9.19 Radial Neuropathy (Saturday Night Palsy)

agk’s Library of Common Simple Emergencies

Presentation

The patient has injured his upper arm, usually by sleeping with his arm over the back of a chair, and now presents holding the affected hand and wrist with his good hand, complaining of decreased or absent sensation on the radial and dorsal side of his hand and wrist, and of inability to extend his wrist, thumb and finger joints. With the hand supinated (palm up) and the extensors aided by gravity, hand function may appear normal, but when the hand is pronated (palm down) the wrist and hand will drop.

What to do:

• Look for associated injuries. This sort of nerve injury may be associated with cervical spine fracture, injury to the brachial plexus in the axilla, or fracture of the humerus.
• Document in detail all motor and sensory impairment. Draw a diagram of the area of decreased sensation, and grade muscle strength of various groups (flexors, extensors, etc.) on a scale of 1-5.
• If there is complete paralysis or complete anesthesia, arrange for additional neurological evaluation and treatment right away. Incomplete lesions may be satisfactorily referred for followup evaluation and physical therapy.
• Construct a splint, extending from proximal forearm to just beyond the metacarpophalyngeal joint (leaving the thumb free) which holds the wrist in 90 degree extension. This and a sling will help protect the hand, also preventing edema and distortion of tendons, ligaments, and joint capsules which can result in loss of hand function after strength returns.
• Explain to the patient the nature of his nerve injury, the slow, rate of regeneration, the importance of splinting and physical therapy for preservation of eventual function, and arrange for followup.

What not to do:

• Do not be misled by the patient’s ability to extend the inter phalangeal joints of the fingers, which may be accomplished by the ulnar-innervated interosseus muscles.

Discussion

This neuropathy is produced by compression of the radial nerve as it spirals around the humerus. Most commonly it occurs when a person falls asleep, intoxicated, held up by his arm thrown over the back of a chair. Less severe forms may befall the swain who keeps his arm on his date’s chair back for an entire double feature, ignoring the growing pain and paresis. If the injury to the radial nerve is at the elbow or just below, there may be sparing of the wrist radial extensors as well as the radial nerve autonomous sensation. The deficient groups will be the wrist ulnar extensors as well as the metacarpophalyngeal extensors. A high radial palsy in the axilla (e.g., from leaning on crutches) will involve all of the radial nerve innervations, including the triceps.

Illustration

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