The brachial plexus is a neural plexus (a grouping and branching of nerves) located deep in the neck, shoulder, and maxilla region that is responsible for the proper innervation and control of the muscles of the shoulder, upper chest, and arms (upper limbs). Because of the complexities of branching nerve roots, trunks, and cords of the brachial plexus, injuries to the brachial plexus region often cause loss or impairments of function at distant muscle groups.

The nerves forming the brachial plexus come from spinal nerves, specifically the last four cervical and first thoracic spinal nerve. The cervical nerves are designated C5, C6, C7, and C8. Although there are only seven cervical vertebrae, there are eight cervical nerves. The thoracic spinal nerve is designated as T1. Spinal nerves result from the unification of dorsal and ventral spinal roots in the intervertebral foramen. The spinal nerves then divide...