What is Carpal Tunnel Syndrome?
Where the wrist and hand meet, nine tendons and one large nerve pass together through a tight tunnel into the palm. This tunnel, called the carpal tunnel, is formed on three sides by the small bones of the wrist and on the fourth side by the very tough fibrous tissue that makes the heel of the hand firm. The nerve passing through the carpal tunnel is called the median nerve. This nerve gives feeling to the thumb, index, middle and part of the ring fingers, and it gives movement to the muscles that lift the thumb away from the palm. Swelling and increased pressure in the carpal tunnel can interfere with the flow of blood to the median nerve. Over time the constriction in blood flow can lead to chronic irritation and eventual damage to the nerve. This problem is called carpal tunnel syndrome.
Chronic irritation of the median nerve can cause a variety of sensations in the hand and forearm including numbness, tingling, burning, sleepiness, pins and needles or even shock-like feelings. The patient's hand may cramp and tire easily or lose strength and dexterity. Feeling may be lost in the thumb, index and middle fingers, and patients may sometimes wake at night with numb or aching hands. Symptoms often occur in both hands.
Carpal tunnel syndrome is diagnosed by evaluating the patient's symptoms, examining the hand and forearm and performing two tests of the electrical functioning of the affected nerves. EMGs (electromyography) detect the irritability of muscles in the hand and arm, and NCVs (nerve conduction velocities) measure the speed of electrical impulses traveling along the median nerve and its branches. EMGs and NCVs can detect significant changes in nerve function and thus confirm a diagnosis of carpal tunnel syndrome.
Treatment of Carpal Tunnel Syndrome
Many patients have mild carpal tunnel syndrome. Treatment in these mild cases may include putting the wrists in splints at night or during the day. People often sleep with their wrists bent forward, which increases the pressure on the nerve by narrowing the size of the carpal canal. Wearing the splints at night and occasionally during the day prevents this. Most patients with more severe carpal tunnel syndrome have abnormal electrical tests though their symptoms may vary from mild to disabling. Some patients with normal tests have severe symptoms that persist for months.
Because nerve damage can be progressive, the appropriate treatment for most patients with abnormal tests or persistent symptoms is carpal tunnel release surgery. In this operation, the tough tissue forming the palmar side of the carpal canal is opened to relieve the pressure on the median nerve. The increased space for the median nerve and tendons results in decreased pressure in the carpal canal and increased blood supply to the median nerve. The nerve then has a chance to heal itself. The surgery itself does not `cure' the nerve. The pattern of symptom relief after carpal tunnel release surgery depends on which of three types of injury the nerve has sustained.
After surgery relieves the pressure, the nerve cells begin growing down the small nerve canals at the rate of about one inch per month. Since the distance from the site of injury to the tips of the fingers is six or seven inches, recovery can take six to eight months after carpal tunnel release surgery. Partial recovery often occurs. About 80 to 90 percent of patients experience good relief from their symptoms after carpal tunnel release surgery. Even those, whose symptoms are not relieved, are still helped because reducing the pressure on the median nerve prevents the problem from becoming worse in most cases. Carpal tunnel release surgery is done on an out-patient basis. No overnight stay in the hospital is necessary. In the procedure most commonly used, an anesthesiologist administers intravenous sedation and the surgeon gives a local anesthesia. This method reduces the risk of the nausea sometimes caused by general anesthesia, and the sedation keeps even very nervous patients comfortable. Sutures remain in the skin for two to three weeks, and patients begin using their hand shortly after surgery.