Carpal tunnel syndrome

Carpal tunnel syndrome (CTS) is a common condition characterised by symptoms of numbness, pins and needles and sometimes pain affecting the fingers and thumb. The little finger is usually spared. The symptoms are often intermittent, at least at first, and in many cases are worse at night. Activities during the day which involve flexion of the wrist (e.g. driving, holding a telephone, holding a newspaper) can also provoke or exacerbate the symptoms. Occasionally, but not commonly, there is evidence of weakness of muscles at the base of the thumb, which can impair the thumb's ability to oppose against other fingers in the hand.

CTS is caused by compression or pinching of a nerve called the median nerve, which passes into the hand underneath a tough ligament. The nerve is accompanied in this confined space, or tunnel, by nine tendons. Conditions which cause swelling within this space can contribute to the development of CTS - good examples would include rheumatoid arthritis, diabetes and thyroid disorders - but the vast majority of cases do not have an obvious cause (and are therefore called 'idiopathic').

The diagnosis of CTS is often straightforward, but sometimes other diagnoses have to be considered. The median nerve can be compressed elsewhere in the upper limb, and compression of nerve roots in the neck can also cause similar symptoms. It is therefore often helpful to confirm the diagnosis using special tests known as nerve conduction studies and EMGs, which are carried out by a consultant in neurophysiology.

The treatment of this disorder will depend partly on the duration and severity of symptoms. Simple measures such as the use of a splint at night to keep the wrist straight can be extremely helpful, particularly if the symptoms are mainly nocturnal. Steroid injections to the carpal tunnel are occasionally of benefit, especially if the diagnosis is not clear. The definitive treatment for CTS however is operative, and involves division of the ligament which is compressing the median nerve. This operation is known as a 'carpal tunnel release' (CTR) and is a day case procedure.

A carpal tunnel release can be carried out in one of two ways. The standard 'open' technique is usually performed using an injection of local anaesthetic into the palm. An incision of about 4cm is then made to allow direct visualisation of the ligament, which is then divided. The skin is sutured and a bulky dressing is worn on the hand, leaving the fingers and thumb free to move, for 12 to 14 days.

The operation can also be carried out using a minimal access or 'endoscopic' technique. The incision used is much smaller and does not extend onto the palm itself. Recovery is usually quicker and scar tenderness is less of a problem. The ultimate result of the surgery is the same however. This technique requires a general anaesthetic. In some cases it may prove necessary to convert to the standard open technique during the procedure, if adequate visualisation of the nerve and ligament cannot be achieved.

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