Hand Deformities in Nerve Palsy

Mnemonic

Three nerves, three hands:

• Median - the hand of benediction on trying to make a fist, since the index and middle fingers cannot flex, and an ape hand at rest from thenar wasting with the thumb adducted
• Ulnar - the claw hand, worse in the ring and little fingers
• Radial - wrist drop, with the extensors paralysed

The ulnar paradox: a more distal ulnar lesion produces a worse claw, because a high lesion also paralyses flexor digitorum profundus to the ring and little fingers, so there is nothing left to flex them into the claw.

Expansion

• Radial nerve - wrist drop (loss of wrist and finger extension)
• Ulnar nerve - claw hand, worst in the ring and little fingers
• Median nerve - hand of benediction on making a fist, and an ape hand with thenar wasting at the wrist

Remember: the radial nerve extends, so its loss drops the wrist; the ulnar nerve works the intrinsics, so its loss claws the hand.