Paralysis refers to a temporary or permanent loss or impairment of motor or sensory function in a part. The radial nerve, predominantly a motor nerve, arises from the middle trunk of the brachial plexus (see Diagnostic Code: 8511 Middle radicular group-Paralysis of). This nerve innervates the main extensors of the forearm, wrist, and fingers.

The middle third of the arm is the most common site of radial nerve injury. Injury to the radial nerve may be caused by damage to the nerve fibers, cell body, or myelin sheath. Causes of the damage may include: lacerations; blunt trauma; gunshot wounds; fractures of the humerus; dislocation of the radius; and compression of the nerve by crutches, watchbands, handcuffs, entrapment, prolonged elbow extension, tumors, and inflammatory conditions.

Signs and symptoms of the condition may include: triceps paralysis; loss of triceps reflex; impaired elbow extension; elbow pain; weakness or paralysis of extension of the wrist, thumb and fingers; weakness of hand adduction; wrist drop; loss of grip; and loss of supination in forearm extension. Atrophy may develop with complete lesions of the nerve. There may be slight sensory loss localized to small areas of the hand, thumb, index and middle fingers as well as pain in the affected areas.

Diagnostic measures may include: a complete history; physical and neurological examinations; motor, sensory and reflex tests; blood studies; spinal tap; evoked responses; electromyography (EMG); x-ray; computed tomography (CT) scan; and magnetic resonance imaging (MRI).

Treatments may include management of the underlying disorder. In some cases, there may be no specific treatment. Measures of treatment may include: wrist splints; passive range of motion (ROM) exercises; anti-inflammatory or pain medications; transcutaneous electrical nerve stimulation (TENS); antibiotics; and vitamin therapy. In some cases, surgery may be needed when recovery is poor or weakness progresses.

Regeneration of the nerve may depend on the degree and site of injury. The closer the injury is to the central nervous system (CNS), regeneration of a severely damaged nerve is less likely to occur. Mild compression injuries, as well as injury from fractures, may resolve spontaneously in a matter of weeks. Recovery from weakness may take several months. Total triceps paralysis is rare as supination may be possible with biceps action, and forearm extension may be attainable by gravity. Painful paresthesias, or dysesthesias of the wrist may develop. There may be a need for long-term pain management. There also may be alteration of employment and daily activities requiring counseling intervention.