The median nerve is one of the three major nerves to the hand. It supplies sensation to the palm side of the thumb, and to the index and middle fingers and half of the ring finger. Also, it powers the muscles needed for gripping (fig. 1). This nerve, along with nine tendons to the fingers, passes through a narrow canal (tunnel) bordered on three sides by small bones called carpal bones. On the palm side, it is bordered by a thick fibrous band called the flexor retinaculum (fig. 2).
The symptoms of CTS usually begin at night. A person wakens with numbness, tingling and pain in the hands and forearm. Often this is relieved by shaking the hand. At first these symptoms are intermittent but become more constant as the condition worsens. Next, numbness appears during the day, especially when grasping forcefully or doing repetitive actions with the wrist. As the condition progresses, the hand and wrist become weak, causing clumsiness. The person has a tendency to drop objects. In time, fine motor activities such as grasping zippers and picking up coins become impossible.
These activities have been associated with CTS:
The exact cause of CTS is often difficult to determine. Any condition that increases pressure within the carpal canal can compress and interfere with the blood supply to the median nerve causing symptoms. This may include pregnancy, hypothyroidism, diabetes, swelling of the tendons, fractures to the wrist, cysts and arthritis. Carpal tunnel syndrome is more frequent in women, especially those older than age 45 and who are overweight.
CTS at the workplace is thought to be related to prolonged forceful grasping, awkward wrist posture or the use of heavy, vibrating tools. This is believed to cause tendon swelling and fluid build-up in the canal. Recent studies, however, have failed to relate repetition alone with carpal tunnel syndrome. In fact, the repetitive nature of keyboarding has been found to actually protect one from this condition.
Your doctor may ask you to undergo some tests to rule out the conditions listed above. He may ask for a thyroid test, a test for arthritis, a test of your blood sugar, a test for vitamin B12 deficiency and possibly an x-ray to rule out an abnormal bone or joint.
If the symptoms persist and the other tests are normal, your doctor may refer you to a specialist for a nerve conduction study, considered to be the gold standard for confirming this diagnosis. This test involves the placing of fine pads called electrodes at various points along the wrist and hand. The speed and strength of an electrical impulse as it travels along the median nerve through the carpal tunnel is recorded. If this nerve conduction is slowed across the wrist or carpal tunnel, carpal tunnel syndrome is confirmed.
Non-Surgical - The conservative treatment of carpal tunnel syndrome will improve 50 to 75 per cent of all cases, especially if diagnosed early. This is especially true in most work-related cases. If you suffer from CTS, especially if it is work related, the most important first step is to avoid\ the activities which may aggravate the condition. You should avoid prolonged forceful grasping of tools and other objects, avoid awkward wrist positions and pressure against the palm.
You may be referred to an occupational therapist for the custom fitting of night splints to maintain the hand in an extended (fingers open) position. The night splint is thought to reduce swelling and thus improve the symptoms that occur at night. We normally sleep with our hands closed and flexed and this increases pressure within the wrist. There is no evidence that use of these splints during the day is helpful. Other treatments that your doctor may order include physiotherapy, anti-arthritic medication and occasionally, injection of steroids into the wrist.
Surgical Treatment - If symptoms persist after conservative treatment and the nerve conduction study indicates nerve damage, your doctor may refer you to a surgeon for a surgical release of the fibrous flexor retinaculum at the wrist. Cutting this fibrous band allows an increase in space for the median nerve as it passes though the carpal canal and usually results in immediate improvement in symptoms. The incision extends from the wrist crease down towards the palm and is usually only 2 to 3 centimetres in length. You may be required to wear a splint to protect the wrist for seven to 10 days, at which time the stitches are usually removed. Although the symptoms may improve soon after surgery, the muscle strength may not return for several weeks. Over 90 per cent of cases improve with surgery.
There may be an association, though not yet proven, between Vitamin B6 (pyridoxine) deficiency and the onset of CTS. Vitamin B6 in doses of 100 to 200 milligrams per day for 12 weeks has relieved pain and numbness in some patients. Vitamin C has not been shown to be effective for this purpose. In fact, supplementing with Vitamin C in the presence of a Vitamin B6 deficiency may injure the nerve. The ingestion of high doses of Vitamin B6, greater than 500 milligrams per day, may also injure the nerve.
Carpal tunnel syndrome is not only painful, it has the potential to disable your hand. See your family doctor at the first sign of symptoms. Care at an early stage is crucial to successful treatment and a rapid return to pain-free activity.