Carpal tunnel syndrome

Description

Carpal Tunnel Syndrome (CTS) refers to pain, thumb muscle weakness and sensory changes in the hand. Where tendons and the nerve pass through the wrist to the hand, they thread through a canal in the wrist called the carpal tunnel.

When the carpal tunnel becomes narrower as a result of inflammation of the surrounding tissue, the median nerve, causing tingling, numbness and pain in the thumb and index and middle fingers. Prolonged pressure on the median nerve leads to weakness of the thumb muscles.

It appears that the most common cause of this inflammation is repetitive finger or hand movements that strain the wrist, for example typing, playing squash or weightlifting.

Cause

Any condition that causes tissue in the wrist to swell or thicken will increase pressure on the median nerve and cause the symptoms associated with CTS.

Nine tendons pass through the carpal tunnel, each protected by membranes (tendon sheaths). One of the most common causes of pressure on the median nerve is swelling of the tendon sheath due to repeated hand and wrist movements. Anyone whose work calls for long periods of steady hand movement is at risk, from musicians to machinists.

Injuries are especially likely if the work demands repeated grasping, turning and twisting, and even more so if it involves repetitive vibration, as in hammering nails or operating a power tool. A number of sports can bring on symptoms of CTS: rowing, golf, tennis, downhill skiing, archery, competitive shooting and rock climbing are just a few.

Diseases or ailments that cause swelling of the joints and soft tissue, narrowing of the carpal tunnel and compression of nerves include sprains, rheumatoid arthritis, obesity, diabetes, hypothyroidism, leukaemia and menopause.

Broken wrist bones, dislocated bones or new bone growth from healing bones can take up space in the carpal tunnel and put more pressure on the median nerve.

The fluid retention that sometimes accompanies pregnancy can narrow the carpal tunnel, as can tumours or other growths in the wrist (such as a growth on the tendon sheath, called a ganglion).

Symptoms

The most common symptoms of CTS are pain, numbness, tingling, a “pins and needles” sensation and weakness in the hand and fingers. Symptoms may first appear at night, and are most noticeable in the thumb, index finger, middle finger and half of the fourth finger (the fingers controlled by the median nerve). You may experience shooting pains in the wrist or forearm, sometimes extending to the shoulder, as well as difficulty gripping tools or other implements. Symptoms may be worse while sleeping because of the flexed-wrist sleeping position.

As the disease progresses, you may lose all feeling in your fingers, or your strength and ability to grip may be reduced. You may drop objects frequently, lose all strength in your thumb, and be unable to pinch an object between your thumb and forefinger.

With long-lasting CTS, there may be serious and permanent nerve and muscle damage, and the muscles of the thumb may eventually weaken and waste away so that the normal “hill” of muscles at the base of the thumb eventually flattens.

Prevalence

Many people think CTS arrived with the computer keyboard. In fact, injuries to the carpal tunnel and other major nerve passages have been around a long time. CTS affects more women than men, and may affect one or both hands. Women between the ages of 40 and 50 years are most at risk. In this case it usually affects both hands.

Course

The exact duration of CTS is variable, depending on its cause. CTS usually develops gradually. It worsens if you do not stop or change the activities causing the condition.

For example, a person whose CTS is sports-related may recover quickly with early treatment, rest and modified activity. In someone whose CTS is due to chronic arthritis, symptoms may be more stubborn and require longer therapy.

Risk Factors

People who may be at increased risk for CTS include:

• Women near the end of pregnancy (due to fluid retention); women who use birth control pills or those who suffer from pre-menstrual syndrome.
• People with the following conditions could have swelling in the joints or reduced blood flow to the hands. These include rheumatoid arthritis, obesity, diabetes, hypothyroidism, lupus (an auto-immune disease) acromegaly (abnormal body growth due to excess growth hormone).
• Particularly susceptible are people whose work requires repeated forceful movements with the wrist extended, such as using a screwdriver.

When to see a doctor

Call your doctor if:

• You feel pain, numbness or tingling in your fingers that does not go away after two weeks of home treatment
• You have no feeling in your fingers or hand
• You have trouble grasping objects, pinching your thumb and forefinger together, or making a fist
• You have pain and weakness in your hand or arm that is affecting your ability to work

Diagnosis

A diagnosis of CTS is based on an assessment of your history and a physical examination.

Your doctor will ask you about any history of problems with your fingers, hands or wrists, and about current activities at work or home that may be causing your symptoms.

During the physical examination, your doctor will look for swelling, inflammation, a limited range of movement, decreased sensation in your fingers, and muscle weakness in the affected hand.

The classic procedure for identifying CTS is the Phalen wrist flexion test, sometimes called the reverse prayer test. Holding the hands together back to back with fingernails touching induces tingling in a patient suffering from CTS. Most often, non-surgical treatment is prescribed to see if symptoms improve.

If symptoms are more severe, if non-surgical treatment has not improved symptoms, or if symptoms are not clearly due to CTS, further tests may be done to decide which treatment is best.

Tests may include:

• nerve tests to determine the extent of any damage. These involve measuring the speed of electrical impulses as they travel down the nerve. In CTS, the impulse slows as it passes through the carpal tunnel.
• X-rays may be taken in some cases to ascertain if arthritis, broken or dislocated bones or a tumour may be contributing to your symptoms.
• Blood tests (complete blood counts, blood sugar and protein analysis, and thyroid hormone levels) may be done to identify other medical conditions that may be causing symptoms.

Symptoms similar to CTS may also be a result of Raynaud’s disease, a condition in which the skin on your fingers becomes white and then bright red, especially in cold weather.

Treatment

An instinctive reaction to numbness or tingling in the fingers is to drop the hands to the sides and shake the wrists and fingers. This natural response often provides immediate relief and, if the symptoms occur only occasionally, may be all that’s needed. But if you continue the activity that brings on numbness and tingling, the symptoms will continue, and you can suffer permanent damage to the median nerve. The following treatments, ranging from conservative to radical, can help prevent, counteract or cure that damage.

Home

In most cases of CTS, treatment begins with a wrist splint worn mainly at night, rest, cool baths and occasionally cold compresses.

Where your occupation is aggravating your symptoms, your doctor may recommend that you modify your activities to avoid hyperextension of the wrist or putting extra pressure on the median nerve. For example, you may need to change your hand position, use a wrist support in front of your computer keyboard, adjust your chair height, and take frequent breaks to relieve stress. You may want to stop the activity altogether until the symptoms subside.

Simple range-of-motion exercises for fingers and wrists will stretch and strengthen the muscles in the hand and arm, preventing stiffening.

Underlying conditions are treated individually. Fractures can require orthopaedic management. Obese people will be advised regarding weight reduction. Rheumatoid disease is treated with measures directed at the underlying arthritis. Wrist swelling that is associated with pregnancy resolves after delivery of the baby.

Medication

Non-steroidal anti-inflammatory drugs, such as ibuprofen, are most commonly used to decrease inflammation and reduce pain. Reduction of swelling in the wrist relieves pressure on the median nerve in the carpal tunnel, and relieves symptoms of CTS. However, side effects include gastrointestinal upset and even ulceration of the stomach.

These medications should be taken with food and abdominal symptoms should be reported to your doctor.

In more severe cases, your doctor may inject corticosteroids (powerful anti-inflammatory drugs) into the carpal tunnel to reduce pain and inflammation. Relief is rapid but temporary. However, because of the many potentially serious side effects of corticosteroids, they must be used with caution. These drugs can aggravate diabetes and should be avoided in the presence of infections.

Vitamin B6 (pyridoxine) has been reported to relieve some symptoms of CTS, although it has not been shown to be effective in scientific studies. High doses may be harmful.

Surgery

Most patients with CTS improve in response to home treatment and medication. Occasionally, chronic pressure on the median nerve can result in persistent numbness and weakness. In order to avoid serious and permanent nerve and muscle damage, surgical treatment is considered.

The goal of surgery is to reduce pressure on the median nerve. This is done by cutting the transverse carpal ligament (the ligament that forms the top of the carpal tunnel).

The procedure, carpal tunnel release, can be performed with a small-diameter viewing tube called an arthroscope, or in an open-wrist procedure.

After carpal tunnel release, patients often undergo exercise rehabilitation. Although it is uncommon, symptoms can recur. Recovery may take from several weeks to a month or more.

Prevention

If your daily activities involve repetitive finger or hand movements that strain the wrist, you should take steps to prevent CTS.

Take breaks and exercise your hands and wrists every hour. Switch hands and change positions often. Use hand and wrist movements that spread the pressure and motion evenly across your hand and wrist.

If you do a lot of work with computer keyboards, mice and trackballs, make sure you work in a “wrist neutral" position (wrist joint straight, not bent up or down). Several types of aids are available to achieve this, including a cushioned wrist rest, a keyboard tray that adjusts to a position below the work surface, and new, ergonomic keyboards. Use the correct body posture.

Professional assessment of your workstation may be advisable if you continue to have symptoms.

To prevent sports-related CTS, ask your trainer or a sports medicine physician about effective ways to support your wrist during high-risk activities.

Reviewed by Dr Sirk Loots, orthopaedic surgeon.

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