2 – Anatomy of the deep cervical plexus

The deep cervical plexus is sandwiched between the upper part of the medial scalene muscle and the longus capitis muscle and it consists of:

– Ansa cervicalis – a cervical plexus loop with a superior and an inferior root.
The superior root is a branch of the C1 ventral ramus. It briefly joins the hypoglossal nerve.
The inferior root is derived from branches of the C2 ventral rami.

The superior root descends on the carotid sheath. It innervates the superior belly of the omohyoid muscle and the upper parts of the sternothyroid and sternohyoid muscles before it unites with the inferior root. The inferior root of the ansa cervicalis is derived from branches of the C2 and C3 ventral rami. It innervates the inferior belly of the omohyoid muscle and the inferior parts of the sternothyroid and sternohyoid muscles.

– Phrenic nerve from C3-C5 innervates the diaphragm and the pericardium
– Branches from C1-C4 innervate the anterior and middle scalene muscles