Carpal Tunnel Syndrome - Causes

Injuries

Bone dislocations and fractures can narrow the carpal tunnel, thereby exerting pressure on the median nerve.

Obesity and Lack of Fitness

Being overweight consistently turns up as a risk factor for CTS and may play a direct causal role on CTS. Greater body mass appears to reduce nerve flow speed into the hand. Obesity is also related to poor physical fitness, which may also increase risk. A 2005 analysis indicated that weight is strongly linked to the onset of CTS in patients under the age of 63 years, but may be a less important factor as they get older.

Hormonal Changes

Hormonal fluctuations in women play a role in CTS. Such fluctuations may cause fluid retention and other changes in the body that cause swelling. Fluid retention is one reason that CTS may develop during pregnancy.

Genetic Factors

CTS is strongly associated with a family history of the disorder. Many of these cases can be attributed to physical characteristics or medical conditions associated with CTS that also run in families. However, in one study, 17% of family clusters of CTS were not associated with any such medical conditions, suggesting the genetic factors may be important in some people. Carpal tunnel that develops in young people is most likely to have a genetic component.

For example, a 2000 study suggested that some patients with CTS may have a genetic defect that produces higher levels of a certain collagen subtype. (Collagen is the protein that is used to build all connective tissue, muscle, bones, and ligament.) The collagen found in CTS patients tends to produce stiffness.

Other genetic defects that may contribute to this disorder include abnormalities in certain genes that regulate myelin, a fatty substance that serves as insulation for nerve fibers.