The long thoracic nerve (external respiratory nerve of Bell; posterior thoracic nerve) supplies the Serratus anterior. This nerve characteristically arises by three roots from the fifth, sixth, and seventh cervical nerves

Cervical nerves

The cervical nerves are the spinal nerves from the cervical vertebrae.Although there are seven cervical vertebrae , there are eight cervical nerves . All nerves except C8 emerge above their corresponding vertebrae, while the C8 nerve emerges below the C7 vertebra...

 (C5-C7) but the root from C7 may be absent. The roots from C5 and C6 pierce the Scalenus medius

Scalenus medius

The Scalenus medius, the largest and longest of the three scalene muscles, arises from the posterior tubercles of the transverse processes of the lower six cervical vertebræ. It descendes along the side of the vertebral column to insert by a broad attachment into the upper surface of the first...

, while the C7 root passes in front of the muscle.

The nerve descends behind the brachial plexus

Brachial plexus

The brachial plexus is a network of nerve fibers, running from the spine, formed by the ventral rami of the lower four cervical and first thoracic nerve roots...

 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

Muscle

Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...

, supplying filaments to each of its digitations (finger-like projections).

Damage

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. Surgically the long thoracic nerve can also be damaged during surgery for breast cancer

Breast cancer

Breast cancer is cancer originating from breast tissue, most commonly from the inner lining of milk ducts or the lobules that supply the ducts with milk. Cancers originating from ducts are known as ductal carcinomas; those originating from lobules are known as lobular carcinomas...

, specifically radical mastectomies

Mastectomy

Mastectomy is the medical term for the surgical removal of one or both breasts, partially or completely. Mastectomy is usually done to treat breast cancer; in some cases, women and some men believed to be at high risk of breast cancer have the operation prophylactically, that is, to prevent cancer...

 that involve removal of axillary lymph nodes

Axillary lymph nodes

The Axillary lymph nodes are of large size, vary from twenty to thirty in number, and may be arranged in the following groups:* brachial lymph nodes * pectoral 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

Parsonage Turner Syndrome

Parsonage-Turner syndrome is also known as acute brachial neuropathy and acute brachial radiculitis. Other names used are Parsonage-Aldren-Turner syndrome, neuralgic amyotrophy, brachial neuritis, brachial plexus neuropathy, or brachial plexitis.The idiopathic syndrome refers to a rare set of...

, 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 winged scapula

Winged scapula

A winged scapula is a condition in which the shoulder blade, or shoulder bone, protrudes from a person’s back in an abnormal position. It is a rare condition with the potential to lead to limited functional activity in the upper extremity with which it is adjacent. It can affect a person’s ability...

, 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 later.

External links

- "The major subdivisions and terminal nerves of the brachial plexus

Brachial plexus

The brachial plexus is a network of nerve fibers, running from the spine, formed by the ventral rami of the lower four cervical and first thoracic nerve roots...

."