The brachial plexus is a network of nerve fibers belonging to the peripheral nerve group that supplies the skin and musculature of the upper limb. It begins at the base of the neck, passes through the armpit, and runs through the entire upper limb.

Injury to the brachial plexus in infants at birth causes paralysis or weakness of the upper limb muscles and loss of sensation, followed by changes in the sympathetic nervous system, soft tissue contractures and limb deformities. Clinical manifestations are weak or absent movements of the paralyzed arm, leg, or hand, flaccid muscles, and decreased or lost sensation in the skin of the arm.