Causes and Treatment of Radial Nerve Injuries

Radial nerve pain can be described as the type that occurs when your palm is pressed against something and your wrist bent back. The sharp, radiating, or burning pain is typically felt in the back of the hand, around the thumb, and in the middle and index fingers. Oftentimes, the pain is accompanied by the inability to fully straighten your arm or fingers.

The radial nerve itself is one that travels from the back of the neck, down the arm, and to the fingertips. Along the way, it 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.

Immediately after leaving the brachial plexus (the network of nerves situated at the root of the neck), the radial nerve will travel 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 tricep 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 pushing something away. It may also be impossible to bend the wrist back, resulting in "wrist drop." Finger extensors may also be weakened, making it difficult to fully open the 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.

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 often become compressed within this groove and interfere with a person's ability to bend the wrist back and straighten the 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 a person falls asleep with an arm draped over the back of a chair.

While the injury will cause the weakening of the brachioradialis muscle of the forearm, the tricep muscle will be unaffected. Moreover, the weakness will be more noticeable when the muscle is extended rather than when it is flexed.

Just before entering the elbow, a section of the radial nerve will branch 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, an injury would be characterized by muscle weakness rather than any abnormal sensation. The inability to extend one's 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 be seen in the position of the hand. In such case, the hand may be pulled more to one side than the other when the wrist is extended. The brachioradialis and the tricep 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.

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

If a radial nerve injury is diagnosed, treatment would typically involve the restriction of movement so that the nerve has time to heal. This may include the splinting of the wrist accompanied by the use of nonsteroidal anti-inflammatory drugs (NSAIDs) to help control pain. In extreme cases, a nerve block may be recommended.

Recovery time can range from a couple of weeks to six months. For those whose pain and disability do not improve, further investigations may be needed in the form of nerve conduction studies or electromyography (EMG). Based on the findings, surgery may be advised.