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Carpal Tunnel syndrome

What is carpal tunnel syndrome?

Carpal tunnel syndrome is a condition characterized by pain, numbness and possible weakness in the hand because of compression of the median nerve at the wrist (the carpal tunnel).

What causes carpal tunnel syndrome?

The median nerve supplies feeling to our thumb, index , middle and half of the ring finger. It also supplies the small muscles around the thumb in the hand via the motor branch. This nerve runs together with the flexor tendons in a tight compatment across the wrist called the carpal tunnel.  This tunnel is formed by the bones in our wrist and a thick ligament called the transverse carpal ligament. Because of  this tight structure forming the tunnel there is very little space available to accommodate any changes to the contents of the tunnel.  Thus the pressure in the tunnel increases and the nerve becomes compressed.

There are many 2ndry causes that alter the structure and contents of the tunnel and such as synovitis or previous trauma to the wrist. However in most cases of carpal tunnel syndrome there is no identifiable cause. There are strong associations with diabetes and carpal tunnel syndrome. Females are also more prone to get carpal tunnel syndrome and the most common age group is between 45-70yrs.

Much has been written about certain occupations specifically causing carpal tunnel syndrome but there is little evidence to support such claims. It is more likely that certain patients have other features that increase the chances of developing carpal tunnel syndrome and the workplace is only one of several risk factors that contribute to a patient developing the condition. Ergonomics in the workplace has been acknowledged as being a contributory factor in the development of carpal tunnel syndrome.

Do I have carpal tunnel syndrome?

Early signs of carpal tunnel syndrome are pins and needles in the thumb, index and middle fingers. This often presents at night or wakes you up because of the pain associated with the nerve compression. The reason for night pain and numbness is because we tend to sleep with our wrists bent which increases the pressure on the nerve.

Other features of carpal tunnel syndrome are worsening of the numbness when driving, holding books or tablets and otherwise using the hand. Sometimes the hand is clumsy because of both numbness and weakness. Using the hand for activities of daily living becomes difficult. Importantly the little finger should not be involved as it is supplied by a different nerve, the ulnar nerve which does not run through the carpal tunnel.

In severe cases you may notice wasting of the muscles of the hand around the thumb. This indicates severe long standing compression and should be dealt with quickly.

Persistent numbness in the hand should be investigated and acted upon. Carpal tunnel syndrome is largely a clinical diagnosis with a typical history. Investigations such as nerve conduction studies can assist in making the diagnosis in atypical cases.

A local steroid injection next to the median nerve at the wrist is a useful test to identify CTS. It has the benefit of providing temporary symptomatic relief to patients for a few weeks. Only about 10% of patients will be “cured” with a local steroid injection.

How do you treat carpal tunnel syndrome?

Mild intermittent symptoms can be observed. If night time is a problem, night splints can be prescribed which may alleviate the symptoms.

Workplace ergonomics should be addressed if these are suspected of playing a causative role in the CTS.

Secondary causes of CTS such as diabetes or thyroid abnormalities should be considered.

Persistent or progressive symptoms of carpal tunnel syndrome should be treated. The only “cure” for the above presentation is surgery. Surgery involves dividing the ligament that forms the roof of the tunnel which releases the pressure on the nerve. This is performed as a day case under regional or general anaesthesia.

Surgery is about 85% successful in treating CTS. Reasons for failed surgery include an incorrect diagnosis or possible “double crush” of the nerve. This is where there is another problem with the nerve elsewhere such as a pinched nerve in the neck. Diabetic damage to the nerve itself can co-exist with carpal tunnel syndrome. The response to surgery can be unpredictable in these situations.

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