Corpus: Cervical plexus

The cervical plexus is a network of nerves formed by the anterior branches of the spinal nerves from segments C1 to C4, with contributions from C5. Its branches pass into the deep cervical region between the anterior and middle scalenus muscles.

The cervical plexus provides motor branches to the anterior neck muscles, the lower hyoid muscles, and the diaphragm. Its sensory branches supply the skin of the ear, the neck, the area above the clavicle, and the shoulder.

3.1. Sensitive branches

The sensitive branches of the cervical plexus are located in the superficial cervical fascia, where they emerge in a star-shaped pattern from the posterior edge of the sternocleidomastoid muscle at a point called the punctum nervosum (Erb's point). These sensory branches include:

• Ascending branches (C2 and C3):
  • Lesser occipital nerve: Supplies sensation to the lower lateral part of the occipital region.
  • Greater auricular nerve: Supplies the auricle (external ear) and the surrounding skin.
  • Transverse cervical nerve: Innervates the anterior surface of the neck and the skin below the chin. Together with the cervical branch of the facial nerve, it forms the superficial cervical nerve.
• Descending branches (C3 and C4):
  • Supraclavicular nerves: A group of three nerves that supply the skin of the lower neck, the shoulder, and the area extending about 4-6 cm below the clavicle. These include:
    • Medial supraclavicular nerve
    • Intermediate supraclavicular nerve
    • Lateral supraclavicular nerve

3.2. Motor branches

The motor branches of the cervical plexus innervate the deep neck muscles, the scalenus muscles, the levator scapulae, the diaphragm, and the lower hyoid muscles. Some fibers from C3 and C4 also join the accessory nerve (cranial nerve XI) to innervate the trapezius and sternocleidomastoid muscles. The motor branches include:

• Medial branches:
  • Prevertebral branches (C1-C4): These supply the deep neck muscles, including the longus colli, longus capitis, rectus capitis lateralis, and rectus capitis anterior muscles.
  • Infrahyoid branches (C1-C3): The superior root (from C1 and C2) joins the inferior root (from C2 and C3) to form the ansa cervicalis, which innervates the entire lower hyoid musculature (omohyoid, sternohyoid, sternothyroid, and thyrohyoid muscles). Additionally, some fibers from C1 and C2 travel with the hypoglossal nerve to supply the geniohyoid muscle.
  • Diaphragmatic branches (C3 and C4): These form the phrenic nerve, which also receives fibers from C5 of the brachial plexus. The phrenic nerve is the motor nerve of the diaphragm and also carries sensory fibers for the pleura, pericardium, and peritoneum.
• Lateral branches:
  • To the sternocleidomastoid muscle (C2, C3)
  • To the trapezius muscle (C2-C4)
  • To the scalenus muscles (C3, C4)
  • To the levator scapulae muscle (C3, C4)

• "C3, C4, C5 keep the diaphragm alive."

see also: brachial plexus, lumbar plexus, sacral plexus