Nerves - Cervical Plexus

Question 1

Where is it located?

Answer 1

It is located within the posterior triangle of the neck, halfway up the sternocleidomastoid, and within the paravertebral fascia.

The plexus is formed by C1-C4 spinal nerves.

Question 2

Muscular branches

Answer 2

Phrenic nerve - C3-C5 - innervates the diaphagm

Nerve to geniohyoid (C1) and Nerve to thyrohyoid (C1) travels with the hypoglossal nerve to reach their respective muscles.

Ansa cervicalis - a loop of nerves, formed by nerve roots C1-C3.

It gives of four muscular branches:

1) Superior belly of omohyoid
2) Inferior belly of omohyoid
3) Sternohyoid
4) Sternothyroid

These muscles (infrahyoids) depress the hyoid - an important function for swallowing and speech.

Question 3

Other muscular branches

Answer 3

C1-C2 - rectus capitis anterior and lateralis

C1-C3 - longus capitis

C2-C3 - prevertebral muscles and sternocleidomastoid

C3-C4 - levator scapulae, trapezius, scalenus medius

The middle and anterior scalenes also receive innervation from the cervical plexus.

Question 4

Sensory branches

Answer 4

Cutaneous branches - skin of the neck, upper thorax, scalp and ear. These nerves then enter the skin at the middle posterior border of the sternocleidomastoid. This is area is known as the nerve point of the neck (Erb’s point), and is utilised when performing a cervical plexus nerve block.

1) Greater auricular nerve - C2 - C3 roots - innervates external ear and skin over the parotid gland - largest ascending branch of the plexus.
2) Transverse cervical nerve - C2-C3 roots - curves around the posterior aspect of the sternocleidomastoid - innervates anterior neck - it pierces the deep cervical fascia and then branches off superiorly and inferiorly to supply the anterolateral skin of the neck and upper sternum.
3) Lesser occipital nerve - C2 - innervates the posterosuperior aspect of the scalp - nerve curves around the accesory nerve and passes superiorly to the posterior border of the sternocleidomastoid.
4) Supraclavicular nerves - C3-C4 - they arise from the posterior border of the sternocleidomastoid - innervates the skin overlying the supraclavicular fossa and the upper thoracic region and sternoclavicular joint.

Question 5

Clinical relevance - cervical plexus block

Answer 5

Used to provide regional anaesthesia, usually for surgery in the neck region - such as carotid enarterectomy, thyroidectomy, and cervical lymph node excision.

Local anaesthetic is administered at the midpoint of the posterior border of the sternocleidomastoid (Erb’s point).