Median nerve injury at wrist, is commonly tested by-
Though the lateral three fingers, lateral half of ring finger and corresponding region of palm are supplied by median nerve, test for sensory loss by median nerve injury is done on the autonomous zone (Tip of middle and index fingers).
Flexion of thumb can also be produced by flexor pollicis longus. So for testing median nerve injury, abductor pollicis brevis is tested.
Contraction of abductor pollicis brevis
Contraction flexor pollicis brevis
Loss of sensation on palm
Loss of sensation on ring finger