Ape hand deformity is associated with palsy of which nerve?

Ape hand deformity is associated with palsy of which nerve?

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

Answer: (B)

Ape hand deformity reveals loss of thumb opposition due to paralysis of the thenar muscles, which are innervated by the recurrent branch of the median nerve. When these muscles (abductor pollicis brevis, opponens pollicis, and flexor pollicis brevis) stop functioning, the thumb can no longer be opposed to the fingertips, and the thenar eminence atrophies, giving the thumb a flattened, adducted appearance along the side of the hand. If the radial nerve were affected, you’d expect wrist drop from inability to extend the wrist and fingers, not a specific loss of thumb opposition. If the musculocutaneous nerve were damaged, forearm flexion and sensation would be impacted, again not the thumb’s opposition. If the ulnar nerve were involved, there would be problems with finger abduction/adduction and adduction of the thumb rather than opposition.

Ape hand deformity reveals loss of thumb opposition due to paralysis of the thenar muscles, which are innervated by the recurrent branch of the median nerve. When these muscles (abductor pollicis brevis, opponens pollicis, and flexor pollicis brevis) stop functioning, the thumb can no longer be opposed to the fingertips, and the thenar eminence atrophies, giving the thumb a flattened, adducted appearance along the side of the hand.

If the radial nerve were affected, you’d expect wrist drop from inability to extend the wrist and fingers, not a specific loss of thumb opposition. If the musculocutaneous nerve were damaged, forearm flexion and sensation would be impacted, again not the thumb’s opposition. If the ulnar nerve were involved, there would be problems with finger abduction/adduction and adduction of the thumb rather than opposition.