Posterior triangle of the neck

The posterior triangle (or lateral cervical region) is a region of the neck.

Boundaries

It has the following boundaries:

Apex: Union of the sternocleidomastoid and the trapezius muscles at the superior nuchal line of the occipital bone

Anterior: Posterior border of the sternocleidomastoideus

Posterior: Anterior border of the trapezius

Base: Middle one third of the clavicle

Divisions

The posterior triangle is crossed, about 2.5 cm above the clavicle, by the inferior belly of the Omohyoideus, which divides the space into two triangles:

• an upper or occipital triangle
• a lower or subclavian triangle (or supraclavicular triangle)

Contents

A) Nerves and Plexuses:

• Spinal accessory nerve (Cranial Nerve XI)
• Branches of cervical plexus
• Roots and trunks of brachial plexus
• Phrenic nerve (C3,4,5)

B) Vessels:

• Subclavian artery (Third part)
• Transverse cervical artery
• Suprascapular artery
• Terminal part of external jugular vein

C) Lymph Nodes:

• Occipital
• Supraclavicular

D) Muscles:

• Inferior belly of omohyoid muscle
• Anterior Scalene
• Middle Scalene
• Posterior Scalene
• Levator Scapulae Muscle
• Splenius Muscle

Clinical significance

The Accessory Nerve (CN XI) is particularly vulnerable to damage at lymph node biopsy, where damage results in an inability to shrug the shoulders or raise the arm above the head (eg, for brushing hair).

The external jugular vein's superficial location also makes it vulnerable to......
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