What is it? How does it happen?

The Median Nerve

Carpal tunnel syndrome (CTS) is a condition which results when the median nerve does not work properly. Usually, this is thought to occur because there is too much pressure on the nerve as it runs into the wrist through an opening called the carpal tunnel. It may be easier to understand how this occurs if you understand some of the anatomy of the wrist. The median nerve runs into the hand to supply sensation to the thumb, index finger, long finger, and half of the ring finger. The nerve also supplies a branch to the muscles of the thumb, the carpal tunnel. These muscles help move the thumb and are very important in moving the thumb so that you can touch each of the other fingers. This motion is called opposition.

The carpal tunnel is an opening into the hand that is made up of the bones of the wrist on the bottom and the transverse carpal ligament on the top. Looking at a cross section of the wrist allows one to visualize the anatomy of the carpal tunnel. Through this opening called the carpal tunnel, the median nerve and the flexor tendons run into the hand. Looking a little closer, we see that the median nerve lies just under the transverse carpal ligament.

The flexor tendons are important because they allow us to move the fingers and the hand, such as when we grasp objects. The tendons are covered by a material called tenosynovium. The tenosynovium is very slippery, and allows the tendons to glide against each other as the hand is used to grasp objects. Any condition which causes irritation or inflammation of the tendons can result in swelling and thickening of the tenosynovium. As the tenosynovium covering all of the tendons begin to swell and thicken, the pressure begins to increase in the carpal tunnel - because the bones and ligaments that make up the tunnel are not able to stretch in response to the swelling. Increased pressure in the carpal tunnel begins to squeeze the median nerve against the transverse carpal ligament - because the nerve is the softest structure in the carpal tunnel. Eventually, the pressure reaches a point when the nerve can no longer function normally. Pain and numbness in the hand begins.

One of the first symptoms of carpal tunnel syndrome is numbness in the distribution of the median nerve. This is quickly followed by pain in the same distribution. The pain may also radiate up the arm to the shoulder, and, sometimes the neck. If the condition is allowed to progress, weakness of the thenar muscles can occur. This results in an inability to bring the thumb into opposition with the other fingers and hinders one's grasp.

There are many conditions which can result in irritation and inflammation of the tenosynovium, and eventually cause carpal tunnel syndrome. Different types of arthritis can cause inflammation of the tenosynovium directly. A fracture of the wrist bones may later cause carpal tunnel syndrome if the healed fragments result in abnormal irritation on the flexor tendons. The Key Concept to remember is that anything which causes abnormal pressure on the median nerve will result in the symptoms of pain, numbness and weakness of carpal tunnel syndrome. Recently, physicians have begun to recognize that activities that involve highly repetitive use of the hands can result in carpal tunnel syndrome. This is thought to be caused by inflammation and swelling of the tenosynovium due to overuse.

Exercise Can Help . . .

Wrist Rollers - Strengthen Your Arms While Stretching The Carpal Ligament

A great way to strengthen and stretch the wrist fingers while stretching the transverse carpal ligament is by using a wrist roller. This is a simple exercise you can do at home, with your therapist, or beside your computer.

The idea is to hold your arms out straight in front of your torso with the elbows bent ever so slightly. They should be almost straight and parallel to the floor.

Roll the weight up by turning the handle in such a motion as if you were wringing out a wet washcloth. As the handle is turned the weight will be raised from the floor. Roll the weight to the top position, then slowly unroll it back to the floor.

Try to keep the tension on the weight constant by not allowing the weight to touch the floor, then roll it up and let it down again. You should probably start with 2 ˝ pounds performing 4 repetitions, then work your way up as you get stronger. (One repetition is down, then all the way back up) You will be surprised the burning sensation you will experience in your hands, wrists and forearms.

Once complete, make sure you stretch your hands and swing your arms after each set. This increases the blood flow to your wrists and hands.

This exercise alternates a strong flexion with a strong wrist extension, and this helps to stretch and strengthen the tendons that cross through the carpal tunnel. However, keep the resistance low at first (perhaps a 2 ˝ to 5 pound plate) and slowly increase the resistance over several weeks.

Another benefit is that exercise will increase the blood flow and temperature of the tissue around the tendons and the median nerve. Elevated temperature will make the transverse carpal tunnel more pliable and reduce the pressure on the median nerve. In addition, exercise induced heat can block the pain-conducting properties of some nerve fibers.

It is hard to go wrong with wrist roller exercises, stretching and rest to prevent or relieve CTS and these should be used as a preventative procedure to eliminate the possibility of having future discomfort associated with CTS.

Please consult your physician or therapist before starting this or any other exercise/rehabilitation program. They will be able to design a program most effective for your symptoms.

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	As seen in the June 2000 PT Magazine of Physical Therapy.

References

“Carpal Tunnel Syndrome,” Microsoft® Encarta® Online Encyclopedia 2000
Always PhD FASCM, Steven, (1999). Muscular Development. Hauppauge, New York: Advanced Research Press.
http://dragon.acadiau.ca/~rob/rsi/usflier.html
http://www.sechrest.com/mmg/reflib/ctd/cts/cts.html