Carpal tunnel syndrome

What is carpal tunnel syndrome?

Carpal tunnel syndrome is the name given to a condition which results from pressure on a nerve called the median nerve which is in the wrist. This nerve runs down the forearm and across the front of the wrist joint. It carries messages of sensation from the thumb, index and middle fingers to the brain and messages from the brain to some of the muscles of the hand.

Along with some other structures, such as tendons, the nerve runs through a kind of tunnel, called the carpal tunnel, which is made up of a crescent-like formation of wrist bones, with the 'roof' of the tunnel being formed by a band of tough elastic tissue called the flexor retinaculum. This is located just where the hand joins the arm and it is about an inch wide.

For a variety of reasons the pressure in this tunnel can increase causing pressure on the structures that run through it, including the median nerve. This results in the nerve becoming increasingly squashed, causing numbness, tingling and pain in the hand and, in severe cases, weakness of the muscles supplied by the nerve.

What causes carpal tunnel syndrome ?

In most cases the cause of Carpal Tunnel syndrome is unknown although it is thought to be related to the development of inflammation of the tendons leading from the muscles of the arm to the fingers and the wrist. This inflammation causes an increase in pressure around the tendons and therefore an increase in pressure in the carpal tunnel as described above. Causes of this inflammation include repetitive use of the tendons of the fingers and hands such as with keyboard work, knitting or repetitive manual work.

Anything which has a tendency to cause fluid retention or inflammation in the region of the wrist can also predispose to carpal tunnel syndrome. Such conditions include pregnancy, under activity of the thyroid gland or rheumatoid arthritis.

Also, conditions which can reduce the size of the carpal tunnel or which cause pressure to increase inside it are likely to result in carpal tunnel syndrome. For instance wrist fractures, obesity, cysts, swelling or growths within the wrist may all be linked with carpal tunnel syndrome although these last two causes are rare.

What are the symptoms?

The usual symptoms are numbness, tingling and a burning sensation in the hand, especially in the part of the hand nearest the thumb. The pain can sometimes be experienced going up the arm as far as the shoulder. Usually the symptoms are worse at night and can even be bad enough to wake the sufferer up. If the syndrome becomes worse, increasing pressure on the nerve can eventually result in weakness of certain muscles of the hand, especially the muscles of the thumb and index and middle fingers.

How is it diagnosed?

A diagnosis can usually be made from a description of the symptoms given and by examining the hand. This examination may include the doctor trying to reproduce the symptoms by putting the wrist in certain positions or by tapping over the area of the flexor retinaculum. However, in some cases, the doctor may wish to confirm the diagnosis by organising a test called nerve conduction studies. This involves measuring the time taken for a small electric shock to pass along the affected nerve. The speed of progression of the impulse is usually slowed down in carpal tunnel syndrome.

What is the treatment?

The type of treatment recommended will depend on how severe the syndrome is.

Drug treatments and physiotherapy: In mild cases treatment will usually start with a prescription for anti-inflammatory drugs such as Ibuprofen which can dampen down the inflammation in the wrist, or diuretics (water tablets) thus relieving the pressure. If drug treatment does not work the next step maybe to have physiotherapy combined with resting the wrist. This can sometimes be assisted by the use of a wrist splint to prevent any movement of the affected wrist. If symptoms persist the doctor may recommend an injection of hydrocortisone (cortisol) into the wrist in an attempt to reduce the inflammation.

Surgery:In severe or persistent cases, the treatment consists of an operation called carpal tunnel decompression. This involves the surgeon making a small cut about one to two inches long on the front of the wrist running up from the base of the palm of the hand. The tough flexor retinaculum is then cut, thereby relieving the pressure in the wrist. The operation can be performed under general anaesthetic or a type of local anaesthetic. Usually the patient is allowed home the same day although it is important to rest the wrist for a week or two after the operation.

In some hospitals the carpal tunnel release can be performed through an endoscope (a special telescope designed to be inserted into joints). The aim is that by doing it in this way, the risk of wound infection is less since the incision required is much smaller. So far this does seem to be the case although comparison of endoscopic carpal tunnel surgery and traditional surgery seem to suggest that the 'keyhole' method may result in a greater chance of temporary nerve damage.

Medications

Are there complications?

Complications following the operation are rare. The scar may be sore for some time and, if the condition had existed for some time, it may take some weeks or months for the nerve to recover and for the numbness to disappear. In some cases the symptoms may never fully disappear.

Last updated 27 May 2015