The nerve descends behind the brachial plexus and the axillary vessels, resting on the outer surface of the Serratus anterior. It extends along the side of the thorax to the lower border of that muscle, supplying filaments to each of its digitations (finger-like projections).
Injuries to the nerve can result from carrying heavy bags over the shoulder for a prolonged time. There are also reports of isolated damage to this nerve as a variant of Parsonage Turner Syndrome, an autoimmune disease.
Symptoms are often minimal – if symptomatic, a posterior shoulder or scapular burning type of pain may be reported.
A lesion of the nerve paralyses the serratus anterior to produce scapula winging, which is most prominent when the arm is lifted forward or when the patient pushes the outstretched arm against a wall. However, even winging may not be evident until the trapezius stretches enough to reveal an injury several weeks prior.