Axillary nerve dysfunction is a loss of movement or sensation of the shoulder because of nerve damage.

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. A problem with just one nerve group, such as the axillary nerve, is called mononeuropathy.

The usual causes include direct trauma, prolonged pressure on the nerve, and compression of the nerve from nearby body structures. Entrapment involves pressure on the nerve where it passes through a narrow structure.

The damage may include destruction of the myelin sheath of the nerve or destruction of part of the nerve cell (the axon). Damage to the axon slows or prevents conduction of impulses through the nerve.

Direct injury to the shoulder and pressure on the nerve can lead to axillary nerve dysfunction.

Conditions associated with axillary nerve dysfunction include:

• Fracture of the upper arm bone
• Pressure from casts or splints
• Improper use of crutches
• Shoulder dislocation
• Body-wide disorders that cause nerve inflammation

In some cases, no cause can be identified.

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

Your health care provider will examine the arm and shoulder. There may be weakness of the shoulder with difficulty moving the arm.

The deltoid muscle of the shoulder may show signs of muscle atrophy.

Tests that reveal axillary nerve dysfunction may include:

• EMG -- will be normal right after the injury; it should be performed several weeks after the injury or symptoms start
• Nerve biopsy
• MRI

Some people do not need treatment, and they get better on their own but the rate of recovery is variable and can take many months.

Anti-inflammatory medications may be given if you have sudden symptoms, little sensation or movement changes, no history of injury to the area, and no signs of nerve damage. These medicines reduce swelling and pressure on the nerve. They may be injected directly into the area or taken by mouth.

You may need over-the-counter or prescription pain medicines to control pain. If you have stabbing pains, your doctor may prescribe other medications, such as carbamazepine, gabapentin, or certain tricyclic antidepressants such as amitriptyline or nortriptyline.

If your symptoms continue or get worse, you may need surgery. Surgery may be done to see if a trapped nerve is causing your symptoms. In this case, surgery to release the nerve may help you feel better.

Physical therapy may help you maintain muscle strength. Job changes, muscle retraining, or other forms of therapy may be recommended.

It may be possible to make a full recovery if the cause of the axillary nerve dysfunction can be identified and successfully treated.

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

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

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.

Pryse-Phillips W, Murray T. Peripheral neuropathies. In: Noble J. Textbook of Primary Care Medicine. 3rd ed. St. Louis, Mo: Mosby; 2001:chap 167.