Clue to Carpal Tunnel Syndrome Found

Nov. 16, 2006 -- A microscopic look at carpal tunnel syndrome may have uncovered the cause of the painful condition.

The carpal tunnel is a narrow passage through the bones and ligaments of the wrist. It protects a main nerve leading to the hand and the tendons that bend the fingers.

In carpal tunnel syndrome, there is pressure on the nerve. That causes worsening pain, weakness, and/or numbness in the hand and wrist, sometimes shooting up the arm.

Although workers who perform repetitive hand motions frequently get carpal tunnel syndrome, there has been little evidence to prove the link. That evidence may now be here.

Mayo Clinic researchers Anke M. Ettema, MD, Peter C. Amadio, MD, and colleagues used powerful microscopes to look inside the carpal tunnels of 11 patients with carpal tunnel syndrome. They also looked at the carpal tunnels of 14 normal cadavers and two cadavers of people with a history of carpal tunnel syndrome.

The study found several parallel layers of tissues connected to the tendons in the carpal tunnel. As the tendon slides through the carpal tunnel, the connections pull these tissues along with it. It's a bit like extending an arm covered with several layers of sleeves.

In all of the carpal tunnel syndrome patients, the researchers found, the connective tissues appeared to be damaged, causing bulky fibers and scar tissue. As might be expected if the damage were the result of injury, the worst damage occurs nearest to the tendon.

Ettema, Amadio, and colleagues suggest that violently or repeatedly moving adjacent fingers in different directions shears connective tissues in the carpal tunnel and leads to carpal tunnel syndrome.

The findings must be confirmed, of course. But if they are, they suggest new treatments for the disabling condition.

In the future, the researchers say, it might be possible to detect early damage in the carpal tunnel and treat it -- perhaps with new drugs -- before carpal tunnel syndrome develops.

Ettema, Amadio, and colleagues report their findings in the November issue of Plastic and Reconstructive Surgery.

SOURCES: Ettema, A.M. Plastic and Reconstructive Surgery, November 2006; vol 118: pp 1413-1422. News release, Mayo Clinic.