Carpal tunnel syndrome is a common condition, affecting women more than men. It is rare in teenagers, quite common during pregnancy but can affect adults of all ages.
One of the main nerves to the hand the 'median nerve', passes through a tunnel at the wrist formed by the curved shape of the bones of the wrist and a tough band of tissue on the palmar surface. Typically the median nerve supplies sensation to the thumb, index, middle and half of the ring finger as shown in the diagram. It supplies a variable number of the small hand muscles especially to the thumb.
The bones of the wrist are known as the carpus and they form a gutter shape. Across the palmar surface is a tough band of tissue, which is known as the flexor retinaculum in the UK or the transverse carpal ligament in the USA; colloquially called the 'roof of the tunnel'.
The cause of carpal tunnel syndrome is multi-factorial. There is an ongoing debate on whether it should be classified as an industrial disease. The following articles give more detail on this issue, both in the UK and across the Atlantic.
Neither the British or American Hand Society consider the condition to be an official industrial disease, however there is no doubt that certain activities seem to make it worse and the posture of the wrist may be critical. It is possible that technique is particularly important and that it behoves anyone with the condition to critically look at the activity, that seems to cause the most symptoms and see if by altering their technique they can control those symptoms.
Whilst there are many potential other causes, the one that must be excluded, particularly in women especially in there 40s and 50s is hypothyroidism (an under-active thyroid gland) and this is easily done by the GP with a simple blood test. Excess weight can be a factor as well. Occasionally inflammation of the flexor tendons ('tenosynovitis') can be the cause.
The classic symptoms described are episodes of numbness and tingling affecting the hand on certain specific activities, such as holding a telephone or book, or when driving. It causes nocturnal disturbance, waking people up and relief is frequently achieved by shaking the hands or hanging them out of the bed. The amount of pain experienced varies enormously from none to intense, almost unbearable pain.
The mainstay of inital treatment is a critical appraisal of activity coupled with physiotherapy. Others include; using wrist splints at night to help the nocturnal symptoms and losing weight is worth a try. In the acute stages a cortisone injection can sometimes help, but the ultimate solution is surgery.