Posterior Triangle of Neck & Deep Cervical Fascia😊

Posterior Triangle of Neck

• Levator Scapulae
• largest muscle in the floor of the posterior triangle

Contents

• Great auricular nerve

• Spinal accessory nerve

Great Auricular Nerve (GAN)

• Root value: C2–C3

• Runs with EJV

• Supplies:
• Ear lobule
• Skin at angle of mandible & parotid region

• Applied:
• Trigeminal nerve supplies face
• except angle of mandible → by GAN
• Parotid surgery injury → sensory loss in shaving area
• Auriculotemporal nerve injury → sensory loss in upper 2/3 auricle & temple

Frey’s Syndrome:

• Gustatory sweating.

• Parasympathetic fibers of Parotid gland (ATN)
• communicates with GAN (most common)

• Stimulus to ATN → sweating in parotid region

• Investigation: Starch iodine test.
• Sprinkle starch and Paint iodine

• ATN fuses with:
• Ettan (Atn) likes gan
• GAN > Buccal nerve > Lesser occipital nerve

• Mx:
• First line: Botox and anti-perspirants
• TOC: Tympanic neurectomy.

• Prevention: 
• SCM flap/digastric muscle flap to cover parotid bed.

Facial Synkinesis

• Facial nerve anomalous regeneration

• Examples
• Crocodile tears (Bogorad syndrome):
• Facial N Injury before geniculate ganglion.
• Fibers anastomose with chorda tympani.
• Lacrimation when patient eats.
• Mouth retraction on eye closure
• orbicularis oculi aberrantly innervate orbicularis oris

Spinal Accessory Nerve (SAN)

• Supplies: Sternocleidomastoid (SCM) & trapezius

• Course:
• Runs between investing layer & prevertebral layer
• Runs on levator scapulae
• Superficial to prevertebral fascia → higher injury risk in neck surgery

• Injury in posterior triangle:
• SCM spared
• Trapezius affected

• Trapezius muscle:
• Single = triangular shape
• Both = rhomboid shape

• Effects of trapezius injury:
• Difficulty in
• shoulder shrugging
• scapular retraction
• overhead abduction > 90°
• Shoulder drop

• Contents:



1. External Jugular Vein
2. Spinal Accessory N
3. + Nerves that exit through Erb's point:
• Lesser occipital nerve
• Great auricular nerve
• Transverse cervical nerve
• Supraclavicular nerve
• Mnemonic: Jaan (Son → GAN) → Loan (LON → Lesser occipital N) eduth TC (Transverse cervical N) vangi Schoolinn (Supraclavicular N)

Ansa Cervicalis

• Loop-like nerve structure

Formation

 

• Superior root
• From C1 fibers via hypoglossal nerve

• Inferior root
• From C2 and C3 fibers

• Loop formation
• Inferior root joins superior root → forms the loop

Location

• Lies anterior to carotid sheath

Motor Supply

• Supplies infrahyoid muscles (except thyrohyoid):
• Sternothyroid
• Sternohyoid
• Omohyoid (both bellies)

RLN Identified via Beahr's triangle boundaries

• Boundaries:
• Common carotid artery (lateral).
• Inferior thyroid artery (superior).
• Recurrent laryngeal nerve (RLN) (medial).

• Applied Aspect:
• Identified to prevent RLN injury during surgeries like thyroidectomy.

Triangle of concern

• Berry ligament-RLN-Trachea

Deep Cervical Fascia

Layers

• Investing layer

• Pretracheal layer
• Encloses thyroid gland

• Carotid sheath

• Prevertebral layer

Nerves Enclosed

Cervical → Scale → Scalenus

Investing Layer of Deep Cervical Fascia

Suprasternal Space (Burn's Space):

• Located above the sternum.

• Contains:
• Interclavicular Ligament
• Jugular Venous Arch
• Sternal Head of SCM

• Burn → Veyilath nirthi
• School of head (Head of SCM)
• appoint Interclass Leader (Interclavicular Ligament)
• give him Jug of Water (Jugular vein)

Supraclavicular Space:

• Contents:
• External Jugular Vein
• Supraclavicular nerves
• Medial
• Intermediate
• Lateral

Lateral Supraclavicular Nerve

• Branch of cervical plexus

• Derived from C5 root

Applied Aspect

• C5 → Diaphragm pain referred to shoulder tip
• Splenic rupture
• Peritonitis

• Due to common C5 innervation:
• Lateral supraclavicular nerve (C5)
• Phrenic nerve (C5)

Middle Layer of Deep Cervical Fascia

Muscular Layer

• Covers the infrahyoid muscles

Visceral Layer (Pretracheal Fascia)

• Splits and encloses:



• Thyroid gland
• Recurrent laryngeal nerve (RLN)
• Trachea
• Esophagus

• Mnemonic: Preethi (pretracheal) Teacher (Trachea) Thailand (Thyroid) Visa (Visceral) Easily (Esophagus) Readyayi (RLN)

• Posteriorly → forms ligament of Berry
• Applied
• Most common site of RLN injury during surgery
• Prevents downward extension of swelling

Deep Layer of Deep Cervical Fascia

Prevertebral Fascia

• Encloses all vertebral muscles

• Forms floor of posterior triangle

• Gives rise to axillary sheath

• Spinal part of accessory nerve (XI) lies superficially in posterior triangle
• Between investing layer & prevertebral layer

Carotid Sheath

• Formed by contributions from:
• Investing layer
• Pretracheal layer
• Prevertebral layer

Contents

1. Common Carotid Artery

2. ICA

3. IJV

4. Vagus

• 9,11,12 cranial nerves

Relations

• Anterior: Ansa cervicalis

• Posterior: Sympathetic chain

Muscles & Triangles of Neck