Repetitive Strain Injury Carpal Tunnel Syndrome

Carpal tunnel syndrome (CTS) is the result of an impairment of the median nerve caused by cumulative trauma through use of the muscles and tendons in and around the carpal tunnel.

CTS can begin with a simple case of muscle overuse in the forearm area. The muscles in the forearm make all hand movements possible. If these forearm muscles are overused and tighten up, the tendons that attach these muscles to the bones in the hand become irritated and inflamed.

Carparl Tunnel Syndrome diagramWhen the flexor tendons in the carpal tunnel become irritated or inflamed, the tenosynovium (the lubricated sheath protecting the tendons) swells, pinching the median nerve against the transverse carpal ligament. The damage to the median nerve generates the symptoms associated with CTS.

CTS can result from problems apparently unrelated to the wrist or forearm. The double crush phenomenon results from damage or pinching of the median nerve at the neck or shoulder area. Nerve compression can result from poor posture or tight muscles in the neck or shoulders. The compression pulls the joints out of working alignment, irritating delicate support tissue and thereby putting pressure on the nerve pathway.

Are There Degrees of CTS?

Some doctors have classified CTS into three levels, based upon degree of suffering as well as method of treatment.

Level 1: Tingling and soreness are reduced by rest or massage. No nerve damage is detected.

Level 2: Symptoms intensify. Orthopedic and neurological tests indicate nerve damage.

Level 3: With severe symptoms, the pain is constant. Doctors recommend total immobilization of the wrist or surgery to relieve the stress on the median nerve.

Common Carpal Tunnel Syndrome Symptoms Sensory:

  • numbness
  • tingling
  • burning
  • coldness
  • pain
  • stiffness.

Motor:

  • loss of hand strength
  • weakness of thumb
  • reduced muscle development in thumbs
  • difficulty holding or pinching items.

Where and What is the Carpal Tunnel?

The wrist bones (bottom) and the transverse carpal ligament (top) create an opening (“tunnel”) in the wrist through which the median nerve and the flexor tendons pass into the hand.

What Does the Median Nerve Do?

The median nerve provides both sensory and motor functions to the hands, conducting sensory information to the central nervous system and movement commands back to the muscles. The median nerve is also responsible for the most critical muscles in the thumb-those that allow the thumb to be opposable, giving it the ability to press against the other fingers.

What Are the Flexor Tendons?

The flexor tendons connect muscle groups in the arm to the bones in the hand and move the fingers and hand. Covered in the lubricating tenosynovium the flexor tendons are able to slide over each other.

What Causes Carpal Tunnel Syndrome?

Theories abound regarding the causes of CTS-vitamin deficiencies, wrist shape, conditions of the neck and spine, posture, overall health, work habits and mental health-but the fact remains that anybody who uses his or her hands in a repetitive motion is susceptible. Regardless of the specific cause, CTS occurs when the tenosynovium becomes inflamed and compresses the median nerve against the bones of the wrist.

Although the specific causes of CTS are not fully known, anything that increases the inflammation of the tenosynovium will aggravate CTS. Proper posture, using wrist rests while typing, and other actions that reduce the irritation of the flexor tendons, may help to alleviate CTS symptoms.

Resources

National Institute of Neurological Disorders and Stroke. (2002). Carpal tunnel syndrome fact sheet.

Health Information Publications. (2003). What is carpal tunnel syndrome (CTS)? Your Medical Source.