Axillary nerve dysfunction

Axillary nerve dysfunction

Definition:

Axillary nerve dysfunction is a condition involving impaired movement or sensation of the shoulder because of damage to the axillary nerve.

Alternative Names:

Neuropathy - axillary nerve

Causes, incidence, and risk factors:

Axillary nerve dysfunction is a form of peripheral neuropathy. It occurs when there is damage to the axillary nerve, which supplies the deltoid muscles of the shoulder. It is not a specific, separate disease, but is a manifestation of many conditions that can cause damage to the axillary nerve.

Dysfunction of a single nerve group, such as the axillary nerve, is classed as mononeuropathy. Mononeuropathy implies a local cause of the nerve damage, although systemic disorders may occasionally cause isolated nerve damage (such as occurs with mononeuritis multiplex).

The usual causes are direct trauma, prolonged external pressure on the nerve, and pressure on the nerve from nearby body structures.

Conditions associated with axillary nerve dysfunction include fracture of the humerus (upper arm bone), pressure from casts or splints, and improper use of crutches. Other causes include systemic disorders that cause neuritis (inflammation of nerves).

In some cases, no detectable cause can be identified. Mechanical factors may be complicated by ischemia (a lack of oxygen from decreased blood flow) in the area.

Symptoms:

Numbness over part of the outer shoulder
Shoulder weakness
- Difficulty lifting objects with the affected arm
- Difficulty lifting arm above the head

Signs and tests:

A neuromuscular examination of the arm and shoulder indicates axillary nerve dysfunction. There may be weakness of the shoulder, with difficulty moving the arm.

The deltoid muscle of the shoulder may show signs of muscle atrophy. A detailed history may be needed to determine the possible cause of the neuropathy.

Tests that reveal axillary nerve dysfunction may include:

An EMG (a recording of electrical activity in muscles)
A nerve biopsy (may reveal systemic causes for the dysfunction)

Other tests are guided by the suspected cause of the nerve dysfunction, as suggested by the history, symptoms presented, and pattern of symptom development. They may include various blood tests, x-rays, scans, or other tests and procedures.

Treatment:

Treatment is aimed at identifying the cause, treating it, and maximizing mobility and independence. In some cases, no treatment is required and recovery is spontaneous.

If there is no history of trauma to the area, conservative treatment is indicated by the sudden onset of symptoms, minimal sensation changes and no difficulty in movement, and no test evidence of nerve axon degeneration.

Corticosteroids injected into the area may reduce swelling and pressure on the axillary nerve in some cases. Systemic corticosteroids may be recommended for cases that are secondary to inflammatory lesions (such as brachial amyotrophy and brachial neuritis).

Surgical intervention is indicated if the disorder is chronic or symptoms are worsening, if there is difficulty with movement, or if there is evidence on testing that degeneration of the nerve axon is present.

Surgical exploration may be necessary to discover that the nerve dysfunction is caused by entrapment, in which case surgical decompression of the area may be of benefit.

Surgical removal of tumors (or other conditions) that press on the nerve may benefit some cases.

Over-the-counter analgesics (such as acetaminophen - oral) or prescription analgesics may be needed to control pain (neuralgia). Other medications including gabapentin, phenytoin, carbamazepine or tricyclic antidepressants such as amitriptyline, may be used to reduce the stabbing pains that some people experience Whenever possible, their use should be avoided or minimized to reduce the risk of side effects.

Physical therapy exercises may be appropriate for some people to maintain muscle strength. Vocational counseling, occupational therapy, job retraining, or similar intervention may be recommended to help maximize independence.

Expectations (prognosis):

If the cause of the axillary nerve dysfunction can be identified and successfully treated, there is a possibility of full recovery. The extent of disability varies. The worst problem most often is shoulder weakness.

Complications:

Partial or complete arm paralysis
Partial or complete loss of sensation in the arm (uncommon)
Recurrent or unnoticed injury to the arm
Deformity of the arm, shoulder contracture or fibrosis (frozen shoulder)

Calling your health care provider:

Call for an appointment with your health care provider if symptoms of axillary nerve dysfunction are present. Early diagnosis and treatment increase the chance of controlling symptoms.

Prevention:

Preventative measures vary, depending on the cause.
Avoid prolonged pressure on the underarm area. Examine casts, splints, and other appliances for proper fit. Crutch training should include instructions not to place pressure on the underarm.

Review Date: 7/19/2001
Reviewed By: Galit Kleiner-Fisman, M.D., FRCP(C), Department of Neurology, University of Toronto, Toronto, Ontario, Canada. Review provided by VeriMed Healthcare Network.

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