With median nerve palsy, wasting of the thenar muscles is common. Other features are dependent on the site of the lesion.
A lesion at the wrist produce weakness of abduction and opposition of the thumb and may create difficulty in fine manipulation, e.g. picking up a pin. This can be tested by asking the patient to lie his hand flat and then abduct his thumb upwards - a movement requiring abductor pollicis brevis.
There is sensory loss in the palmar aspect of the thumb and index finger, and usually, also of the middle and lateral half of the ring fingers. Loss of sensation to the nail beds of the radial three and a half fingers is also typical.
A lesion at the level of the forearm produces additional weakness of flexion of the distal and middle phalanges.
At the elbow and above, there is also weakness of pronation of the forearm and deviation of the wrist to the ulnar surface on wrist flexion.
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