Expansion
Hand of benediction, ape hand and loss of thumb opposition
Mnemonic
Two levels, two signs:
- High lesion, at the elbow: hand of benediction on attempted fist, since the index and middle fingers cannot flex, plus loss of pronation
- Low lesion, at the wrist: ape hand, with thenar wasting and the thumb pulled into the plane of the palm, so opposition is lost
Motor supply in the hand is LOAF: Lateral two lumbricals, Opponens pollicis, Abductor pollicis brevis, Flexor pollicis brevis.
Carpal tunnel syndrome spares sensation over the thenar eminence, because the palmar cutaneous branch arises proximal to the flexor retinaculum and passes over rather than through the tunnel.
Expansion
- Hand of benediction - on trying to make a fist, the index and middle fingers stay extended because of loss of the long flexors (high lesion)
- Ape hand - flat thenar eminence with the thumb pulled back in line with the palm from loss of opposition
- Sensory loss - over the lateral three and a half fingers on the palmar side
- Carpal tunnel syndrome - the commonest low median nerve lesion, causing tingling in the same distribution, worse at night