Causes of Carpal Tunnel Syndrome
In many cases, the cause of Carpal Tunnel Syndrome is difficult to determine. It generally tends to appear more often in people with a congenital predisposition - a smaller wrist and carpal tunnel - as well as people with certain risk factor, such as obesity, alcohol abuse, smoking, or mental stress. Symptoms usually appear due to an increase in pressure on the median nerve and flexor tendons within the carpal tunnel. This pressure can be cause by a number of factors including a wrist injury or trauma, hypothyroidism, rheumatoid arthritis, diabetes, work requiring repetitive motion, fluid retention during menopause or pregnancy, repetitious work with power tools, or a tumor. Once problems begin in the carpal tunnel and wrist it is difficult to heal due to the lack of blood flow and oxygen to the wrist joint. Whatever the cause may be, the condition is usually signaled by gradually increasing symptoms over time.
To understand how the pressure is put on the median nerve, it is important to understand the anatomy of the wrist. The transverse carpal ligament runs like a bridge across the inside of the wrist at the base of the palm. The carpal tunnel lies beneath this ligament and is surrounded by small carpal bones that allow the wrist to move in different directions. The median nerve lies between the transverse ligament and the flexor tendons within the carpal tunnel. When CTS symptoms occur, pressure on the nerve is generally caused by tightening due to swelling and inflammation within the carpal tunnel. As space in the tunnel decreases there is no longer room for the fluid movement of tendons through the sheath, pinching the nerve against the transverse carpal ligament, causing tingling, numbness, more inflammation and eventually pain.
Repetitive and Vibration Motions at Work
It is argued that a common cause of CTS is a Repetitive Strain Injury (RSI). Computer work is one of the most popular causes of carpal tunnel syndrome in regards to RSI. The use of a keyboard and mouse over time, without proper posture or equipment, can aggravate CTS symptoms. Every time you type, you are flexing and extending the wrist and fingers requiring the tendons that run inside the carpal tunnel to slide through their protective sheath.
Working with tools that vibrate, like a chain saw, jack-hammer, and other power tools, causes small repetitive movements of the tendons within the sheath. The tendons become overused with the repetitive motion and inflammation can set in. When these motions are performed in colder temperature, the risk of CTS increases even more. Some of the higher risk jobs include electrician, meat packers, road worker, seamstress or tailor, cleaner and assembly line worker. In fact, CTS is 3 times more common among assemblers than computer entry employees.
The sheath acts as a protective tube to separate the tendon from the surrounding tissues and prevent any adhesions from forming to the tendon itself. If the sheath becomes irritated due to the amount of repetitive movement and rubbing of the tendon through it, tendonitis develops. When tendonitis develops, the carpal tunnel becomes inflamed and causes compression on the median nerve.
Conditions Affecting the Nerves and Wrists
Swelling within the wrist can also cause the carpal tunnel to be squeezed and pressure to be applied to the median nerve. Some conditions that can cause swelling are rheumatoid arthritis or thyroid deficiency (pituitary gland hormone imbalance). When swelling occurs, the area within the wrist becomes tighter and the tendons have difficulty moving smoothing through the sheath. When the wrist is used and the tendon have difficulties moving freely, inflammation occurs and CTS symptoms begin. Conditions affecting the nerves within the body, such as diabetes, can also make them more susceptible to compression.
Single Traumatic Event
It is less common, but single acute traumatic incidents can cause carpal tunnel strain or carpal tunnel syndrome as well. Fractures of the wrist bones (the carpal bones) as well as fractures of the distal radius near the wrist can cause CTS. Acute injuries that do not break bones but stress the wrist excessively (even if for only a very short period of time, such as in a rear end motor vehicle accident while grasping the steering wheel) can cause this problem.
Tenosynovitis and Tendonitis Can Lead to CTS
Tendonitis means inflammation of a tendon.
(It is sometimes spelled as 'tendinitis')
Tenosynovitis means inflammation of the sheath that surrounds a tendon (the sheath is called the synovium). Tenosynovitis can be caused by calcium deposits, repeated strain or trauma, high levels of blood cholesterol, rheumatoid arthritis, gout, or gonorrhea.
These two conditions often occur together.
