Carpal tunnel syndrome is a nerve entrapment disorder that results from compression of the median nerve which winds its way through the wrist through a narrow passageway called the carpal tunnel.
This compression typically causes pain, numbness, and tingling in the thumb, index finger, middle finger, and the thumb side of the ring finger, which are the areas of skin innervated by the median nerve.
Now taking a cross section of the wrist, we’ll see a bony arch known as a carpal arch on the dorsal side of the hand which forms the floor of the carpal tunnel, and a sheath of connective tissue called the flexor retinaculum or transverse carpal ligament, which is on the palmar side of the hand forms the roof of the carpal tunnel.
Also there are nine flexor tendons, which go to the fingers and thumb, as well as one nerve—the median nerve—which travels down the forearm and go through the carpal tunnel.
The skin of the hand served by the median nerve includes the thumb, the index finger, and middle finger, as well as half of the ring finger that’s on the thumb side.
The other side of the ring finger and pinky are served by the ulnar nerve, and the back of the hand’s served by the radial nerve, only the median nerve goes through the carpal tunnel.
Carpal tunnel syndrome is caused by compression of the median nerve, and that typically happens as a result of inflammation of the nearby tendons and tissues, which creates local edema or swelling which increases the amount of fluid in a very tight space, and essentially puts pressure on the median nerve.