Wartenberg’s sign indicates impairment of which nerve?

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

Answer: (C)

Wartenberg’s sign reflects loss of the intrinsic hand muscles innervated by the ulnar nerve, especially the interossei that adduct and abduct the fingers. When the ulnar nerve is impaired, these interossei can’t adduct the little finger toward the ring finger, so the little finger remains in an abducted position due to unopposed action of the abductor digiti minimi. This abnormal posture is characteristic of ulnar nerve impairment at the hand. In contrast, signs from the radial, median, or axillary nerves produce different patterns (radial: wrist/finger extension weakness; median: thenar/precision pinch issues; axillary: deltoid weakness).