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 can compress the median nerve in the tunnel. These include:

 
• Various injuries, including previous fractures of the wrist  
• 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 involve constricted blood vessels, such as Raynaud’s disease  
• Medical disorders that lead to fluid retention or are associated with inflammation, such as rheumatoid arthritis, diabetes, hypothyroidism, Lyme disease, and others.

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

Some researchers believe that overuse of the wrist may be a cause of carpal tunnel syndrome. But this is not accepted by all physicians. Today, repetitive strain injury is becoming less recognized as the entity causing carpal tunnel symptoms. Indeed, many physicians now question the validity of this diagnosis.

Those who believe in RSI as a cause of carpal tunnel syndrome assume that:

 
• Unnatural bending 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% of all reported workplace illnesses in 1996, up from 33% ten years earlier