branchial arches form at four weeks of POG – has principal

nerve and vessel• The first arch:

Form the upper border of the neck Bone: mandible - derived from Meckel’s cartilage Muscles: mylohyoid, ant. belly of digastric Trematic nerve is the mandibular branch of the trigeminal nerve The first pouch form ear structures only

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• The second arch: Bone: Styloid process, lesser cornu and upper body of hyoid bone - formed

from Reichart’s cartilage Muscles: platysma, post belly of digastric and stylohyoid Nerve: Facial nerve The second pouch – ear related structures

• The third arch: Bone: greater cornu and inferior body of the hyoid bone Cartilage: epiglottis – developed from hypobranchial eminence Muscle: stylopharyngeus Nerve: glossopharyngeal nerve The third pouch:

• ventral aspect – thymus• posterior aspect - inferior parathyroid gland

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• Arches four, five and six – merge to form one• The fifth arch being completely absorbed• The 3rd and 4th arches fuse forming cervical sinus• If persists cervical sinus (in lower neck, btw ICA & ECA to the

apex of the pyriform fossa

• Fourth and Six arches Cartilages: laryngeal cartilages Muscles: cricothyroid constrictors of the pharynx, intrinsic muscles of the

larynx Nerve: SLN, RLN (X) Fourth pouch: superior parathyroid gland Fifth pouch: ultimobranchial body Sixth pouch: intrinsic muscles of the larynx

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POUCH Overall Structure Specific Structures

1 tubotympanic recess tympanic membrane, tympanic cavity, mastoid antrum, auditory tube

2 intratonsillar cleft crypts of palatine tonsil, lymphatic nodules of palatine tonsil

3 inferior parathyroid gland, thymus gland

4 superior parathyroid gland, ultimobranchial body

5 becomes part of 4th pouch

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Triangles of the NeckTriangles of the Neck

• SCM divides the neck into anterior and posterior triangles• Triangles of the neck

Anterior: submental, submandibular, carotid and muscular Posterior: lateral neck, subclavian

Anterior triangle• Boundaries: SCM, inf. ramus of mandible, midline

• Submental: Boundaries: anterior belly of digastric, midline and hyoid bone Contains LN and submental salivary gland

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• Submandibular: Boundaries: Inferior margin of mandible, anterior and posterior bellies of

digastric Deep boundary – stylohyoid and mylohyoid muscle Contains: SM salivary gland, deep fascia, LN, ant. facial vein, facial artery,

MM br. of VII n.

• Carotid: Boundaries: ant. border of SCM, post belly of digastric, superior belly of

omohyoid Contains: upper carotid sheath, LNs

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• Muscular: Boundaries: lower anterior border of SCM, anterior belly of omohyoid, hyoid

bone, midline Contains: lower carotid sheath, infrahyoid strap muscles, upper

aerodigestive tract, thyroid and parathyroid gland

Posterior triangle• Divided into lateral neck, subclavian triangles

• Lateral Neck: Boundaries: Posterior border of SCM, ant border of trapezius, sup. border of

inf belly of omohyoid Contains: cervical plexus, fibrofatty tissue, LN, XI nerve

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• Sublavian: Boundaries: Lower border of Inf. belly of omohyoid, clavicle, post. border of

SCM Contains: fibrofatty tissue, scalene muscles, brachial plexus, subclavian

vessels, thyrocervical trunk, Sibson’s subpleural fascia and the pleura Trapezius muscle

• covers cervico-occiptal region• represents the posterior neck• rarely involved in detail

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Fascial LayersFascial Layers

• Superfical• Deep: investing layer, middle of visceral layer, deep layer

Superficial• Invests platysma muscle• Closely associated with adipose tissue• Penetrated by the blood vessels that supply the neck skin• Subplatysmal flap: protects the blood supply to the skin

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Deep1. Investing layer

• Arises from the ligamentum nuchae and the spinous process of cervical vertebrae and invests the entire neck

• Splits to enlose the trapezius, omohyoid, SCM, strap muscles and the parotid gland

• Superior attachment: external occipital protruberance, superior nuchal line, mastoid tip an zygomatic arch

• The splitting of the facial layer around the parotid forms a deep layer which fuses with the fascia around the ICA

• Forms stylomandibular ligament• Anterior attachment: hyoid bone• Inferior attachment: acromium, clavicle, sternum

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2. Carotid sheath• Derived from the superficial layer of DCF medial to SCM• Contains 80% of the LN of the neck, carotid arteries, IJV, X nerve

3. Middle layer, or pretracheal of visceral layer• Derived from the superficial layer of DCF – passes deep to the strap

muscles and encircles the tracheal, thyroid and esophagus• Movement of the hyoid and strap muscles during swallowing elevates

the fascia

4. Deep layer (prevertebral fascia)• Arises from the ligamentum nuchae and the spinous process of the

cervical vertebrae• Splits to enclose the postvertebral muscles, passes laterally around

the scalene muscles and then forms a layer over the vertebrae• Forms the floor of the posterior triangles and allows the pharynx to

glide during deglutition

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Neck SpacesNeck Spaces

Submental Space• Midline spaces that lies between the anterior bellies of digastric

muscles

Submandibular Space• Superf boundary: submandibular gland, digastric muscle• Deep boundary: mylohyoid muscle• Communicates with FOM around the posterior border of mylohyoid

Peritonsillar Space• Between tonsil and superior constrictor• Communicates through the fibres of the superior constrictor with

retropharyngeal and parapharyngeal space

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Parapharyngeal Space• Inverted pyramidal shape• Top: BOS; Inferior: Greater cornu of hyoid bone• Medial: Sup constrictor; Lateral: Pterygoid muscles, mandible and

deep lobe of parotid gland• Divided by styloid process into pre- and poststyloid spaces• Prestyloid space contains ectopic salivary tissue• Poststyloid space contains carotid arteries, internal jugular vein CN

IX-XII, cervical sympathetic chain and lymph node

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Retropharyngeal Space• Sits between the two parapharyngeal spaces and is continuous

with both• Superiorly: Skull base• Anteriorly: musculature of pharynx• Posteriorly: prevertebral fascia• Contains only lymph node• Continues inferiorly behind esophagus then with posterior

mediastinum

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Pretracheal Space• Lies anterior and lateral to the thyroid cartilage and deep to strap

muscles• Contains Delphian node and communicates with the superior

mediastinum

Prevertebral Space• Potential Space• Lies btw cervical vertebrae and anterior longitudinal ligament

(posteriorly) and the prevertebral fascia (anteriorly)• Extends down to 3rd thoracic vertebrae where the fascia is bound

to the vertebrae• Infection in this space can rupture directly through into the

posterior mediastinum

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MusclesMuscles

Sternocleidomastoid muscle• Has two heads of origin; that are from manubrium of sternum and clavicle• The manubrial tendon is attached to the front of the bone below the jugular

notch• The clavicular head arises from the superior surface of the medial third of the

clavicle• It is attached by a tendon to lateral surface of the mastoid process and by a thin

aponeurosis to the lateral half of the superior nuchal line• Spinal accessory nerve enters the muscle and runs through the deep part of it

and emerged at the posterior border of the muscle• It is enclosed within the investing layer of deep cervical fascia• It is crossed superficially by the greater auricular nerve, transverse cervical

nerve and external jugular vein• Deep to the upper half of the muscle lies the cervical plexus• Deep to its lower part lies the carotid sheath and its contents

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• The blood supply is derived from the branches of the occipital and superior thyroid arteries

• Is Innervated by the spinal part of accessory nerve mostly C2 and C3• Contraction of one muscle tilts the head towards ipsilateral shoulder, and

rotates the head and neck to opposite side• Both muscles acting together from below draw the head forwards• The muscles can assists in raising the roof of the thorax in forced inspiration• Can be tested by turning the face to the opposite side against resistance

and the muscle palpated

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Trapezius muscle• Wide origin from the medial third of superior nuchal line,

ligamentum nuchae down to 7th cervical vertebrae and all the spinous process and interspinal ligaments down to 12th thoracic vertebrae

• Superior fibres insert into clavicle and acromium • Inferior fibres insert into the spine of the scapular• Action: to rotate the scapular so that the glenoid fossa points up• Paralysis is a common consequence damage to the accessory

nerve leading to malrotation of the scapular and traction on the branchial plexus

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Omohyoid muscle• It arises from the upper border of the scapula, and occasionally from the

superior transverse scapular ligament which crosses the scapular notch• Inferior belly inclines forward and slightly upward across the lower part of

the neck, being bound down to the clavicle by a fibrous expansion• Inferior belly passes behind the sternocleidomastoid, becomes tendinous

and changes its direction• Superior belly lies close to the lateral border of the sternohyoid and inserted

into the lower border of the body of the hyoid bone• The central tendon of this muscle is held in position by a fascial sling derived

from investing layer of deep cervical fascia and is prolonged down to be attached to the clavicle and first rib

• The superior belly is supplied by the superior root of the ansa cervicalis with the ansa supplies the inferior belly

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• The inferior belly of the omohyoid divides the posterior triangle of the neck into an upper or occipital triangle and a lower or subclavian triangle

• Its superior belly divides the anterior triangle into an upper or carotid triangle and a lower or muscular triangle

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Digastric muscles• Posterior belly arises from the digastic notch on the medial surface of the

base of the mastoid process• Posterior belly tapers down to the intermediate tendon, which is attached to

the junction to the body and the greater horn of the hyoid bone• The tendon is lubricated by a synovial sheath within the fibrous sling• Anterior belly lies on the inferior surface of mylohyoid• Anterior belly connects the intermediate tendon to the digastrics fossa on

the inner surface of the mandible• Posterior belly is supplied by facial nerve• Anterior belly is supplied by the nerve to mylohyoid• The actions of the muscles are to depress and retract the chin and to assist

the lateral pterygoid in opening of mouth

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Strap muscles• Comprises of sternohyoid, omohyoid, thyrohyoid and sternothyroid

muscles• Move larynx and depress the mandible• Supplied segmentally from C1, C2, C3 via the ansa cervicalis• Retracted to access the trachea and thyroid gland• Form the anterior boundaries of the neck level

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Cervical LymphaticsCervical Lymphatics

• Divided into superficial and deep• Superfical vessels perforate the cervical fascia and drain into the

deep• Deep vessels:

commonly found around blood vessels, nerves and muscles drain the mucosa of the mouth, OP, NP, larynx and hypopharynx group of nodes: submental, submandibular, jugular chain, posterior nodes

Submental• Situated in the midline, inferior to mandible and between anterior

bellies of digastric muscles• Drain the anterior floor of mouth

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Submandibular• Divided into six groups: preglandular, prevascular, retrovascular,

retroglandular, intraglandular and deep nodes• Can be described as those related to submandibular gland those

related to facial vessels• Cancers of FOM, tongue and buccal cavity metastasize more

commonly to the perivascular nodes - cleared in the neck dissection

Jugular chain• Closely associated with internal jugular vein• Upper jugular nodes: drain the posterior faucial region esp

palatine tonsil

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• Middle jugular nodes: Found between carotid bifurcation and the level at which omohyoid tendon

crosses IJV Drain larynx, midhypopharynx and upper thyroid gland

• Lower jugular nodes: Between tendon of omohyoid and down to the thoracic inlet Sometimes referred to as prescalene group of nodes Form an important confluence between the mediastinal node group, the

axillary group and the neck Neck nodes may appear secondary to disease outside the neck

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• Posterior nodes: Arranged into two groups:

• Along the accessory nerve: first echelon for nasopharynx• Along the thyrocervical vessels: second echelon for the areas drained

by the anterior neck nodes

Lymph node levels

• Level I Refers submental and submandibular nodes Drains the lip, oral cavity and tongue Subzone Ia: submental nodes; Drains ant FOM, lower lip, ventral tongue Subzone Ib: submandibular nodes; Drains other subsite in oral cavity

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• Level II Forms upper jugular group of nodes Drains the oropharynx, larynx, hypopharynx and parotid IIa: Lies anterior inferior to Cr. XI Iib: Lies posterosuperior Positive Iia disease mandates Iib dissection Elective dissection for laryngeal and hypopharyngeal malignancy can

exclude level Iib

• Level III Refers to middle jugular node Drains the larynx and pharynx

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• Level IV Refers to lower jugular group of nodes Drains the larynx and hypopharynx

• Level V Refers to posterior triangle group of nodes Drains the other lymphatic regions in the neck Level Va:

• Superior to inf belly of omohyoid• Contains the chain of nodes along the accessory nerve, which drain

the nasopharynx Level Vb:

• Inferior to inf belly of omohyoid• Contains nodes related to the thyrocervical trunk which drains the

thyroid gland

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• Level VI: Anterior or central group of nodes Paratracheal, perithyroidal, Delphian nodes

• Level VII: Corresponds to the superior mediastinal tissues

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Level Nodes Boundaries Possible primary

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SubmentalSubmandibular

Midline, body of hyoid, posterior belly digastric, body of mandible

Lower lip, floor of mouth, lower gum

Face, nose, PNS, oral cavity, submandibular gland

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Upper deep cervical- upper 1/3 of IJV- adjacent spinal accessory(= upper half of carotid triangle)

Skull base aboveCarotid bifurcation below (clinically – level of

hyoid)Posterior belly digastric anteriorlySternomastoid posteriorly

Nasopharynx, Oropharynx, Hypopharynx, Supraglottic larynx, Oral cavity

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Middle deep cervical- middle 1/3 of IJV(=lower half of carotid triangle)

Carotid bifurcation aboveSuperior belly of omohyoid (clinically level of

cricothyroid notch) Sternomastoid posteriorly

Thyroid, Larynx, Hypopharynx, Cervical esophagus

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Lower deep cervical- lower 1/3 of IJV(= part of muscular triangle behind carotid sheath)

Superior belly of omohyoid above (clinically cricothyroid notch)

Clavicle belowSternomastoid posteriorly? Carotid sheath anteriorly

Thyroid, esophagus, breast, lung, GI

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Posterior triangle- spinal accessory group- supraclavicular group

Sternomastoid anteriorlyTrapezius posteriorlyClavicle below

Occipital – scalp, external earSupraclavicular –

nasopharynx, thyroid, esophagus, lung, breast

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Anterior neck between carotid sheaths- prelaryngeal- pretracheal- paratracheal(=part of muscular triangle in front of carotid

sheath)

Midline anteriorlyCarotid sheath posteriorly?Sup. Belly of omohyoid above? Sternum below

Thyroid

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Major Blood VesselsMajor Blood Vessels

Common carotid artery• The common carotid artery on the left side arises from the arch of aorta, where it

lies in front of the subclavian artery up to the sternoclavicular joint• The common carotid artery on the right side arises from brachiocephalic trunk

where it bifurcates behind the sterno-clavicular joint• The common carotid artery gives off no branches proximal to its bifurcation• It lies within the medial part of carotid sheath, where the internal jugular vein lies

lateral to it and the vagus nerve deeply placed between the two vessels• The sympathetic trunk is behind the artery and outside the sheath, which is

overlapped superficially by the infrahyoid mucles and sternocleidomastoid• It usually bifurcates into the external and internal carotids at the level of the

upper border of the lamina of the thyroid cartilage (upper border of C4 vertebrae)

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• The terminal portion of the artery is often dilated into the carotid sinus, which includes the comancement of the internal carotid artery

• The surface marking of the common carotid artery is along a vertical line from the sternoclavicular joint to the level of the upper border of the thyroid gland

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External carotid artery• It lies against the side wall of the pharynx somewhat medial to the internal

carotid artery• It then ascends in front of the internal carotid deep to the posterior belly of

digastric and stylohyoid• It pierces the deep lamina of the parotid fascia and enters the gland• It divides within the gland behind the neck of the mandible into the maxillary

and superficial temporal arteries• It is separated from the internal carotid by deep part of the gland and its fascia,

styloid process and its continuation the styloid ligament, styloglossus and the ‘pharyngeal structures’

• The facial vein crosses the artery, with the hypoglossal nerve lying between• The surface marking is along a line of bifurcation of the common carotid

passing up behind the angle of mandible to a midpoint immediately in front of tragus of the ear

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Internal carotid artery• It arises at the bifurcation of the common carotid and continues upwards within

the carotid sheath• At its commencement is the carotid sinus where its contained baroreceptors

are supplied by the glossopharyngeal and vagus nerves• The carotid sinus contains baroreceptors which mediate blood pressure

impulses to medullary centres• The carotid body is a small structure from which it receives two or three small

glomic arteries• The carotid body’s cells are chemoreceptors concerned with respiratory

reflexes and are innervated by the glossopharyngeal and vagus nerves• It lies lateral to lateral to the external carotid at its origin, but soon passes up

posteriorly to a medial and deeper level

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• It has no branches in the neck• It passes straight up in the carotid sheath, beside the pharynx, to the carotid

canal in the base of the skull

Internal jugular vein• It emerges from the jugular bulb at the posterior compartment of the jugular

foramen• At first behind the internal carotid artery, it lies on the transverse process of the

atlas, crossed by the accessory nerve• It receives the inferior petrosal sinus as its first tributary just below the base of

skull• The vein passes down to gain lateral side of the internal carotid artery

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• The deep cervical lymph nodes are closely adjacent to the vein throughout its course

• Its posterior relations include the cervical plexus and the phrenic nerve• The thoracic duct crosses behind the left vein at the level of C7 vertebrae• The inferior root of the ansa cervicalis curls around its lateral border, to unite

with the superior root at the variable level in front of the vein• The terminal part of the vein lies deep to the triangular interval between the

sterna and clavicular heads of sternocleidomastoid• It joins the subclavian veinto form the brachiocephalic vein behind the sternal

end of clavicle• Its tributaries below the inferior petrosal sinus are pharyngeal, lingual, facial

and superior and middle thyroid veins• At its commencement and termination of the vein slightly dilated to from

superior and inferior bulb

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External jugular vein• Forms a variable superficial system of vein along with posterior EJV and AJV• Drains blood from the face and scalp• Enters the subclavian vein where there are valves at the entrance with a further

set of veins at 4 cm proximal

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NervesNerves

Marginal Mandibular br. of Cr. VII• Runs inferior to the angle of mandible• Dips down into the neck and runs superficial to the submandibular triangle• Runs just deep to platysma and superficial to the deep fascia• Runs inferior to the greater cornu of the hyoid bone• Curves upwards and crosses mandible for a second time to the facial artery and

vein• Supplies depressor anguli oris, risorius, muscles of the lower lip

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Glossopharyngeal nerve• Trematic nerve of the third pharyngeal arch• Exits the skull at the anterior compartment of the jugular foramen• Has an inferior ganglion in the neck – contains cell bodies of the

sensory fibres• Passes down on the ICA then curves anteriorly around

stylopharyngeus, deep to hyoglossus and reaches the tongue• Branches:

Tympanic branch (Jacobson’s nerve)• Supplies sensation to the middle ear• Parasympathetic supply to the parotid gland via tympanic plexus

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Motor branch to stylopharyngeus Carotid sinus nerve: main supply to the carotid sinus and carotid body Pharyngeal branches: join the pharyngeal plexus on the middle constrictor

muscle Tonsillar branch: supplies the mucous membrane over the palatine tonsil Lingual branch:

• Supplies the posterior one-third of the tongue with sensory fibres and secretomotor fibres to the glands of the posterior third

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Vagus nerve• Trematic nerve for 4th branchial arch• Exits the skull base through the middle compartment of jugular

foramen• The nerve dilates to form the inferior ganglion beneath the skull

base• Below the ganglion, the vagus receives a branch from the

accessory nerve• Runs in the carotid sheath between the IJV and the ICA and CCA• Branches:

Auricular branch (arnold’s nerve): supply the TM and ear canal skin Carotid body branches: supplements the glossopharyngeal branch Pharyngeal branches: supply motor innervation to the constrictors and

soft palate

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Superior laryngeal branches:• Leaves the vagus high in the neck• Divides at the level of the hyoid into external and internal laryngeal

nerves Cardiac branches: Leave the vagus low in the neck and form the cardiac

plexus Recurrent laryngeal branches:

• Branches low in the neck• Left hooks around ligamentum arteriosum and arch of aorta and then

runs cranially in the tracheo-esophageal groove• Right runs along the subclavian artery before coursing medially towards

the tracheo-esophageal groove

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Spinal accessory nerve• Formed in the posterior cranial fossa by the union of spinal and cranial part• Emerges from the skull base through the middle compartment of the jugular

foramen, lateral to the vagus nerve• Cranial component joins the vagus just inferior to the inferior ganglion• Runs in contact with IJV, inf to the lateral mass of atlas and passes into the SCM• Supplies motor input only to SCM from C2 and C3 roots• Exits the SCM at the junction of the upper and middle thirds of the posterior

border• Runs across the posterior triangle btw the deep and superf layers of DCF• Enters trapezius at the junction of its lower and middle thirds

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Hypoglossal• Exits the skull through hypoglossal canal• Courses around the inferior vagal ganglion• Runs inferior around ICA then ECA to pass below the posterior belly of the

digastric• Runs around the stylomastoid branch of the occipital artery, ECA, lingual artery

and inferior to the greater horn of hyoid bone• It then courses upwards deep to hyoglossus and divides to supply all intrinsic

muscles of tongue and extrinsic muscle, except the palatoglossus• Gives the upper root of the ansa cervicalis

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Cervical plexus• Is formed by loops between the anterior rami of the upper four cervical nerves• Lies in the series with brachial plexus on the scalenus medius behind the

prevertebral fascia• It is covered by the upper part of sternocleidomastoid• Does not lie in the posterior triangle• The upper three cervical nerves have meningeal branches for the posterior

cranial fossa• The C1 fibres ascend with the hypoglossal nerve• The C2 and C3 fibres ascend thru the foramen magnum

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• Muscular branches of cervical plexus Are given off segmentally to prevertebral vessels (longus capitis, longus colli

and scalenes) The fibres from the branch of C1 are carried to superior root of ansa

cervicalis and nerves to thyrohyoid and geniohyoid Branches from C2 and C3 are to the sternocleidomastoid, while branches

from C3 and C4 are to the trapezius The inferior root of ansa cervicalis is formed by union of a branch each from

C2 and C3 The inferior root of ansa cervicalis descends to join the superior root (C1) at

the ansa

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• Cutaneous branches of cervical plexus Generally supply the front and sides of the neck and contribute to the supply

of the scalp, face and chest Lesser occipital nerve (C2) supplies posterior aspect of the upper neck

adjacent scalp behind the auricle as well as the auricle Transverse cervical nerve divides into ascending and descending branches

and innervate the skin of the front of neck from chin to the sternum Supraclavicular nerve emerges with the other three nerves at the posterior

border of sternocleidomastoid and soon divides into several branches Greater auricular nerve is a large trunk passing upwards over

sternocleidomastoid

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