Evidence For Traumatic Cause of Carpal Tunnel Syndrome

The cause of carpal tunnel syndrome

New Mayo Clinic research suggests that a shearing injury of the tissue that lines the tendons within the carpal tunnel may cause carpal tunnel syndrome, a debilitating condition of the wrist and hand. If validated by further research, Mayo's study comparing electron microscope images of carpal tunnel syndrome tissue with those from normal tissue could lead to earlier diagnosis and possibly better treatments for preventing or reversing carpal tunnel syndrome.

The study appears in the November issue of Plastic and Reconstructive Surgery.

In the study, the Mayo researchers present data which suggest that the carpal tunnel syndrome disease process begins with a shearing injury. As the injury heals, the resulting scar tissue impedes the sliding motion of the tendon, compresses the median nerve, cuts off the nerve's blood supply and eventually leads to the pressure buildup characteristic of carpal tunnel syndrome, a condition that affects an estimated five percent of adults. The end result of this process is the familiar carpal tunnel syndrome symptoms of hand pain, numbness and tingling associated with carpal tunnel syndrome.

The Mayo research offers an explanation for the cause of carpal tunnel syndrome. Although carpal tunnel syndrome is a well-recognized condition, in most cases the specific cause has been unknown. What is well known is that a pressure buildup in the carpal tunnel affects the circulation nourishing the nerves, which can lead to pain, numbness and tingling. The question Mayo researchers explored was: What leads to the pressure buildup? Their results indicating shearing injury as a possible cause present promising new ways to approach treating carpal tunnel syndrome.

The Mayo work is significant because it:

• provides a detailed analysis of carpal tunnel syndrome tissue abnormalities

• shows that the tissue closest to the tendon is the most disturbed, thus providing circumstantial evidence to support the presence of a shearing injury in carpal tunnel patients that is not present in individuals without the condition

• points to new directions for designing better ways to diagnose and possibly treat carpal tunnel syndrome by addressing a first cause of carpal tunnel syndrome, the shearing injury to the tendon lining

"The idea is that if we can identify the sequence of events that lead to carpal tunnel syndrome, we can design more effective interventions to prevent or reverse it," according to Peter Amadio, M.D., the Mayo Clinic orthopedic surgeon who led the NIH-funded research team.

While rest, exercise and some medications can treat carpal tunnel syndrome, severe carpal tunnel syndrome is commonly treated surgically to release the pressure buildup.

The study did not specifically probe the cause of the shearing injuries, but Dr. Amadio says the team is researching the role of trauma or stress to the tissue lining from repeated finger movements. "Such shearing injuries could be the result of marked or repetitive differential motion of adjacent digits, and may support the hypothesis of a traumatic cause for carpal tunnel syndrome," he says.