77 Radial nerve palsy
Salient features
History
• An intoxicated person sleeping with the head resting in the upper arm, causing compression of the nerve over the middle third of the humerus; this is known as Saturday night palsy
• Trauma to the nerve while it courses through the axilla: crutch palsy, shoulder dislocation, fractures of humerus or radius
Examination
• There is weakness of extension of the wrist and elbow (wrist flexion is normal).
• The patient is unable to straighten the fingers.
• However, if the wrist is passively extended, the patient is able to straighten the fingers at the interphalangeal joints (caused by the action of interossei and lumbricals) but is unable to extend the metacarpophalangeal joint.
• There appears to be a weakness in abduction and adduction of the fingers, but this is not present when the hand is kept flat on a table and the fingers are extended.
• Test the brachoradialis, looking for weakened elbow flexion. When the patient attempts to flex the elbow against resistance, the brachioradialis no longer springs up.
• Check sensation over the first dorsal interosseous (Fig. 77.1).
