Carpal Tunnel Syndrome (CTS) refers to compression of the median nerve as it crosses the wrist. The median nerve begins, as all nerves do, in the brain. This nerve travels from the brain to the spinal cord, then exits the cord at the neck. It crosses the front of the shoulder and continues down the arm and forearm, eventually crossing the wrist. As the nerve crosses the wrist, it passes through an anatomic tunnel. The Latin word for wrist is “carpal,” hence, the tunnel at the wrist is the “carpal tunnel”. Three sides of this tunnel are formed by the bones of the wrist, but the roof of the tunnel is made of a soft tissue called the transverse carpal ligament, also known as the flexor retinaculum.
After the median nerve passes through the carpal tunnel, it sends branches or nerve endings to both borders of the thumb, index, and middle fingers. It also sends nerve endings to the thumb side of the ring finger. The connection between fingertips and brain allows the fingers to feel. Further, the nerve also controls the group of muscles at the base of the thumb, assisting with thumb motion in rotation.
CTS may be the result of trauma to the wrist (fractures of the wrist or direct blows to the area of the carpal tunnel). Significant exposure to vibration or some repetitive activities seem to be associated with carpal tunnel syndrome, but the relationship between nerve compression at the wrist and workplace activities is now considered controversial. Additionally, certain conditions such as obesity, diabetes, and hypothyroidism seem to be associated with CTS.
People with CTS often describe a feeling of numbness or tingling to the thumb, index, middle, and radial side of the ring finger. Some patients describe this feeling as their hand being so numb that it hurts. Others describe aching discomfort in the muscles at the base of the thumb, while some feel as if their hand is swollen. Still others feel a combination of these symptoms. Additionally, people with CTS feel as if their whole arm falls asleep, and may occasionally feel aching discomfort traveling up the arm. These symptoms seem to be most prevalent at night often waking people from sleep. Further, certain activities make the symptoms worse, such as driving a car, holding a book or a phone, or trying to use the hands to brush hair or put on makeup.
The diagnosis of CTS is made by a description of the symptoms, but also by the use of certain maneuvers that usually recreate the symptoms. Nerve conduction studies (NCS) such as electrodiagnostic and electromyography (EMG) help to confirm the diagnosis. The nerve studies serve not only to pinpoint the area of nerve compression, but also give the treating physician a sense of the severity of nerve injury. This information is used to direct the treatment and predict the likelihood of complete recovery.
There is no conclusive evidence that carpal tunnel syndrome can be prevented.