Long thoracic nerve

The long thoracic nerve (external respiratory nerve of Bell; posterior thoracic nerve) supplies the serratus anterior muscle. This nerve characteristically arises from the anterior rami of three spinal nerve roots: the fifth, sixth, and seventh cervical nerves (C5-C7) although the root from C7 may be absent. The roots from C5 and C6 pierce through the scalenus medius, while the C7 root passes in front of the muscle. The nerve descends through the cervicoaxillary canal behind (posterior to) the brachial plexus and the axillary artery and vein, 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). Due to its long, relatively superficial course, it is susceptible to injury either through direct trauma or stretch. Injury has been reported in almost all sports, typically occurring from a blow to the ribs underneath an outstretched arm. The long thoracic nerve can also be damaged during surgery for breast cancer, specifically radical mastectomies that involve removal of axillary lymph nodes. 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.