Definition of Axillary nerve dysfunction:

Axillary nerve dysfunction is nerve damage that leads to a loss of movement or sensation in the shoulder.

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 and the skin around it. A problem with just one nerve, such as the axillary nerve, is called mononeuropathy.

The usual causes are:

• Direct trauma
• Long-term pressure on the nerve
• Pressure on the nerve from nearby body structures
• Shoulder injury

Entrapment creates pressure on the nerve where it passes through a narrow structure.

The damage may destroy the myelin sheath that covers the nerve, or part of the nerve cell (the axon). Damage of either type reduces or prevents the movement of impulses through the nerve.

Conditions that can lead to axillary nerve dysfunction include:

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

In some cases, no cause can be found.

Symptoms:

• Numbness over part of the outer shoulder
• Shoulder weakness, especially when lifting the arm up and away from the body

Signs and tests:

Your health care provider will examine your neck, arm, and shoulder. Weakness of the shoulder may cause difficulty moving your arm.

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

Tests that may be used to evaluate axillary nerve dysfunction include:

• EMG and nerve conduction tests -- will be normal right after the injury; should be performed several weeks after the injury or symptoms start
• MRI or x-rays of the shoulder

Treatment:

Depending on the cause of the nerve disorder, some people do not need treatment. They will get better on their own. However, the rate of recovery can be different for everyone. It can take many months to recover.

Anti-inflammatory medications may be given if you have:

• Sudden symptoms
• Small changes in sensation or movement
• No history of injury to the area
• 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.

Other medicines include:

• Over-the-counter pain medicines may be helpful for mild pain (neuralgia).
• Other medications (phenytoin, carbamazepine, gabapentin, pregabalin, duloxetine, or tricyclic antidepressants such as nortriptyline) may reduce the stabbing pains that some people experience.
• Opiate pain relievers, such as morphine or fentanyl, may be needed to control severe pain.

Whenever possible, avoid or reduce medication use to lessen the risk of side effects.

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.

Expectations (prognosis):

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

Complications:

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

Calling your health care provider:

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.

Prevention:

Preventive measures vary, depending on the cause. Avoid putting pressure on the underarm area for a long period of time. Make sure casts, splints, and other appliances fit properly. When you use crutches, learn how to avoid putting pressure on the underarm.