The cervical plexus is a plexus of the ventral rami of the first four cervical spinal nerves which are located from 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 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 (4 branches):
Lesser occipital nerve - innervates lateral part of occipital region (C2 ONLY)
Great auricular nerve - innervates skin near concha auricle (outer ear) and external acoustic meatus (ear canal) (C2&C3)
Transverse cervical nerve - innervates anterior region of neck (C2&C3)
Supraclavicular nerves - innervate region of supraspinatus, shoulder, and upper thoracic region (C3,C4)
-Muscular
Ansa cervicalis (loop formed from C1-C3), etc. (geniohyoid (C1 only), thyrohyoid (C1 only), sternothyroid, sternohyoid, omohyoid)
Phrenic (C3-C5 (primarily C4))-innervates diaphragm and the pericardium
Segmental branches (C1-C4)- innervates anterior and middle scalenes