Carpal Tunnel Syndrome (CTS) is a condition caused by mechanical interference with the median nerve at the wrist. This large nerve provides feeling to the thumb, index and middle fingers and half of the ring finger, and also provides the power to the small muscles at the base of the thumb. It enters the hand having coursed its way down the forearm, by passing beneath a tough ligament (the carpal ligament) that runs across the wrist from side to side. For reasons that are poorly understood the nerve may become squeezed, either because the contents of the tunnel beneath the ligament swell, or because the size of the tunnel decreases. Since the tunnel contains many tendons and is formed by the ligament itself and the bones of the wrist (on the other three walls of the tunnel) there are many potential reasons for swelling that could compress the nerve.
Known conditions that can exacerbate or result in CTS include diabetes, arthritis, thyroid disease, pregnancy and obesity. Some forms of trauma and some vibration related conditions may also cause the condition and some occupations have a particular predisposition to carpal tunnel syndrome, probably as a result of the wrist position.
The symptoms of CTS vary in intensity and nature. Most patients first notice some tingling in the fingers supplied by the median nerve (especially often, the long finger) which may be accompanied by numbness. This is often worse at night, and may be disturbing enough to wake the patient from sleep, and is particularly noticeable in the mornings. On waking, patients may find their hand numb or unusually clumsy. Pain is a late feature of the condition and is often hard to localise: it may be felt in the hand or forearm or even in the upper arm and shoulder, and is again usually worse at night, when it may be relieved typically by hanging the hand down or shaking it.
Diagnosis is usually made on clinical grounds and most patients present such a clear cut picture that laboratory tests of the nerves (Nerve Conduction Studies) are not required. However in some cases neurophysiology helps to define the condition, and also to exclude other nerve afflictions that might confuse the diagnosis. Your doctor may also run some simple blood tests to exclude thyroid disease or other causes (mentioned above) of CTS. Correction of these may ameliorate symptoms without further treatment, as may weight loss in cases of obesity.
Treatment has three main options. Conservative treatment addresses any underlying condition (as above), and can be combined with splinting of the wrist to relieve the pressure in the tunnel. This is usually with the wrist slightly extended (bent slightly back) and is commonly achieved with a Futura splint. This may alleviate symptoms sufficiently to avoid further treatment, and is especially useful in pregnancy when resolution of symptoms can be expected in many patients after delivery.
Injection of the carpal tunnel with a long acting steroid (triamcinolone is the preparation I favour) is useful in mild cases and can result in complete resolution of symptoms. I have found that this is less likely if the patient is waking regularly at night with pain, and even after injections the symptoms in about half the patients eventually return. Injection is very safe but repeat injection has some risks as the steroid does eventually weaken tendon structures. Also, inadvertent injection INTO the nerve can result in severe nerve damage. For this reason I am reluctant to inject a carpal tunnel more than twice.
Surgery is simple and generally effective. the aim is to divide the ligament, allowing it to relax and so relieving pressure on the nerve. There are a number of ways of achieving this and your surgeon will discuss the options with you. I prefer where possible to do this simple procedure under local anaesthetic, (in an operation lasting only a few minutes) and to discharge the patient immediately afterwards with only a small sticky plaster on the short scar at the wrist.
The results of this operation are usually good. Pain is almost always immediately relieved, and the tingling is also relieved. Some numbness may persist if the hand has been affected for a long time and this may be slow to recede, sometimes taking many weeks. Any loss of muscle bulk that has occurred is unlikely to improve.
Complications can occur after any surgery and include unexpected bleeding, wound infection and lumpy or painful scars. In this procedure an additional 2 risks should be recorded: the nerve may inadvertently not be completely released and so symptoms may not improve or rarely may get worse, or the nerve beneath the ligament may be injured, truly an avoidable complication.
However these are extremly rare eventualities and the vast majority of patients get great relief from this simple safe procedure.
Professor Simon Kay, Consultant Plastic Surgeon
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