Causes and Treatment of Radial Nerve Injuries

The radial nerve travels from the back of the neck, down the arm, and to the fingertips. If it's injured, radial nerve pain can occur when your palm is pressed against something and your wrist is bent back.

It's typically a sharp, radiating, or burning pain in the back of the hand, around the thumb, and in the middle and index fingers. Often, the pain is accompanied by the inability to fully straighten your arm or fingers.

Along its path to your fingertips, the radial nerve communicates with muscles and skin to trigger movement and send sensory messages back to the brain. Depending on where the nerve damage occurs, the symptoms can vary both by sensation and the restriction of movement.

Injury at the Axilla

Immediately after leaving the brachial plexus (a network of nerves situated at the root of the neck), the radial nerve travels under the arm close to the armpit (axilla). Improper use of crutches is a common cause of radial nerve compression at this point.

The radial nerve is responsible for controlling the triceps muscles situated at the back of the arm. Because of this, any damage to the nerve at the axilla will cause weakness of the arm, particularly if you're pushing something away.

It may also be impossible to bend your wrist back, resulting in "wrist drop." Finger extensor muscles may also be weakened, making it difficult to fully open your hand.

In addition to weakness, people with a radial nerve injury at the axilla may experience tingling and numbness from the back of the arm to the hand, especially along the side and back of the thumb.

Injury at the Spiral Groove

After leaving the axilla, the radial nerve travels down the arm and wraps around the humerus (the large bone between the shoulder and elbow) in a channel known as the spiral groove.

The nerve can become compressed within this groove and interfere with your ability to bend the wrist back and straighten your fingers.

A radial injury of this sort may occur as a result of a humerus fracture or a condition known as "Saturday night palsy" in which you fall asleep with an arm draped over the back of a chair.

Posterior Interosseous Nerve Injury

Just before entering the elbow, a section of the radial nerve branches off to the posterior interosseous nerve, which is responsible for straightening anything below the elbow.

Unlike other branches of the radial nerve, the posterior interosseous nerve has no sensory receptors and is purely responsible for muscle movement. As a result, injuries are characterized by muscle weakness but no abnormal sensation. The inability to extend your fingers is often a tell-tale sign.

The only exceptions are the muscles of the wrist, which are predominantly controlled by a different set of nerves. If the wrist is affected, it would only show up in the position of the hand.

For example, your hand may be pulled more to one side than the other when the wrist is extended. The brachioradialis and the triceps muscles will both be spared.

Despite the lack of abnormal sensations, an injury to the posterior interosseous nerve can be very painful, especially when the fingers are extended.

Superficial Radial Neuropathy

As the radial nerve passes the elbow, it continues down to the back of the hand, where it serves a purely sensory function.

At that point, the nerve is most susceptible to injury at the wrist, such as when the wrists are bound or handcuffs are worn too tightly.

The pattern of numbness is usually worst from the wrist to the back of the thumb. It may also be accompanied by a "pins and needles" sensation or shooting pains up or down the back of the hand.

Prognosis and Treatment

When a radial nerve injury is diagnosed, treatment is usually conservative and includes:

• Wrist splinting to maintain function
• Pain management with nonsteroidal anti-inflammatory drugs (NSAIDs)
• Physical therapy

In extreme cases, a nerve block may be recommended.

Recovery time can range from a couple of weeks to six months. If your pain and disability don't improve, your doctor may order nerve conduction studies or electromyography (EMG). Based on the findings, surgery may be advised.