nerve damage produces inability to flex the index finger and, to a lesser
degree, the middle fingers.
Flexion of the distal phalanx of the thumb and opposition of the thumb
are weak. Forearm pronation is also weak. Efforts to make a fist produces
a typical hand posture that has the appearance of a priest giving benediction.
This posture is due to the inability to flex the index and middle fingers
(benediction hand). Long-standing intrauterine median nerve lesions
may produce an abnormal appearance called “simian hand” or “ape hand”
due to atrophy of the thumb muscles innervated by the median nerve and
the unopposed action of the extensor pollicis longus (innervated by
the radial nerve) and the adductor pollicis (innervated by the ulnar