Radial Nerve Palsy

Photoclinic

A 16-year-old previously healthy boy presented with 3 days of tingling and weakness in his left hand. He awoke and was unable to move his left wrist and fingers. He also reported tingling and pain in his palm. He denied any trauma, abnormal sleep position, or exposure to unusual substances.

Review of systems was negative for fever, upper respiratory tract infection symptoms, headaches, rashes, and altered mental status. Physical examination was remarkable for left wrist drop with wrist/finger extension and subtle decreased elbow extension. His deep tendon reflexes were normal.

He was admitted to the hospital and underwent magnetic resonance angiography of the brain and cervical spine, the results of which were negative for neural compression and vascular or demyelinating disease. Plain radiographs of his left arm showed no fractures or other abnormalities.

The neurology staff performed a nerve conduction study, which revealed a severe conduction block above the radial groove that was consistent with isolated radial nerve palsy. Median nerve and ulnar responses were normal. Needle electromyogram (EMG) also was normal.

Occupational therapy staff evaluated the patient and recommended he use a cock-up wrist splint during functional activities.

Upon discharge, the boy’s pain and tingling had resolved, but the weakness in his left hand continued. A follow-up visit with neurology was scheduled, but the patient did not keep the appointment, since all symptoms had resolved completely within 4 weeks of discharge.

Radial neuropathy is the fourth most common mononeuropathy. It can result from penetrating wounds, fractures, compression, surgical procedures, or ischemia. It also has been called “Saturday night palsy,” referring to the mechanism by which a person places an arm over a chair or other object, with the pressure causing compression of the radial nerve.

Pathophysiology includes three categories of nerve injury: focal damage to the myelin fibers around the axon, with the axon and tissue sheath remaining intact (neurapraxia); injury to the axon itself (axonotmesis); and complete disruption of the axon (neurotmesis). Neurapraxia has a limited course of days to weeks and can have complete recovery; this most likely is what our patient experienced. The degree of injury depends on the severity and extent of nerve compression.

Radial nerve palsy usually presents with wrist drop with weakness of wrist dorsiflexion. If the lesion is high above the elbow, numbness of the forearm and hand may occur. The workup includes plain films to look for causes of nerve compression, magnetic resonance imaging for soft-tissue and nerve evaluation, and occasionally ultrasonography. Nerve conduction studies and needle EMG can give specific localization of the injury.

The initial management of most nerve injuries is nonsurgical. The main component of conservative treatment is physical therapy and wrist splinting, as in our case. However, when the lesion is a result of external entrapment at the spiral groove, decompression followed by conservative management is indicated. If the injury is the result of a humeral fracture, careful orthopedic reduction should be done in order to avoid further nerve damage. The prognosis usually is good but depends on the site and cause of the lesion.