Carpal tunnel syndrome

The tunnel exists in the palm of the hand just beyond the wrist. The small bones of the hand (the carpal bones form the base of the tunnel and a ligament forms the roof. The exact purpose of the ligament is unclear. It probably helps in keeping the tendons and nerves that cross the wrist, together and stop them lifting out of the hand when moving the wrist. Passing through the tunnel are important tendons which move the wrist and fingers and the median nerve. The nerve supplies the small muscles of the thumb (the thenar muscles) and the feeling to the thumb, index, middle and half of the index finger.

The syndrome is the collection of symptoms experienced by a patient who, for whatever reason, has increased pressure inside the tunnel and causes pressure on the median nerve. The nerve responds by not conducting the electrical messages properly and producing a numb or pins and needles type feeling in the fingers. It is common to never actually identify the reason why carpal tunnel syndrome develops in an individual patient. It is usually just the fingers supplied by the nerve but it can be difficult for patients to accurately distinguish exactly which fingers are affected. It is more common in diabetics and pregnant women (where it commonly goes after delivery).

Patients usually start with intermittent tingling in the fingers and often the symptoms are worse at night. They will often wake the patient from sleep and may be eased by shaking the hand vigorously. The symptoms can progress onto more continuous symptoms. Also the muscles that are supplied by the nerve can start to thin down as they are not being used. This is called wasting and affects the small muscles of the thumb.

The diagnosis is a clinical one. This means that the doctor will put the evidence together and make the diagnosis without any special tests. However, if the diagnosis is a little unclear you may be sent for nerve conduction tests. These are electrical tests done with sticky pads on your arm. Electrical signals are sent from pad to pad and areas of poor conductivity can be picked up.

It can be worthwhile changing whatever you think might be bringing on the symptoms but often there is nothing clearly identifiable as the cause. Splints to wear at night can help by keeping the carpal tunnel relatively ‘open’. Your doctor may offer an injection into the carpal tunnel which can relieve the symptoms permanently but more commonly, the symptoms return.

If non-operative measures fail it is reasonable to offer surgical release of the tunnel, called carpal tunnel decompression. This is often done as a day case under local anaesthetic, which means you are awake whilst the surgery is taking place. It is a quick procedure usually only taking about 15 minutes. The skin is cut in the palm over a distance of about 4 or 5 cm and the ligament is exposed. The ligament is cut throughout its whole length so that the median nerve can be seen. The skin is then close over the top but the ligament is not repaired. You will not notice any difference at all in your function of your hand due to the ligament being cut. After the surgery your hand will be wrapped in a bulky ‘boxing-glove’ type bandage and you will be sent home with plans to have your wound checked by medical staff in due course.
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