Carpal tunnel syndrome (CTS) is a disorder characterised by tingling and pain in the hand and fingers due to damage to the median nerve. The pain may radiate up the arm as far as the elbow; although, not usually into the elbow itself. The median nerve is one of three major nerves of the upper arm that contains motor, sensory, and autonomic fibres. Injury of the median nerve results in a disruption of nervous function in the first three and one-half digits and the thenar eminence (body of muscle on the palm of the hand just beneath the thumb.) Compression (squeezing) of the median nerve in the carpal tunnel is the most common nerve entrapment syndrome. CTS is usually idiopathic (of unknown cause – 47% of cases), but it may also result from a variety of processes that decrease the space of the carpal tunnel.
CTS is characterized by pinching of the median nerve within the carpal tunnel. This pinching is caused by the swelling of protective sheaths (tenosynovium) surrounding the tendons within the carpal tunnel. When the muscles become irritated from the exposures listed in the next section they begin to swell in size. The protective sheaths surrounding the tendons secrete a lubricating fluid called synovium. By secreting synovium, the amount of space within the carpal tunnel is further reduced which causes the muscle tendons to rub upon each other and become even more irritated. As a result, more synovium is secreted to reduce the irritation. What results is the disorder known as CTS. Since the tendons are now irritated and inflamed, and the protective sheaths have secreted synovium, the amount of space within the carpal tunnel is limited. This results in impingement (pinching) of the median nerve which also passes through the carpal tunnel. It is this impingement that results in the tingling and pain that one experiences.
Double Crush Syndrome
Refers to compression of the median nerve at more than one location. This is typically seen in the wrist and in the neck/shoulder area. If you’re suffering from CTS, please be sure your doctor has thoroughly examined you to determine if your CTS is due to a Double Crush Syndrome. A hand specialist may overlook a Double Crush originating in the neck. A proper examination for CTS would include the entire arm and neck in order to trace the full length of the nerve, especially if they’ve been recommended for carpal tunnel surgery.
What is the Carpal Tunnel?
The carpal tunnel is a narrow, rigid passageway of bones at the base of the hand (wrist), while the top is formed by the Transverse Carpal Ligament. Tendons pass between these two structures allowing movement of the fingers. The median nerve (a nerve that runs down the arm and forearm) passes through the carpal tunnel and into the hand and gives sensation to the thumb, index finger, long finger, and half of the ring finger. The tendons are important because they allow movement of the fingers, thumb, and hand (i.e. grasping). These tendons are covered by a substance called tenosynovium, which is a slippery covering that allows the tendons to glide next to each other as they are worked.