The hand of benediction refers to the pattern of muscle paralysis that occurs with a proximal lesion of the Median nerve when the patient attempts to make a fist.
Pathophysiology
The proximal lesion results in loss of the motor branches to the long finger flexors in the forearm:
M. flexor digitorum superficialis: Flexion at the PIP joints (proximal interphalangeal joints) of all fingers is absent.
M. flexor digitorum profundus: Flexion at the DIP joints (distal interphalangeal joints) of the index finger (Dig. II) and middle finger (Dig. III) is absent.
M. flexor pollicis longus: Flexion of the distal phalanx of the thumb is absent.
The ulnar portion of the M. flexor digitorum profundus for Dig. IV and V is innervated by the Ulnar nerve and remains intact.