The cervical plexus is a plexus of the ventral rami of the first four cervical spinal nerves which are located from the C1 to C4 cervical segment in the neck. They are located laterally to the transverse processes between prevertebral muscles from the medial side and vertebral (m.scalenus, m.levator scapulae, m.splenius cervicis) from the lateral side. There is anastomosis with accessory nerve, hypoglossal nerve, and sympathetic trunk. It is located in the neck, deep to sternocleidomastoid. Nerves formed from the cervical plexus innervate the back of the head, as well as some neck muscles. The branches of the cervical plexus emerge from the posterior triangle at the nerve point, a point which lies midway on the posterior border of the sternocleidomastoid.
The cervical plexus has two types of branches: cutaneous and muscular.
Cutaneous branches include:
- Lesser occipital nerve - The lesser occipital nerve or small occipital nerve is a cutaneous spinal nerve arising between the second and third cervical vertebrae, along with the greater occipital nerve. It innervates the scalp in the lateral area of the head posterior to the ear.
- Great auricular nerve - The great auricular nerve originates from the cervical plexus, composed of branches of spinal nerves C2 and C3. It provides sensory innervation for the skin over parotid gland and mastoid process, and both surfaces of the outer ear.
- Transverse cervical nerve - The transverse cervical nerve (superficial cervical or cutaneous cervical) arises from the second and third cervical nerves, turns around the posterior border of the sternocleidomastoideus about its middle, and, passing obliquely forward beneath the external jugular vein to the anterior border of the muscle, it perforates the deep cervical fascia, and divides beneath the platysma into ascending and descending branches, which are distributed to the antero-lateral parts of the neck.
- Supraclavicular nerves - The supraclavicular nerves (descending branches) arise from the third and fourth cervical nerves. They emerge beneath the posterior border of the sternocleidomastoideus, and descend in the posterior triangle of the neck beneath the platysma and deep cervical fascia.
Muscular branches include:
- Ansa cervicalis (loop formed from C1-C3), (geniohyoid (C1 only), thyrohyoid (C1 only), sternothyroid, sternohyoid, omohyoid): The ansa cervicalis is a loop of nerves that are part of the cervical plexus.
- Phrenic (C3-C5 (primarily C4)) - The phrenic nerve is a nerve that originates in the neck and passes down between the lung and heart to reach the diaphragm.
- Segmental branches (C1-C4) - These branches innervate anterior and middle scalenes.