What is Carpal Tunnel Syndrome?

The carpal tunnel is an anatomical structure in the wrist. This tunnel has a roof, a floor, and two walls. The roof is made of the transverse carpal ligament. The floor and walls are composed of wrist bones called carpal bones (see Figure 1). The carpal tunnel is the passageway through which the median nerve and finger flexor tendons pass from the forearm into the hand.

An average wrist has adequate space for the median nerve and flexor tendons in the carpal tunnel. In individuals with carpal tunnel syndrome, the space for the nerve is too tight, leading to increased pressure on the nerve. This has the potential to disrupt the blood supply of the median nerve, leading to nerve dysfunction.

The median nerve emerges from the spinal cord in the neck and runs down the arm, to the forearm, and through the carpal tunnel into the hand. In the forearm, the median nerve controls muscles that provide wrist and finger flexion. In the hand, it provides sensation to the palm side of the thumb, index, middle, and half of the ring finger in addition to supplying muscles that are responsible for thumb movement (see Figure 1, 2). 

In simple terms, carpal tunnel syndrome is the median nerve compression within the carpal tunnel. It is the most common nerve compression syndrome (compressive neuropathy) in the upper extremity, affecting 1 in 20 people.

Carpal tunnel syndrome is a complex of signs and symptoms caused by compression of the median nerve at the wrist. Increased pressure within the carpal tunnel and decreased function of the median nerve at the level of the wrist causes numbness and/or tingling of the thumb, index, middle, and half of the ring finger. Advanced carpal tunnel syndrome may cause hand and finger pain, clumsiness, and less commonly weakness.

Carpal tunnel syndrome is responsible for a substantial financial burden on society from lost productivity, wages, and treatment costs. Some carpal tunnel syndrome cases are work-related and treated under worker’s compensation coverage.