Second Cervical Nerve

Origin

The second cervical nerve is a mixed nerve, formed by the union of its posterior nerve root (sensory nerve fibers) with its anterior nerve root (motor nerve fibers). The roots emerge from the posterolateral and anterolateral sulci of the C2 spinal segment and unite to form the second cervical nerve.

Course

The second cervical nerve exits the vertebral column by traveling through the intervertebral foramen situated between the atlas and the axis (first and second cervical vertebrae, respectively). It travels laterally a short distance and bifurcates into anterior and posterior rami.

Branches

The second cervical nerve divides into posterior (dorsal) and anterior (ventral) rami, both of which receive sensory and motor fibers.

The anterior ramus of the second cervical nerve passes anteriorly and contributes to the formation of the cervical plexus (along with the anterior rami of the first to fourth cervical nerves).

The posterior ramus is largest among all cervical posterior rami. It passes posteriorly to emerge between the lamina of the axis and the obliquus capitis inferior muscle, and divides into larger medial (greater occipital nerve) and smaller lateral branches. The dorsal ramus may also give communicating branches to the posterior ramus of the first and third cervical nerves.

Supplied Structures

The anterior ramus of the second cervical nerve conveys motor fibers to the cervical plexus, thus innervating the infrahyoid muscles (sternohyoid, sternothyroid and inferior belly of omohyoid) via the ansa cervicalis. Other muscles innervated include the anterior prevertebral muscles, including rectus capitis anterior and lateralis and longus colli muscles.

The posterior ramus innervates the obliquus capitis inferior muscle via communications sent from the greater occipital nerve to the suboccipital nerve. Fibers which pass through the smaller lateral branch of the posterior ramus innervate the longissimus capitis, semispinalis capitis, and splenius capitis muscles.

Sensory cutaneous fibers ending of the greater occipital nerve reach the scalp by passing through the gap between sternocleidomastoid and trapezius muscles. It ascends, accompanying the occipital artery, to reach the scalp to provide sensory innervation to the skin as far as the coronal suture and behind the auricle, via its communication with the third occipital and lesser occipital nerves.

The second cervical nerve also serves as a conduit for the sensory neurons innervating the meninges and the proprioceptive nerve endings from the sternocleidomastoid muscle.

List of Clinical Correlates

—Greater occipital neuralgia