The numb arm and hand.

Trauma and compression along the course of the median, ulnar or radial nerve from the brachial plexus to the fingers may cause pain, weakness, numbness or tingling of the upper extremity. Diabetes, smoking, alcohol consumption, rheumatoid arthritis and hypothyroidism are risk factors for nerve entrapment, although these disorders typically produce bilateral symptoms. Carpal tunnel syndrome, the most common nerve entrapment condition, results from median nerve compression at the wrist. The diagnosis is suggested by decreased pain sensation and numbness in the thumb and index and middle fingers; symptoms are reproduced by wrist hyperflexion and median nerve percussion. Volar splinting and steroid injection often ameliorate symptoms. Decreased sensation of the little finger and the ulnar aspect of the ring finger, along with intrinsic muscle weakness, may be caused by cervical radiculopathy, thoracic outlet syndrome or compression of the ulnar nerve above the elbow (cubital tunnel syndrome) or at the wrist (ulnar tunnel syndrome). Electromyography and radiography may help differentiate these conditions. Radial tunnel syndrome occasionally accompanies inflammation of the common wrist extensors and lateral epicondylitis ("tennis elbow"). A radial nerve block can help exclude concomitant radial tunnel syndrome in patients with symptoms of lateral epicondylitis.