The cervical plexus is a network of nerve fibers that supplies innervation to some of the structures in the neck and trunk. It is located in the posterior triangle of the neck, halfway up the sternocleidomastoid muscle, and within the prevertebral layer of cervical fascia. The cervical plexus is formed from the anterior primary rami of C1–C4, deep to the sternocleidomastoid muscle and in front of the scalenus medius and levator scapulae muscles.