Carpal tunnel syndrome (CTS) can also be called median nerve entrapment or median nerve compression.
Symptoms include tingling, burning, or itching and numbness in the palm of the hand and the fingers, especially the thumb and index finger.
CTS is unusual among people aged 20 years or less, the prevalence increases with age, and it is more common among women than men.
The condition is often linked to computer use, but reports date back to the 1800s. It was familiar to orthopedic surgeons since before the widespread use of computers.
Contents of this article:
What is carpal tunnel syndrome?
Carpal tunnel syndrome causes discomfort in the hand and up into the forearm.
The carpal tunnel, also known as the carpal canal, is a narrow, rigid passageway of bones and ligaments at the base of the hand. The median nerve and tendons are also in the carpal tunnel.
The carpal tunnel can sometimes narrow because the tendons become irritated and inflamed, or because of some other swelling that puts pressure on the median nerve.
Sensations to the palm of the hand, the thumb, and three other fingers are controlled by the median nerve. The median nerve does not control the little finger.
The median nerve also controls the muscle that brings the thumb across the palm of the hand to touch the little finger.
Pressure on this nerve can lead to pain, numbness, and weakness in the hand and wrist, and this may cause pain to radiate up the arm and even to the shoulder.
The National Institute of Neurological Disorders and Stroke (NINDS), describe carpal tunnel syndrome as the "most common and widely known of the entrapment neuropathies in which the body's peripheral nerves are compressed or traumatized."
Carpal tunnel syndrome (CTS) affects between 3 percent and 6 percent of adults in the United States. It normally develops in people aged between 45 years and 64 years. It can appear in one or both wrists.
CTS is not a life-threatening condition, but it can have a negative impact on a person's life if left untreated. Eventually, the median nerve can become severely damaged, and there may be permanent numbness in the fingers and permanent weakness in the muscles that are innervated by the median nerve.
Signs and symptoms
Symptoms of CTS tend to develop gradually over time.
The first symptoms often appear during the night, or on waking up in the morning. Patients may feel the need to "shake out" their hands when they wake up. The discomfort may wake them repeatedly during the night.
The three main symptoms associated with CTS are:
These symptoms occur in the thumb and the two fingers next to it, as well as half of the ring finger. They may extend to the rest of the hand and into the forearm.
As the condition progresses, symptoms may persist during the day. The person may lose grip strength and find it harder to form a fist or grasp small objects. Opening a bottle of soda, doing up buttons, or typing on a keyboard can become a challenge.
If left untreated, the muscles at the base of the thumb may wither away, and the person may no longer be able to tell hot from cold with the thumb and finger.
Symptoms tend to emerge or get worse after using the affected hand. The sensation of tingling, burning, and pain may worsen if the arm or hand has been in the same position for a long time.
Causes, tests, and diagnosis
There can be several causes of CTS. It is more likely to develop if the person frequently uses extremes of wrist motion, if they are exposed to vibration, and if they repeatedly use their fingers, for example when typing.
Sometimes CTS is idiopathic, which means no specific cause can be found.
The most common causes of carpal tunnel syndrome are thought to be:
- Repetitive maneuvers
- Repeated use of vibrating hand tools
- Work stress
- Pregnancy, for example, because of edema, or fluid retention
- Inflammatory, degenerative, and rheumatoid arthritis
- Hypothyroidism, or an underactive thyroid
- Trauma, such as dislocation or fracture of the wrist
- Structural problems in the wrist joint
- Lesions in the wrist
- A cyst or tumor in the carpal tunnel
- Overactive pituitary gland
- Any kind of swelling, or inflammation, around the tendons
Researchers have found that a previous wrist fracture and the use of insulin, metformin, and sulphonylureas are associated with a higher chance of CTS. Smoking, hormone replacement therapy (HRT), the combined oral contraceptive pill, and oral corticosteroids did not appear to be not linked to a higher risk of CTS.
One study has suggested that obesity, combined with a square-shaped wrist shape, may increase the likelihood of CTS developing. However, the team concluded that obesity was probably not the cause, because when participants with obesity lost weight, they continued to have CTS.
The same team concluded in other research that the age of women at the menopause may be a factor, and that pregnancy-related hormones may increase the risk of CTS in women at the time of the menopause.
Apart from work-related factors, the main risk for CTS is inflammatory arthritis, but hypothyroidism and diabetes also appear to increase the chance of developing it, according to research published in the Journal of General Internal Medicine.
The National Institute of Neurological Disorders and Stroke (NINDS) say that CTS is three times more likely to occur among people working in assembly operations than in data-entry personnel.
The Canadian Centre for Occupational Health and Safety (CCOHS) list the following occupations as risk factors for CTS:
CTS is linked to repetitive hand movements, but there is no evidence to suggest that computer use is a significant factor.
- Farmers, and specifically those milking cows
- Workers using air-power hand tools
- Assembly-line workers handling objects on the conveyor belt
- Check-out cashiers using laser scanners
- Factory, farm, or mechanical workers who wear tight gloves
- Gardeners weeding by hand
- Locksmiths, turning keys
- Mechanics, using screwdrivers and pushing down ratchets
- Musicians using a bow for a stringed instrument
- Office workers using mouse and keyboard
- Painters who repeatedly use a spray gun
- Poultry or meat processing workers who are deboning and cutting
- Stablehands, painters, and carpenters who press tools into the palm of the hand
Repetitive movements from activities such as knitting can also increase the risk.
Tests for CTS include tapping the wrist lightly to see if this produces a tingling sensation or numbness in the fingers.
Another test is to flex the wrist or hold it above the head for a minute. If there is pain, numbness, or tingling, it may mean that CTS is present.
However, these tests are not conclusive.
A primary care physician is usually able to diagnose carpal tunnel syndrome. They will ask about symptoms and examine the hand and wrist for signs of weakness in the muscles around the thumb. They will also assess the patient's ability to use the hand and wrist.
A number of tests can indicate if a person is likely to have CTS.
Tinel's test, or Tinel's sign: The doctor taps the median nerve at the wrist lightly to see whether the patient feels numbness or tingling in one or more fingers.
Phalen's test for wrist-flexion: The patient presses the backs of the hands against each other so that the wrist is bent. If tingling or numbness occurs within one minute, there may be damage to the median nerve.
Nerve conduction study: Electrodes are placed on the hand and wrist. Small electric shocks are applied. The test measures how quickly the nerves transmit the impulses to the muscles.
Electromyography: A fine needle is inserted into the muscle. Electrical activity on a screen can reveal whether there is any median nerve damage, and if so, how severe it is.
Blood tests: Blood tests can detect an underlying condition that can be related to carpal tunnel syndrome, including hypothyroidism, rheumatoid, arthritis, or diabetes.
Imaging scans: An x-ray can show whether there is a fracture or some other disorder, such as rheumatoid arthritis. An ultrasound scan can check the structure of the median nerve. Studies have found that MRI scans are not useful in diagnosing carpal tunnel syndrome.
Treatment and prevention
Treatment aims to relieve symptoms and slow the progress of CTS by reducing pressure on the median nerve.
Patients with mild symptoms may find their condition improves without any treatment within a few months, especially those aged 30 years or less and pregnant mothers.
The following may help to reduce discomfort:
- Resting the hand and wrist: The more rest the hand and wrist get, the greater the chance of relieving the symptoms.
- Cold compress: Placing an ice pack on the wrist may help when the problem flares up, but ice should not be applied ice directly onto the skin.
- Controlling the triggers: If CTS stems from repetitive hand movements, the person should take breaks so the hand and wrist have time to rest and recover.
- Occupational therapy: A therapist can teach a person how to repetitive tasks differently.
- Wrist splints: These keep the wrist in the same position and prevent it from bending. They can be worn during sleep, but also during the day if they do not interfere with daily activities. Wrist splints are available over the counter at pharmacies. A doctor or pharmacist can advise about the best one to choose.
Most patients with mild symptoms who follow these strategies will notice an improvement within 4 weeks.
The doctor may recommend corticosteroid injections to reduce inflammation. These are normally applied by injection, directly into the carpal tunnel. Tablets are available but they are usually less effective. At first, the pain may increase, but it should start to reduce after 2 days.
If the response is good, but symptoms return after a few months, another dose may be recommended. However, continued use of corticosteroids is not advisable, as there can be long-term adverse effects.
Non-steroidal anti-inflammatory drugs (NSAIDs), such as aspirin or ibuprofen, may help relieve short-term pain. These may only help if the CTS is due to an underlying inflammatory condition, rather than repetitive use.
Other potentially helpful treatments include exercises and botox injections.
A study published in the journal Clinical Rehabilitation found "strong evidence on efficacy of local and oral steroids; moderate evidence that vitamin B6 is ineffective and splints are effective and limited or conflicting evidence that NSAIDs, diuretics, yoga, laser, and ultrasound are effective, whereas exercise therapy and botulinum toxin B injection are ineffective."
In severe cases, where treatments have not been effective and symptoms have lasted for at least 6 months, surgery may be appropriate.
Carpal tunnel release surgery, also called carpal tunnel decompression, is an outpatient procedure. It does not require an overnight stay in the hospital.
Surgery involves cutting the carpal ligament, which is the roof of the carpal tunnel, to reduce pressure on the median nerve.
The Cleveland Clinic estimate that surgery for CTS has a success rate of over 90 percent, and it is rare for the problem to return.
As with any surgery, there is always a risk of complications, including infection, post-operative bleeding, nerve injury, and scarring.
Measures to reduce the risk of developing CTS include:
Cold makes symptoms worse, so wearing gloves in winter can help.
- Not gripping too hard when performing manual tasks
- Not overbending the wrist, for example, all the way down or up
- Sleeping and working with the wrists straight
- Avoiding repeated flexing and extending of the wrists
- Maintaining correct posture to prevent putting undue strain on the wrist and hands
- Redesigning the workstation to reduce unnatural and awkward wrist positions
- Resting and taking frequent breaks when performing routine tasks to protect against the long-term effects
- Keeping the hands warm by wearing gloves in a cold environment, as having cold hands can increase the risk of developing CTS
- Treating any underlying conditions, for example, establishing good glucose control to help prevent the complications of diabetes
According to the National Library of Medicine, there is no evidence that using a computer increases the risk of CTS, but ergonomic keyboards with an elevated and curved keyboard may reduce strain by helping to keep the hands in a neutral position.
Some people recommend hand movement exercises, including yoga, and massages, but research has not confirmed that these are effective.