Carpel tunnel syndrome is an idiopathic median neuropathy at the carpel tunnel. The carpel tunnel area is located at the end of the wrist. The carpel tunnel is an arch formed by carpel bones in the wrist. The tunnel is about as wide as the thumb and runs from the fold at the wrist to about 2 cm into the palm. Most of the nerves and tendons that control the hand run through this small area of the wrist. If the size of the tunnel is reduced due to swelling, the increased pressure causes numbness of the median nerve and tendons. Left untreated, carpel tunnel syndrome can lead to muscle atrophy of the thumb and palm areas near the thumb.
The predominant symptom of the syndrome is numbness in the thumb, index, middle and radial half of the ring finger. This numbness is most prevalent at night and will wake up the victim of the syndrome. During sleep the wrist flexes in such a way that the syndrome causes this sensation. The areas affected by the syndrome include atrophy of the thenar eminence at the base of the thumb and weakness of the flexor pollicus brevis, opens pollicus, abductor pollicus brevis and decreased sensation of the medial nerve. Sometimes the numbness is perceived as pain due to an incorrect interpretation by the nervous system. Nine flexor tendons and the medial nerve pass through this small area into the hand.
This syndrome was first noted in the late 1800s. It was first identified in literature in 1939, and completely identified in the late 1950s and early 1960s by Dr. George S. Phalen of the Cleveland Clinic. The cause of carpel tunnel syndrome is genetic. Despite common associations with vitamin deficiencies, arthritis or repetitive motion injuries, none of these has been established as a cause of the syndrome. The root cause is decreased area of the tunnel. Some persons have had this area affected by accidents causing damage in the wrist area, but the root cause is genetic. Women have the syndrome 3:1 over men. This makes sense when you consider women have smaller tunnel openings than do men. Women also have a temporary version of this syndrome with most pregnancies which can lead to a more permanent condition in some women.
Diagnosis is made by performing several tests. One is Phalen’s maneuver which involves flexing the wrist gently as far as possible, then waiting for symptoms. If the wrist becomes numb within 60 seconds, the test is positive. The faster the area becomes numb, the worse are the symptoms of the disorder. Other tests used are nerve conduction studies. If carpel tunnel syndrome is present, the medial nerve with conduct impulses significantly slower than the other nerves that supply the hand.
Treatment consists of surgery to bisect the transverse carpel ligament. Cutting through this ligament increases the area of the tunnel and eliminates the pressure on the nerves. Other areas of the body will compensate for the loss of this one ligament. Most people feel this is a good trade off for the end of the numbness in the hand. The surgery is done under local anesthetic and leaves a small incision scar at the wrist area. Other less invasive techniques are being developed to treat this disease. One is a balloon technique that elevates the carpel ligament increasing the area of the tunnel. Other techniques used involve wearing a wrist brace to keep the wrist from flexing during sleep and other activities or the use of cortisone shots to decrease swelling and inflammation in the area.