You're working at your desk, trying to ignore the tingling or numbness you've had for some time in your hand and wrist. Suddenly, a sharp, piercing pain shoots through the wrist and up your arm. Just a passing cramp? It could be carpal tunnel syndrome.

The carpal tunnel is a narrow passageway of ligament and bones at the base of your hand. It contains nerve and tendons. Sometimes, thickening from irritated tendons or other swelling narrows the tunnel and causes the nerve to be compressed. Symptoms usually start gradually. As they worsen, grasping objects can become difficult.

Often, the cause is having a smaller carpal tunnel than other people do. Other causes include performing assembly line work, wrist injury, or swelling due to certain diseases, such as rheumatoid arthritis. Women are three times more likely to have carpal tunnel syndrome than men.

Early diagnosis and treatment are important to prevent permanent nerve damage. Your doctor diagnoses carpal tunnel syndrome with a physical exam and special nerve tests. Treatment includes resting your hand, splints, pain and anti-inflammatory medicines, and sometimes surgery.

Carpal tunnel syndrome (CTS) occurs when the median nerve, which runs from the forearm into the palm of the hand, becomes pressed or squeezed at the wrist. The carpal tunnel—a narrow, rigid passageway of ligament and bones at the base of the hand—houses the median nerve and the tendons that bend the fingers. The median nerve provides feeling to the palm side of the thumb and to the index, middle, and part of the ring fingers (although not the little finger). It also controls some small muscles at the base of the thumb.

Sometimes, thickening from the lining of irritated tendons or other swelling narrows the tunnel and compresses the median nerve. The result may be numbness, weakness, or sometimes pain in the hand and wrist (some people may feel pain in the forearm and arm). CTS is the most common and widely known of the entrapment neuropathies, in which one of the body’s peripheral nerves is pressed on or squeezed.

Carpal Bones

The wrist and base of the hand are formed by a series of eight small carpal bones (see Figure 8.7). The carpal bones are arranged in two rows, forming a proximal row of four carpal bones and a distal row of four carpal bones. The bones in the proximal row, running from the lateral (thumb) side to the medial side, are the scaphoid (“boat-shaped”), lunate (“moon-shaped”), triquetrum (“three-cornered”), and pisiform (“pea-shaped”) bones. The small, rounded pisiform bone articulates with the anterior surface of the triquetrum bone. The pisiform thus projects anteriorly, where it forms the bony bump that can be felt at the medial base of your hand. The distal bones (lateral to medial) are the trapezium (“table”), trapezoid (“resembles a table”), capitate (“head-shaped”), and hamate (“hooked bone”) bones. The hamate bone is characterized by a prominent bony extension on its anterior side called the hook of the hamate bone.

A helpful mnemonic for remembering the arrangement of the carpal bones is “So Long To Pinky, Here Comes The Thumb.” This mnemonic starts on the lateral side and names the proximal bones from lateral to medial (scaphoid, lunate, triquetrum, pisiform), then makes a U-turn to name the distal bones from medial to lateral (hamate, capitate, trapezoid, trapezium). Thus, it starts and finishes on the lateral side.

Figure 8.7 Bones of the Wrist and Hand The eight carpal bones form the base of the hand. These are arranged into proximal and distal rows of four bones each. The metacarpal bones form the palm of the hand. The thumb and fingers consist of the phalanx bones.

The carpal bones form the base of the hand. This can be seen in the radiograph (X-ray image) of the hand that shows the relationships of the hand bones to the skin creases of the hand (see Figure 8.8). Within the carpal bones, the four proximal bones are united to each other by ligaments to form a unit. Only three of these bones, the scaphoid, lunate, and triquetrum, contribute to the radiocarpal joint. The scaphoid and lunate bones articulate directly with the distal end of the radius, whereas the triquetrum bone articulates with a fibrocartilaginous pad that spans the radius and styloid process of the ulna. The distal end of the ulna thus does not directly articulate with any of the carpal bones.

The four distal carpal bones are also held together as a group by ligaments. The proximal and distal rows of carpal bones articulate with each other to form the midcarpal joint (see Figure 8.8). Together, the radiocarpal and midcarpal joints are responsible for all movements of the hand at the wrist. The distal carpal bones also articulate with the metacarpal bones of the hand.

Figure 8.8 Bones of the Hand This radiograph shows the position of the bones within the hand. Note the carpal bones that form the base of the hand. (credit: modification of work by Trace Meek)

In the articulated hand, the carpal bones form a U-shaped grouping. A strong ligament called the flexor retinaculum spans the top of this U-shaped area to maintain this grouping of the carpal bones. The flexor retinaculum is attached laterally to the trapezium and scaphoid bones, and medially to the hamate and pisiform bones. Together, the carpal bones and the flexor retinaculum form a passageway called the carpal tunnel, with the carpal bones forming the walls and floor, and the flexor retinaculum forming the roof of this space (Figure 8.9). The tendons of nine muscles of the anterior forearm and an important nerve pass through this narrow tunnel to enter the hand. Overuse of the muscle tendons or wrist injury can produce inflammation and swelling within this space. This produces compression of the nerve, resulting in carpal tunnel syndrome, which is characterized by pain or numbness, and muscle weakness in those areas of the hand supplied by this nerve.

Figure 8.9 Carpal Tunnel The carpal tunnel is the passageway by which nine muscle tendons and a major nerve enter the hand from the anterior forearm. The walls and floor of the carpal tunnel are formed by the U-shaped grouping of the carpal bones, and the roof is formed by the flexor retinaculum, a strong ligament that anteriorly unites the bones.

What is carpal tunnel syndrome?

Carpal tunnel syndrome (CTS) occurs when the median nerve, which runs from the forearm into the palm of the hand, becomes pressed or squeezed at the wrist. The carpal tunnel is a narrow, rigid passageway of ligament and bones at the base of the hand that houses the median nerve and the tendons that bend the fingers. The median nerve provides feeling to the palm side of the thumb and to most of the fingers. Symptoms usually start gradually, with numbness, tingling, hand weakness, and sometimes pain in the hand and wrist. CTS makes it difficult for some people to drive, read a book, grasp small objects, or do other tasks. Sometimes no direct cause of CTS can be found; contributing factors include trauma or injury to the wrist that causes swelling, as well as thyroid disease, rheumatoid arthritis, and fluid retention during pregnancy. Women are three times more likely than men to develop carpal tunnel syndrome. The disorder usually occurs only in adults.

Is there any treatment?

Initial treatment generally involves wearing a splint at night to keep the wrist from bending, over-the-counter and prescription drugs including non-steroidal anti-inflammatory drugs to temporarily reduce swelling and ease pain, and injections of corticosteroid drugs (such as prednisone). For more severe cases, surgery may be recommended. Underlying causes such as diabetes or arthritis should be treated first. Alternative therapies such as yoga can reduce pain and improve grip strength in some people with CTS.

What is the prognosis?

In general, carpal tunnel syndrome responds well to treatment, but less than half of individuals report their hand(s) feeling completely normal following surgery. Some residual numbness or weakness is common. Most people may need to modify work activity for several weeks following surgery. Stretching exercises, taking frequent rest breaks, wearing splints to keep wrists straight, and using correct posture and wrist position can help prevent or worsen symptoms. Making changes in the workplace may help but may not prevent the occurrence of carpal tunnel syndrome.

Women are three times more likely than men to develop carpal tunnel syndrome. People with diabetes or other metabolic disorders that directly affect the body’s nerves and make them more susceptible to compression are also at high risk. CTS usually occurs only in adults.

Workplace factors may contribute to existing pressure on or damage to the median nerve. The risk of developing CTS is not confined to people in a single industry or job, but may be more reported in those performing assembly line work—such as manufacturing, sewing, finishing, cleaning, and meatpacking—than it is among data-entry personnel.

Carpal tunnel syndrome is often the result of a combination of factors that increase pressure on the median nerve and tendons in the carpal tunnel, rather than a problem with the nerve itself. Contributing factors include trauma or injury to the wrist that cause swelling, such as sprain or fracture; an overactive pituitary gland; an underactive thyroid gland; and rheumatoid arthritis. Other factors that may contribute to the compression include mechanical problems in the wrist joint, repeated use of vibrating hand tools, fluid retention during pregnancy or menopause, or the development of a cyst or tumor in the canal. Often, no single cause can be identified.

Symptoms usually start gradually, with frequent numbness or tingling in the fingers, especially the thumb and the index and middle fingers. Some people with CTS say their fingers feel useless and swollen, even though little or no swelling is apparent. The symptoms often first appear in one or both hands during the night. The dominant hand is usually affected first and produces the most severe symptoms. A person with CTS may wake up feeling the need to “shake out” the hand or wrist. As symptoms worsen, people might feel tingling during the day, especially with certain activities such as talking on the phone, reading a book or newspaper, or driving. Hand weakness may make it difficult to grasp small objects or perform other manual tasks. In chronic and/or untreated cases, the muscles at the base of the thumb may waste away. Some people with very severe CTS cannot determine between hot and cold by touch, and may burn their fingertips without knowing it.

Do you have tingling or numbness in your hand or fingers? It could be a sign that you have carpal tunnel syndrome. Often, you’ll get pain in your thumb, index, and middle finger. You may find that your hands are clumsy, and it’s harder to grip things.

Symptoms of carpal tunnel usually start slowly. Many people first notice the signs overnight because they sleep with their wrists bent. As time goes on, that tingling or numbness may last through the day as well.

Carpal tunnel syndrome occurs when one of the main nerves in your forearm, called the median nerve, is squeezed or compressed.

“That nerve is really important in the function of the hand,” says Dr. Kevin Chung, chief of hand surgery at the University of Michigan. It gives sensation to the palm side of your thumb, index, middle finger, and part of the ring finger. It also moves some of your hand muscles.

“It can become trapped in the very tight space that goes through your wrists,” he says. “That space is known as the carpal tunnel.”

Carpal tunnel syndrome is usually caused by a combination of factors that shrink this space. The heavy, repetitive work of certain jobs can contribute to carpal tunnel syndrome. It’s common to people who work in meat-packing plants or perform intense assembly line work. Injury to the wrist can also cause swelling that compresses the median nerve.

But it’s often unclear why some people develop carpal tunnel syndrome. People who have rheumatoid arthritis or an underactive thyroid gland are more likely to develop carpal tunnel syndrome. Fluid retention during pregnancy or menopause can also contribute.

To treat the issue, doctors will first try splinting the wrist. This limits movement and helps reduce pressure on the nerve. Sometimes splints are only worn at night. During the day, experts recommend taking breaks from tasks that put stress on your hands. Over-the-counter pain relievers can help manage the discomfort.

For more tips that may help relieve carpal tunnel symptoms, see the Wise Choices box. If these steps don’t improve the condition, it may be time to turn to surgery.

“Surgery is necessary when the patient has persistent numbness of the hand and when the muscles stop working because the nerve is not functioning well,” says Chung.

Carpal tunnel surgery is one of the most common surgeries in the U.S. It involves dividing the ligaments—bands of elastic tissue—that support the wrist to reduce pressure on the median nerve. These ligaments usually grow back after surgery in a way that gives the nerve more room. The surgery only takes about 10 to 30 minutes.

“Relief can be quite immediate, between one to two weeks,” says Chung. “But it depends on how badly the nerve was compressed and for how long.”

Some strategies, like stretching your hands and wearing fingerless gloves, may help prevent carpal tunnel syndrome. But research hasn’t proven that these approaches work.

Many conditions can mimic carpal tunnel symptoms, so it’s important to go to a medical professional with expertise in the condition.

“Carpal tunnel syndrome can be disabling. It is so important that patients choose a surgeon wisely,” says Chung. He recommends choosing a board-certified hand surgeon trained to diagnose and treat carpal tunnel.

Carpal Tunnel Relief

These strategies may provide short-term relief from carpal tunnel syndrome:

• Take frequent breaks from repetitive physical activities.
• Apply cool packs if the wrist is red, warm, and swollen.
• Be sure to use correct posture and wrist position.
• Wear a brace at night to keep wrists straight while asleep.
• Take over-the-counter medicines that reduce swelling.

Early diagnosis and treatment are important to avoid permanent damage to the median nerve.

• A physical examination of the hands, arms, shoulders, and neck can help determine if the person’s complaints are related to daily activities or to an underlying disorder. A physician can rule out other conditions that mimic carpal tunnel syndrome. The wrist is examined for tenderness, swelling, warmth, and discoloration. Each finger should be tested for sensation and the muscles at the base of the hand should be examined for strength and signs of atrophy.
• Routine laboratory tests and X-rays can reveal fractures, arthritis, and nerve-damaging diseases such as diabetes.
• Specific tests may produce the symptoms of CTS. In the Tinel test, the doctor taps on or presses on the median nerve in the person’s wrist. The test is positive when tingling in the fingers or a resultant shock-like sensation occurs. The Phalen, or wrist-flexion, test involves having the person hold his or her forearms upright by pointing the fingers down and pressing the backs of the hands together. Carpal tunnel syndrome is suggested if one or more symptoms, such as tingling or increasing numbness, is felt in the fingers within 1 minute. Doctors may also ask individuals to try to make a movement that brings on symptoms.
• Electrodiagnostic tests may help confirm the diagnosis of CTSs. In a nerve conduction study, electrodes are placed on the hand and wrist. Small electric shocks are applied and the speed with which nerves transmit impulses is measured. In electromyography, a fine needle is inserted into a muscle; electrical activity viewed on a screen can determine the severity of damage to the median nerve.
• Ultrasound imaging can show abnormal size of the median nerve. Magnetic resonance imaging (MRI) can show the anatomy of the wrist but to date has not been especially useful in diagnosing carpal tunnel syndrome.

Treatments for carpal tunnel syndrome should begin as early as possible, under a doctor's direction. Underlying causes such as diabetes or arthritis should be treated first.

Non-surgical treatments

• Splinting. Initial treatment is usually a splint worn at night.
• Avoiding daytime activities that may provoke symptoms. Some people with slight discomfort may wish to take frequent breaks from tasks, to rest the hand. If the wrist is red, warm and swollen, applying cool packs can help.
• Over-the-counter drugs. In special circumstances, various medications can ease the pain and swelling associated with carpal tunnel syndrome. Nonsteroidal anti-inflammatory drugs (NSAIDs), such as aspirin, ibuprofen, and other nonprescription pain relievers, may provide some short-term relief from discomfort but haven’t been shown to treat CTS.
• Prescription medicines. Corticosteroids (such as prednisone) or the drug lidocaine can be injected directly into the wrist or taken by mouth (in the case of prednisone) to relieve pressure on the median nerve in people with mild or intermittent symptoms. (Caution: individuals with diabetes and those who may be predisposed to diabetes should note that prolonged use of corticosteroids can make it difficult to regulate insulin levels.)
• Alternative therapies. Acupuncture and chiropractic care have benefited some individuals but their effectiveness remains unproved. An exception is yoga, which has been shown to reduce pain and improve grip strength among those with CTS.

Surgery

Carpal tunnel release is one of the most common surgical procedures in the United States. Generally, surgery involves severing a ligament around the wrist to reduce pressure on the median nerve. Surgery is usually done under local or regional anesthesia (involving some sedation) and does not require an overnight hospital stay. Many people require surgery on both hands. While all carpal tunnel surgery involves cutting the ligament to relieve the pressure on the nerve, there are two different methods used by surgeons to accomplish this.

• Open release surgery, the traditional procedure used to correct carpal tunnel syndrome, consists of making an incision up to 2 inches in the wrist and then cutting the carpal ligament to enlarge the carpal tunnel. The procedure is generally done under local anesthesia on an outpatient basis, unless there are unusual medical conditions.
• Endoscopic surgery may allow somewhat faster functional recovery and less postoperative discomfort than traditional open release surgery but it may also have a higher risk of complications and the need for additional surgery. The surgeon makes one or two incisions (about ½ inch each) in the wrist and palm, inserts a camera attached to a tube, observes the nerve, ligament, and tendons on a monitor, and cuts the carpal ligament (the tissue that holds joints together) with a small knife that is inserted through the tube. Following the surgery, the ligaments usually grow back together and allow more space than before. Although symptoms may be relieved immediately after surgery, full recovery from carpal tunnel surgery can take months. Some individuals may have infections, nerve damage, stiffness, and pain at the scar. Almost always there is a decrease in grip strength, which improves over time. Most people need to modify work activity for several weeks following surgery, and some people may need to adjust job duties or even change jobs after recovery from surgery.

Recurrence of carpal tunnel syndrome following treatment is rare. Less than half of individuals report their hand(s) feeling completely normal following surgery. Some residual numbness or weakness is common.

At the workplace, workers can do on-the-job conditioning, perform stretching exercises, take frequent rest breaks, and use correct posture and wrist position. Wearing fingerless gloves can help keep hands warm and flexible. Workstations, tools and tool handles, and tasks can be redesigned to enable the worker’s wrist to maintain a natural position during work. Jobs can be rotated among workers. Employers can develop programs in ergonomics, the process of adapting workplace conditions and job demands to the capabilities of workers. However, research has not conclusively shown that these workplace changes prevent the occurrence of carpal tunnel syndrome.

The mission of the National Institute of Neurological Disorders and Stroke (NINDS) is to seek fundamental knowledge of the brain and nervous system and to use that knowledge to reduce the burden of neurological disease. The NINDS is a component of the National Institutes of Health (NIH), the leading supporter of biomedical research in the world.

Scientists supported by the NINDS are studying the factors that lead to long-lasting neuropathies, and how the affected nerves are related to symptoms of pain, numbness, and functional loss. Researchers also are examining biomechanical stresses that contribute to the nerve damage responsible for symptoms of carpal tunnel syndrome in order to better understand, treat, and prevent this ailment. By quantifying the distinct biomechanical pressures from fluid and anatomical structures, researchers are finding ways to limit or prevent CTS in the workplace and decrease other costly and disabling occupational illnesses.

Scientists funded through NIH’s National Center for Complementary and Integrative Health are investigating the effects of acupuncture on pain, loss of median nerve function, and changes in the brain associated with CTS. In addition, a randomized clinical trial designed to evaluate the effectiveness of osteopathic manipulative treatment in conjunction with standard medical care is underway. Evaluations of these therapies and other therapies will help to tailor individual treatment programs.

Another NIH component, the National Institute of Arthritis and Musculoskeletal and Skin Disorders (NIAMS), supports research on tissue damage associated with repetitive motion disorders, including CTS. Among other research, scientists have developed animal models that are helping to understand and characterize connective tissue in hopes of reducing harmful tissue buildup and identifying new treatments.

More information about carpal tunnel syndrome research supported by NINDS and other NIH Institutes and Centers can be found using NIH RePORTER (projectreporter.nih.gov), a searchable database of current and past research projects supported by NIH and other federal agencies. RePORTER also includes links to publications and resources from these projects.