Carpal Tunnel Syndrome

What Causes Carpal Tunnel Syndrome?

We don’t always know what causes carpal tunnel syndrome. In fact, in most cases no obvious cause can be found.

However, any condition that lessens the amount of space in the carpal tunnel or narrows the tunnel can potentially result in compression of the median nerve within the tunnel. Such conditions usually result in swelling around the tunnel or alteration of the normal anatomy of the wrist due to injury or growth of a benign lesion.

These include:

  • Various injuries, including previous fractures of the wrist (the change in anatomy may narrow the tunnel)
  • Medications that may lead to fluid retention, including oral contraceptives (birth control pills)
  • Hormonal changes and conditions that lead to fluid retention, such as pregnancy (CTS that occurs during pregnancy usually disappears within four to six weeks following delivery)
  • Medical disorders that lead to fluid retention or are associated with inflammation, such as rheumatoid arthritis, diabetes, hypothyroidism, Lyme disease, and others.
  • Benign growths within the wrist for example a ganglion (cyst)
  • Medical disorders that involve constricted blood vessels, such as Raynaud’s disease

The following can increase the chance of developing carpal tunnel syndrome:

  • Cigarette smoking, which constricts blood vessels
  • Obesity, which can increase pressure on the nerves in the wrist

Carpal Tunnel Syndrome and Repetitive Strain Injuries (RSI):

During the 1970s it became popular to attribute many painful conditions of the upper limb joints and tendons to what became known as “Repetitive Strain Injuries” (RSI), and later as “Cumulative Trauma Disorders” (CTD). These types of injuries were said to result from prolonged overuse of the upper extremities by performing  repetitive motions of the shoulders, elbows, hand, or fingers, usually in the workplace.

Back then this was not initially accepted by all physicians, and until late 1990’s many physicians questioned the validity of the diagnosis of Repetitive Strain Injury.

Now it is universally accepted that such injuries, including Carpal Tunnel Syndrome, may result from repetitive movements of the wrist in the workplace.

  • Repetitive movements and prolonged overuse inflames the tendons’ protective layer, called the synovial sheath, causing the sheath to swell.
  • The swollen tendons may place pressure on the median nerve in the carpal tunnel.
  • Thus, nerve impulses are disrupted and the normal functioning of the nerve is impaired.

Repetitive strain injuries:

  • Have been the fastest growing category of occupational illness
  • Are the leading cause of job-related illness
  • Accounted for 64% and more of all reported workplace illnesses





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