Other Reasons for Carpal Tunnel Syndrome

Things that take up space in the tunnel can affect the median nerve. 

or instance if you have a disease that makes the covering on the tendons thicker, then the nerve has less room.  This can happen if rheumatoid arthritis or hypothyroidism goes untreated.  
 
You might get carpal tunnel syndrome if space in the tunnel is taken up with blood from a fracture or wound.   The same thing can happen if pus from an infection takes up space in the tunnel. 
 
Women born with narrow tunnels may feel more numbness when they are pregnant.  This is probably due to some fluid or swelling in the carpal tunnel associated with being pregnant.  The numbness will often improve--at least temporarily--after the baby is delivered.
 
You often hear or read about people getting carpal tunnel syndrome from what they do with their hands.  The evidence for that is weak and inconsistent.  What’s certain is that blaming hand use doesn’t help people with carpal tunnel syndrome be healthier.