Topography of the Neck and Superficial Cervical Region

Outline

Pharynx at base of face, extends to C6 --> oesophagus
Neck viscera consists of pharynx, oesophagus, larynx and trachea; carotid sheaths on either side

Above larynx is hyoid; connected to mandible by myohyoid
CNs IX-XII enter neck.
Surrounding the neck is the deep cervical fascia, containing trapezius and SCM

Cervical cutaneous nerves (171)
From C2-4 nerves, on posterior surface of SCM

4 of them fan out to supply the neck
1. Lesser occipital nerve (C2) --> up and back post to ear
- supplies skin from auricle to occiptial region.
2. Great auricular nerve (C2,3) passes up immediately behind external jugular
- to supply auricle and preauricular region.
- gives posterior auricular nerve br. behind ear.
3. Transverse cervical nerve (C2,3), passes over  SCM
- to supply the anterior neck

4. Supraclavicular nerve (C3,4) passes down

- and divides into branches that pass over the vlacicle supplying the more lateral neck.

Cervical Fascia

Fascia is a relative term, some are convincing, others less so.

Superficial Fascia

Subcut tissue but includes platysma and fascial muscles in head and neck
Anterior and external jugular veins, and cervical cutaneous nerves lie in this.

Deep Cervical Fascia
Overstated; some have surgical significance

1. Investing layer (24 in 3rd)

Surrounds the neck like collar
- splits to invest both sides of SCM and trapezius and parotid / submandibular glands
- attached to hyoid bone
- attach along nuchal line to tip of mastoid
- blends with carotid sheath
- thickens at deep parotid to form stylomandibular ligament; deep lobe parotid tumours extend into a tunnel here; on eather side of the ligament 'dumb-bell tumours'; can distort soft palate
- lower attachment is to pectoral girdle; including sling around omohyoid.

2. Pre-vertebral fascia (68 in 3rd)
- membrane over prevertebral muscles
- floor of posterior triangle / floor of a radical neck dissection

Summary of Neck Triangles (23 in 3rd, 27-29)

Posterior

Boundaries: SCM, trapezius, clavicle

Contents: 4 arteries: occipital, transverse cervical, suprascapular, subclavian (29)

- 3 veins: transverse cervical, suprascapular and external jugular

- lots of nerves: accessory nerve, cervical plexus branches and brachial plexus trunks

- 1 muscle: omohyoid

- lymph nodes

Anterior

Boundaries: SCM, mandible, midline

Subdivided into: carotid, digastric, submental, muscular triangles (24)

Carotid

Boundaries: SCM, posterior digastric, superior omohyoid belly (most lateral strap)

Contents: arteries: bifurcation of common carotid, branches of external (except posterior auricular)

- veins: lingual, facial, superior thyroid

- nerves: hyoglossal, internal and external laryngeal, superior root of ansa cervicalis

- lymph nodes.

Digastric

Anterior body from midline of mandible (n to mylohyoid), back and down to intermediate tendon; 

Posterior body back and up to medial mastoid; (facial nerve)
Boundaries: Mandible, anterior and posterior bellies digastric

Contents: submandibular gland, lymph nodes, submental, facial and mylohyoid vessels.

- hypoglossal and mylohyoid nerves

Submental

Boundaries: anterior digastric belly, body of hyoid bone

Contents: anterior jugular veins, lymph nodes

Muscular

Boundaries: SCM, superior belly omohyoid, midline from hyoid bone to jugular notch

Contents: larynx, trachea, pharynx, oesophagus, thyroid, parathyroid (and their vessels & nerves), and lymph nodes

SCM (27)

 From front of manubrium and medial clavical
-> obliquely back to outer surface of mastoid and anterior part of superior nuchal line.
EJV courses across it from below the ear lobe to midpoint of clavicle; vein then plunges deep to join subclavian.

Great auricular nerve and transverse cervical emerge behind and travel across it
Parotid lower portion may lie on top of its upper extent

Lies over the carotids, IJV and deep cervical lymph nodes
Nerve Accessory; at deep surface 5cm from mastoid; emerges from posterior border constrant relation to great auricular nerve here  (erbs point)

- useful landmark for ID of nerve.
Pushes chin to one side against resistance --> tenses the opposite side.

Common incision for neck is at its anterior border

Infrahyoid Straps (27)
Sternohyoid and omohyoid = superficial
Sternothyroid and thyrohyoid = deep

Sternohyoid
- from back of manubrium coming medial (join in midline over thyroid) --> hyoid

Omohyoid
Superior belly inserts lateral to sternohyoid on hyoid, passes downwards
--> intermediate tendon behind SCM (suspended by a fascial condensation attached to clavicle)
Then passes to upper border of scapula near notch

Sternothyroid

From back of manubrium (inferior to sternohyoid) over thyroid to oblique line of thyroid cartilage
Thyrohyoid then arises from this line - basically a direct extension.
--> these muscles help in swallowing by depressing the larynx and hyoid.

Nerves: spinal nerves C1-3 via ansa cervicalis
Supplied high; above level of bottom of thyroid cartilage; best to divide straps midway between lower border of thyroid cartilage and suprasternal notch if need to.

Other cervical muscles

Scalenes
From transverse processes of first 6-7 cervical vertebra to first 2 ribs
Posterior and medial close together except posterior goes to 2nd rib
Middle largest and goes to first rib behind subclavian artery and brachial plexus
--> these separate it from the anerior scale (from C3-6), which inserts in first rib in front of sublavian artery but heind subclavian vein.
Lateral border of SCM approximates lateral border of scalenus anterior
- a pad of lympatic tissue lies between these muscles here; scalene node; usually FNA'd
Scalene nerve supply = branches of cervical nerve roots.
Phrenic nerve courses over top of scalenes from lateral to medial; thoracic duct lies on left at thoracic inlet

Ansa Cervicalis (65; 67 in 3rd)

Lies in front of internal jugular ® branches to infrahyoid muscles.

- usually imbedded in anterior sheath \ classed as a content.

Superior root = contains only C1 fibres, hitch-hike along XII.

- runs down on front of internal jugular --> branch to superior belly omohyoid

Inferior root = union of C2,C3 ant rami branches --> joins superior --> single nerve

- this forms a wide loop on lower IJV --> branches to sternohyoid, sternothyroid, inf omohyoid

- sometimes inferior root passes forward b/n IJV and ICA.