Which nerve palsy is classically associated with a drop wrist?

Which nerve palsy is classically associated with a drop wrist?

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

Answer: (D)

The key idea is that wrist extension is lost when the nerve that powers the wrist extensors is damaged. The radial nerve supplies the extensor muscles of the forearm (including the extensors of the wrist and fingers). If this nerve is injured, those muscles can’t pull the wrist into extension, so the hand rests with the wrist flexed—the classic “wrist drop.” This presentation is commonly seen with radial nerve palsy from a midshaft humeral fracture or compression around the arm. The other nerves produce different patterns: median nerve palsy affects thumb opposition and some forearm flexors, leading to a different hand posture; ulnar nerve palsy causes clawing of the ulnar fingers and interossei weakness; axillary nerve palsy impairs shoulder abduction due to deltoid loss. But when the hallmark is the inability to extend the wrist, radial nerve palsy is the best fit.

The key idea is that wrist extension is lost when the nerve that powers the wrist extensors is damaged. The radial nerve supplies the extensor muscles of the forearm (including the extensors of the wrist and fingers). If this nerve is injured, those muscles can’t pull the wrist into extension, so the hand rests with the wrist flexed—the classic “wrist drop.” This presentation is commonly seen with radial nerve palsy from a midshaft humeral fracture or compression around the arm.

The other nerves produce different patterns: median nerve palsy affects thumb opposition and some forearm flexors, leading to a different hand posture; ulnar nerve palsy causes clawing of the ulnar fingers and interossei weakness; axillary nerve palsy impairs shoulder abduction due to deltoid loss. But when the hallmark is the inability to extend the wrist, radial nerve palsy is the best fit.