Cervical plexus

The cervical plexus is a complex network of nerves formed by the anterior (ventral) rami of the cervical spinal nerves C1 to C4. It lies within the muscles that constitute the floor of the posterior triangle of the neck. The ventral rami of these nerves emerge in the groove between the longus capitis (anteriorly) and the scalenus medius muscle (posteriorly). As each ramus emerges anteriorly to the scalenus medius muscle, it divides into ascending and descending branches that interconnect to form a series of loops.

Relationship to surrounding structures

These loops of cervical plexus are situated lateral to the transverse processes of the cervical vertebrae and deep to structures such as the internal jugular vein, superior cervical sympathetic ganglion, and the sternocleidomastoid muscle.

Branches of the Cervical Plexus

The cervical plexus gives rise to superficial (sensory) branches and deep (motor) branches:

1. Superficial branches (sensory)

The superficial branches provide sensory innervation to the skin of the neck, the upper thoracic region, and parts of the scalp. These include the lesser occipital (C2), great auricular (C2, C3), transverse cervical (C2, C3), and supraclavicular (C3, C4) nerves.

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2. Deep branches (motor)

The deep branches of the cervical plexus primarily serve motor functions, supplying various neck muscles. These include the prevertebral muscles of the neck, the sternocleidomastoid and trapezius, the diaphragm, the geniohyoid and thyrohyoid muscles, and the long infrahyoid muscles innervated via the ansa cervicalis.

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3. Autonomic connections

The cervical plexus also has autonomic connections. The gray rami communicantes from the superior cervical ganglion connect the sympathetic trunk to the anterior rami of the cervical spinal nerves, forming an important link between the cervical plexus and the autonomic nervous system.

Clinical Correlations

A thorough understanding of the cervical plexus anatomy is essential for procedures like nerve blocks and surgical interventions in this region. The cervical plexus can be anesthetized at Erb’s Point, located at the midpoint of the posterior border of the sternocleidomastoid muscle. This is utilized for pain management or anesthesia during surgeries in the neck, such as lymph node biopsies or carotid endarterectomy.