Median nerve. Compression of the median nerve at the base of the palm in canal bound by bone and the traverse carpal ligament. Swelling in the canal increases pressure on the median nerve causing numbness and tingling in the thumb, index, long and half the ring fingers. Can get weakness of thenar muscles and loss of coordination as well.
Pinched nerve. Carpal tunnel syndrome is a pinched median nerve which causes numbness, tingling, pain (especially at night) and weakness. The median nerve travels thru a tunnel surrounded by bone on 3 sides and covered by the rigid transverse carpal ligament. In cts, the tunnel is filled with 9 swollen flexor tendons, which leaves little room for the median nerve. That causes the nerve to be pinched.