Quick Facts
Origin: Formed by the union of anterior and posterior roots emerging from the C3 spinal cord segment.
Course: Travels laterally for a short distance to the bifurcation of anterior and posterior rami.
Branches: Anterior and posterior rami.
Supply: Motor innervation to the infrahyoid and anterior prevertebral muscles, middle scalene, semispinalis capitis, longissimus capitis, and splenius capitis muscles. Sensory innervation to the scalp below superior nuchal line, anterolateral neck, and meninges.
Origin
The third 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 C3 spinal segment and unite to form the third cervical nerve.
Course
The third cervical nerve exits the vertebral column by traveling through the intervertebral foramen situated between the axis (second cervical vertebra) and the third cervical vertebra. It travels laterally a short distance and bifurcates into anterior and posterior rami.
Branches
The third cervical nerve divides into posterior (dorsal) and anterior (ventral) rami, both of which receive sensory and motor fibers.
The anterior ramus of the third 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 winds posteriorly around the C3 articular pillar and divides into medial and lateral branches. The lateral branch passes dorsally across the semispinalis capitis, innervates various muscles and sends a communicating branch to the posterior rami of the second and fourth cervical nerves. The medial branch, or third occipital nerve, curves posteriorly and medially around the C3 articular pillar and gives off muscular and articular branches, before ending in multifidus muscle. It gives rise to a superficial posterior cutaneous branch, which curves around the lateral and dorsal surfaces of the C2—C3 facet joint, which it innervates. Next, it continues to run deep to semispinalis and then pierces it to become cutaneous.
Supplied Structures
The anterior ramus of the third 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 the longus capitis and longus colli, and lateral prevertebral muscles, including the middle scalene muscle.
Sensory afferent neurons from the great auricular, supraclavicular, and transverse cervical nerves also transmit general sensory information from the skin of the anterolateral neck via the anterior ramus.
The posterior ramus innervates the semispinalis capitis, longissimus capitis, and splenius capitis muscles.
Some sensory afferent neurons, which provide innervation to the skin below the superior nuchal line, transmit general sensory information regarding pain, touch, pressure, vibration, etc. via the medial branch of dorsal ramus.
The third cervical nerve also serves as a conduit for the sensory neurons innervating the meninges.
