Carpal Tunnel Syndrome - Introduction

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• The protective lining of tendons (called the tenosynovium) swells within the carpal tunnel. Some research suggests that this swelling is caused by build-up of fluid (called synovial fluid) under the lining. Synovial fluid lubricates and protects the tendons.
• The transverse ligament, the band of fibrous tissue that forms the roof over the median nerve, becomes thicker and broader.
• The swollen tendons and thickened ligament compress the median nerve fibers, just as stepping on a hose slows the flow of water through it. The effect is to reduce blood flow and oxygen supply to the nerve, slowing the transmission of nerve signals through the carpal tunnel. Some cases of carpal tunnel syndrome may be due to enlargement of the median nerve rather than compression by surrounding tissues.

The result is pain, numbness, and tingling in the wrist, hand, and fingers. Only the little finger is unaffected by the median nerve.

Click the icon to see a depiction of carpal tunnel syndrome.

Review Date: 04/01/2006
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital