A patient tries to make a fist but the index and middle finger remain partially extended. The nerve most probably involved is

Answer: (a) Median nerve.MEDIAN NERVE INJURY* When the median nerve is severed in the elbow region, flexion of the proximal interphalangeal joints of the lst-3rd digits is lost and flexion of the 4th and 5th digits is weakened.* Flexion of the distal interphalangeal joints of the 2nd and 3rd digits is also lost.* Flexion of the distal interphalangeal joints of the 4th and 5th digits is not affected because the medial part of the FDP is supplied by the ulnar nerve.* The ability to flex the metacarpophalangeal joints of the 2nd and 3rd digits is affected because the digital branches of the median nerve supply the 1st and 2nd lumbricals.* Thus, when the person attempts to make a fist, the 2nd and 3rd fingers remain partially extended (hand of Benediction).* Thenar muscle function (function of the muscles at the base of the thumb) is also lost, as in carpal tunnel syndrome.* When the anterior interosseous nerve is injured, the thenar muscles are unaffected, but paresis (partial paralysis) of the flexor digitorum profundus and flexor pollicis longus occurs.* When the person attempts to make the "okay" sign, opposing the tip of the thumb and index finger in a circle, a "pinch" posture of the hand results instead owing to the absence of flexion of the interphalangeal joint of the thumb and distal interphalangeal joint of the index finger (anterior interosseous syndrome)