CARPAL TUNNEL SYNDROME
What is carpal tunnel syndrome?
Carpal tunnel syndrome is a common condition caused by compression of the median nerve as it passes through a tunnel into the hand. This is usually felt as pain, tingling or numbness in part of the hand, usually the thumb, index and middle fingers. Sometimes the symptoms are felt in the whole hand. The symptoms are often quite variable between individuals but once an individual has symptoms they tend not to vary greatly in quality but may vary in intensity. Thus some people predominantly feel pain and others numbness. The symptoms are typically worse at night and with certain daytime activities such as driving, cycling and reading. The symptoms may be relieved by shaking the hand. One or both hands can be affected. In most people if one hand is affected the will be in due course. Carpal tunnel syndrome can sometimes be caused by pregnancy or injuries, and our research shows it runs in families.
Why does it occur?
The pathology i.e. the abnormality is a lack of blood supply to the nerve. Normally the nerve and finger bending tendons pass through a tunnel across the front of the wrist. The floor and walls of the tunnel are composed of the bones of the wrist joint. The roof of the tunnel is made of a stout fibrous ligament. Normally the pressure in the canal is very low. It increases as the wrist is bent down or back and is most when the wrist is bent fully. Even then the pressure is not normally enough to trouble the nerve. With ageing and associated with various conditions such as wrist fractures (breaks) and pregnancy the background pressure in the wrist increases. Any further increases due to the posture of the wrist then lead to a high enough pressure that the blood supply to the nerve is compromised and it complains with symptoms of pain/numbness and tingling.
What happens if nothing is done?
(This is referred to as the natural history i.e. what happens if Nature runs its own course.)
Some people's symptoms resolve especially if they come on associated with pregnancy. Most people develop gradually increasing symptoms over months to years. Thus the symptoms of pain/numbness will increase and become more intrusive. Most people are particularly troubled by night waking often in the early hours of the morning. If left for too long permanent numbness and muscle weakness and wasting can occur. This reduces hand function considerably.
Making the diagnosis
The Hand specialist who sees the patient will ask questions about their symptoms, when they started, how they progressed, what treatment (if any) they have had and other questions relevant to the problems. They will then examine the patient looking at the wrists and hands and typically also their neck as this can give numbness and tingling in the hands. They may examine other areas such as the elbow depending upon the symptoms described and what they find on clinical examination
What test(s) might be performed?
Tests (also known medically as Investigations) include X-rays, scans, blood tests and particularly in the hand electrical tests (known as EMGs or Neurophysiology). These may be used to help make or confirm a diagnosis after a patient has described their symptoms and been examined.
In Carpal Tunnel Syndrome (CTS) the diagnosis is usually obvious after listening to and examining a patient. If not the commonest test is an electrical test. This is performed at a later date by a specialist (Neurophysiologist). Mild electric shocks are sent up and down the arm and the strength and speed of their conduction is measured. This gives a measure of nerve function. Like all tests it is not completely reliable so it can be normal although the patient has CTS and it can be abnormal when the patient does not have CTS. Your Hand specialist will interpret the results in the light of the previous description of symptoms and examination and advise you accordingly.
Treatment: What are the non-operative treatments?
Treatment should start with non-operative options. These include activity modification (which usually does not give much benefit or has already been tried by the patient), splints and a steroid injection. The splint is mainly worn at night to prevent waking. It stops the wrist from bending down or back too far and so helps protect the nerve from being squeezed at night. An injection of steroid and local anaesthetic can relieve the symptoms at least in the short-term in most people. Typically the relief from injection is temporary so that most surgeons do not recommend it if the symptoms are marked and established. Nonetheless it can be worth a try. Moreover in cases where the clinical picture is unclear a positive response to an injection helps confirm the diagnosis. If the steroid helps for a very long time such as > 1 year or for short-term social reasons e.g. an impending exam or wedding then a second injection may be given but rarely more than two.
If then is any doubt about symptoms coming from the patients neck then neck physiotherapy may be organised.
What does the operation involve?
The operation is called a carpal tunnel release (CTR) or decompression (CTD). The operation is almost always performed with a local anaesthetic, a general anaesthetic is rarely advised. A band, like a blood pressure cuff, is placed around the top of the arm. It is inflated (tightened) during the operation to reduce bleeding, which makes the operation easier and safer. It can be a little uncomfortable, but is almost always well tolerated for the 10 mins or so that it is inflated (this happens just before the surgeons starts the operation). Before that the arm is painted with an antiseptic with a pink dye in it. This is used to help minimise the risk of infection.
The surgeon makes a cut over the front of the wrist, as shown by the red line in the picture. The tight tissue over the nerve is released, so that it has more space in its tunnel. The skin is then stitched up usually with absorbable stitches. A supportive dressing is applied and the patient's arm(s) elevated.
The total time in hospital is usually 1-2 hours.
For most hand conditions surgeons avoid operating on both hands at once as it can be significantly disabling initially. CTR is however commonly performed on both sides at once. This is a decision between the patient and the surgeon.
What happens in the next few weeks?
The care of the hand in the post-operative period is very important in helping to ensure a good result. Initially the aims are comfort and elevation. These are met by keeping the hand up (elevated0 especially in the first few days and by use of a long acting local anaesthetic (Bupivicaine). The local anaesthtic lasts at least 12 hours and sometimes 48 hours. Patients are encouraged start taking painkillers before the pain starts i.e. on return home and for at least 24 hours from there. This way most of our patients report little or any pain.
The bandage can be removed after 2-7 days, leaving a sticky dressing beneath. The patient or GP practice nurse can do this. If well healed at that stage then the wound can be left open (exposed). If in doubt it can be covered with a light dressing for a few more days. The patient is reviewed in clinic between 2-4 weeks following the operation. Typically dissolvable stitches are used so they should not require to be removed.
Your hand can be used for normal activity after the first few days. Most patients can drive after a week or two. Most patients return to work in 2-3 weeks, but this varies with occupation; heavy manual work usually takes about 6 weeks. The wound should be massaged by the patient 3 times a day with a bland soft cream for 3 months once the wound is well healed (typically after 2 weeks). This reduces the scar sensitivity which can be a nuisance. If this is marked a Physio may be organised to help reduce the scar tenderness but this is rarely required. Patients should avoid pressing heavily on the scar for 3 months following the operation as this will be quite painful. Examples of activities to avoid are using the palm to grip/twist a heavy or tight object or use the palm to help get out of a chair.
What are the results of the operation?
At least 85% of patients in studies say they have a good or excellent result following this operation, with relief of the pain and tingling. However, a recent audit of our patients showed >90% good or excellent results at 1 year. Most patients have very rapid or immediate relief of their pain. Symptoms of numbness or weakness may well never resolve particularly if there was continuous numbness or weakness prior to surgery. Nonetheless most patients gain significant benefit in these symptoms which may improve for up to 2 years from surgery.
Are there any risks?
All interventions in medicine have risks. In general the larger the operation the greater the risks. For CTD the risks are small but include:
- The scar may be tender, in about 20% of patients. This usually improves with scar massage, over 3 months.
- Aching, especially on gripping. This occurs in about 4% of patients and also improves with time. Grip strength can also take some months to return to normal.
- Stiffness may occur in particular in the fingers.This is usually short-term and only infrequently requires physiotherapy. But it is very important that it is resolved quickly to avoid permanent stiffness. This occurs rarely but can do associated with CRPS (see below).
- Numbness over the base of the thumb, caused by damage to a branch of the nerve, happens in less than 4% of patients. This rarely causes any functional problems.
- Wound infections occur in about 1% of cases. These usually quickly resolve with antibiotics.
- Chronic Regional Pain Syndrome "CRPS". This is a rare but serious complication, with no known cause or proven treatment. The nerves in the hand "over-react", causing swelling, pain, discolouration and stiffness, which very slowly improve.
- Injury to the main median nerve can occur extremely rarely, resulting in permanent numbness and weakness in the hand.
- Any operation can have unforeseen consequences and leave a patient worse than before surgery. This is rare for CTS.