Damage to which nerve may lead to wrist drop?

Damage to which nerve may lead to wrist drop?

• A. Radial
• B. Axillary
• C. Median
• D. Ulnar

Answer: (A)

Wrist drop occurs when the nerve that powers the wrist extensors is damaged. The radial nerve supplies the extensor muscles of the forearm and wrist (like the extensor digitorum, extensor carpi radialis longus/brevis, and extensor carpi ulnaris). If this nerve is injured, those extensors can no longer pull the wrist into extension, so the hand and wrist sag into flexion at rest—producing wrist drop. Other nerves wouldn’t produce this pattern because their muscles control different actions: the axillary nerve mainly affects deltoid and shoulder abduction; the median nerve injures forearm flexors and some hand muscles, leading to problems with thumb opposition and finger flexion; the ulnar nerve affects intrinsic hand muscles and finger spreading. Thus, only radial nerve damage disrupts wrist extension enough to cause wrist drop.

Wrist drop occurs when the nerve that powers the wrist extensors is damaged. The radial nerve supplies the extensor muscles of the forearm and wrist (like the extensor digitorum, extensor carpi radialis longus/brevis, and extensor carpi ulnaris). If this nerve is injured, those extensors can no longer pull the wrist into extension, so the hand and wrist sag into flexion at rest—producing wrist drop.

Other nerves wouldn’t produce this pattern because their muscles control different actions: the axillary nerve mainly affects deltoid and shoulder abduction; the median nerve injures forearm flexors and some hand muscles, leading to problems with thumb opposition and finger flexion; the ulnar nerve affects intrinsic hand muscles and finger spreading. Thus, only radial nerve damage disrupts wrist extension enough to cause wrist drop.