Wartenberg's sign indicates injury to which nerve?

• A. Median nerve
• B. Ulnar nerve
• C. Radial nerve
• D. Pudendal nerve

Answer: (B)

Wartenberg's sign reveals loss of adduction of the little finger due to paralysis of the palmar interossei, muscles that bring the digits toward the middle finger. These interossei are innervated by the ulnar nerve, so when the nerve is injured, the little finger cannot be drawn toward the ring finger and remains abducted. This specific deficit is a classic indicator of ulnar nerve palsy in the hand. The other nerves listed don’t control these intrinsic hand adductors—they affect different muscles or areas (median nerve for other intrinsic hand muscles and forearm flexors, radial nerve for extension, pudendal nerve is not involved in upper limb function).