Radial nerve dysfunction is a form of peripheral neuropathy. It occurs when there is damage to the radial nerve, which travels down the arm and supplies movement to the triceps muscle at the back of the upper arm. It also provides extension to the wrist and helps in movement and sensation of the wrist and hand.

Dysfunction of a single nerve group (such as the radial 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 that which occurs with mononeuritis multiplex).

The usual causes are direct trauma, prolonged pressure on the nerve, or compression of the nerve caused by swelling or injury of nearby body structures. Entrapment involves pressure on the nerve where it passes through a narrow structure.

The radial nerve may be injured at the axilla (underarm) by direct pressure, such as "crutch palsy," caused by improper use of crutches, or pressure caused by hanging the arm over the back of a chair.

A more common cause of radial nerve dysfunction is trauma that occurs in the upper arm, such as a fracture of the humerus (upper arm bone) or pressure to the upper arm from arm positions during sleep or coma.

"Saturday-night palsy" is a term for an injury that occurs to the radial nerve during deep sleep, such as that which may occur when a person is intoxicated. Prolonged or repeated constriction of the wrist (caused by wearing a tight watch strap, for example) can also cause an injury to terminal portions of the radial nerve.

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

Symptoms can affect the following:

• The hand or forearm (dorsal surface)
• The "thumb side" (radial surface) of the dorsal hand
• The fingers nearest the thumb (2nd and 3rd)

The following symptoms may occur:

• Numbness, decreased sensation, tingling, or burning sensation
• Pain
• Abnormal sensations
• Difficulty extending the arm at the elbow
• Difficulty extending the wrist

A neuromuscular examination of the arm, hand, and wrist can identify radial nerve dysfunction. There may be weakness of the wrist and finger extension muscles (with decreased ability to extend the arm at the elbow), a minor decreased ability to rotate the arm outward (supination), and difficulty lifting the wrist or fingers (extensor muscle weakness).

Wrist drop or finger drop may be present, or there may be atrophy (muscle loss) of some of the muscles of the forearm. A detailed patient history may be needed to determine the possible cause of the neuropathy. Rarely, radial nerve dysfunction may be difficult to differentiate from a stroke in the brain.

Tests that reveal nerve dysfunction may include:

• EMG (a recording of electrical activity in muscles)
• Nerve conduction tests
• Nerve biopsy
• Head MRI (to rule out stroke)

The treatment is aimed at maximizing the ability to use the hand and arm. The cause should be identified and treated as appropriate. In most cases, no treatment is required and recovery is spontaneous.

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

Surgical removal of lesions that press on the nerve may be of benefit.

CONTROL OF SYMPTOMS:
Over-the-counter analgesics or prescription pain medications may be needed to control pain (neuralgia). Various other medications, including phenytoin, carbamazepine, or tricyclic antidepressants such as amitriptyline, may reduce stabbing pains. Steroids (prednisone) may be used to try to minimize swelling.

Whenever possible, use of medications should be avoided or minimized to reduce the risk of medication side effects.

Physical therapy exercises may be appropriate for some people to maintain muscle strength. Orthopedic assistance may maximize the ability to use the hand in severe cases. This may include the use of braces, splints, or other appliances.

Vocational counseling, occupational therapy, occupational changes, job retraining, or similar interventions may be recommended as appropriate.

• Partial or complete loss of wrist or hand movement
• Partial or complete loss of sensation in the hand
• Recurrent or unnoticed injury to the hand
• Mild to severe deformity of the hand