CorpusHuman Anatomy
NervousPlexus

Cervical plexus

Plexus cervicalis

Also known as: C1–C4 plexus, ansa cervicalis, Erb point

A network formed by the ventral rami of C1–C4, lying deep to sternocleidomastoid. It supplies the skin of the neck, ear and shoulder, the infrahyoid strap muscles (via the ansa cervicalis), and, most importantly, the diaphragm (via the phrenic nerve, C3–C5).

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Overview

RootsC1–C4 ventral rami
Cutaneous emergenceErb's point (mid-posterior border of SCM)
Most important branchPhrenic nerve (C3–C5)

The cervical plexus is formed by a series of loops between the ventral rami of C1–C4. It lies on the levator scapulae and middle scalene, deep to the internal jugular vein and sternocleidomastoid, and is covered by the prevertebral fascia. Its branches fall into two groups. The superficial (cutaneous) branches fan out from the nerve point of the neck (Erb's point), at about the midpoint of the posterior border of sternocleidomastoid. The deep (mainly motor) branches supply the prevertebral and strap muscles and the diaphragm.

The ansa cervicalis is a loop lying on or in the carotid sheath:
• its superior root (C1) travels briefly with the hypoglossal nerve;
• its inferior root (C2–C3) joins it.

The ansa supplies sternohyoid, sternothyroid and omohyoid. C1 fibres that continue with CN XII supply thyrohyoid and geniohyoid. The plexus also sends proprioceptive fibres to sternocleidomastoid and trapezius (with CN XI). Its most vital branch is the phrenic nerve.

Location

Neck, deep to sternocleidomastoid, opposite C1–C4, on the scalenus medius and levator scapulae.

Parts & subdivisions

  1. Ansa cervicalis
    A loop (C1–C3) on the carotid sheath supplying sternohyoid, sternothyroid and omohyoid. Surgeons preserve it during thyroid surgery, or divide the strap muscles high up, close to their nerve entry. Its descending branch can be used to reinnervate a paralysed recurrent laryngeal nerve.
  2. Great auricular nerve
    C2–C3. It ascends across sternocleidomastoid toward the parotid gland and is the largest ascending branch. It may be injured in parotidectomy (numb earlobe) and is a common donor for nerve grafts. It is the reason the angle of the mandible is not in the trigeminal territory.
  3. Supraclavicular nerves
    C3–C4. They supply the skin over the clavicle and the shoulder tip. Pain from structures supplied by the phrenic nerve (C3–C5), such as the diaphragm, is therefore referred to the shoulder tip.

Anatomy

Innervation

- Skin: the anterolateral neck, the lower auricle and angle of the jaw (not trigeminal), the occipital scalp behind the ear, and the skin over the clavicle and shoulder tip.
• Muscles: the infrahyoid strap muscles, the prevertebral muscles and the diaphragm.

Nerve roots

Ventral rami of C1–C4. The phrenic nerve also takes C5.

Branches

Cutaneous (all emerging at Erb's point):
• Lesser occipital (C2): scalp behind the ear.
• Great auricular (C2–C3): skin over the parotid, the angle of the mandible and the auricle.
• Transverse cervical (C2–C3): anterior neck.
• Supraclavicular nerves (C3–C4), medial, intermediate and lateral: skin over the clavicle, upper chest and shoulder.

Motor:
• Ansa cervicalis (C1–C3): the infrahyoid muscles.
• C1 via CN XII: thyrohyoid and geniohyoid.
• Phrenic nerve (C3–C5).
• Segmental branches to longus colli and capitis, rectus capitis anterior and lateralis, the scalenes and levator scapulae.
• Contributions to SCM and trapezius.

Function

  • Cutaneous sensation of the neck, posterior scalp, auricle and shoulder
  • Motor supply to the infrahyoid muscles (stabilising the hyoid for swallowing and speech)
  • Motor and sensory supply of the diaphragm (phrenic nerve)
  • Postural control of the head (prevertebral muscles)

Clinical significance

Superficial cervical plexus block

Local anaesthetic injected at the midpoint of the posterior border of sternocleidomastoid anaesthetises the cutaneous branches. It is used for carotid endarterectomy, clavicle fixation and superficial neck surgery. The deep cervical plexus block carries a risk of phrenic nerve paralysis.

Mnemonics

Cutaneous branches

"Little Girls Take Sweets": Lesser occipital, Great auricular, Transverse cervical, Supraclavicular.

Compiled from standard anatomy and physiology references — see the Nervous System sources. For education only; not medical advice.