Sixth Cervical Nerve (Left)

Origin

The sixth 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 C6 spinal segment and unite to form the sixth cervical nerve.

Course

The sixth cervical nerve exits the vertebral column by traveling through the intervertebral foramen situated between the fifth and sixth cervical vertebrae. It travels laterally a short distance and bifurcates into anterior and posterior rami.

Branches

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

The anterior ramus of the sixth cervical nerve passes anteriorly and contributes to the formation of the brachial plexus (along with the anterior rami of the fifth to eighth cervical and first thoracic nerves).

The posterior ramus winds posteriorly around the C6 articular pillar and divides into medial and lateral branches.

Supplied Structures

The anterior ramus of the sixth cervical nerve conveys motor fibers to the superior trunk of the brachial plexus. Fibers that enter the lateral cord of the brachial plexus help innervate muscles of the anterior compartment of the arm (biceps brachii, coracobrachialis, brachialis), pectoralis major, pronator teres, and flexor carpi radialis. Fibers that enter the posterior cord provide motor innervation to the subscapularis, teres major, latissimus dorsi, deltoid, teres minor, triceps, brachioradialis, anconeus, extensor carpi radialis longus, and supinator. Some fibers also contribute to the innervation of the subclavius and supra- and infraspinatus muscles.

Some sensory fibers from the skin around the lateral upper limb also travel via the anterior ramus of the sixth cervical nerve.

The lateral branch of the posterior ramus of the sixth cervical nerve provides somatic motor innervation to the longissimus colli, splenius colli, and iliocostalis colli muscles. Those which pass through the medial branch provide motor innervation to multifidus, semispinalis colli, semispinalis capitis, and trapezius, before becoming cutaneous.

The sensory afferent neurons, which provide innervation to the skin above the trapezius transmit general sensory information regarding pain, touch, pressure, vibration, etc. via the medial branch of the dorsal ramus.