Anatomy

At the base of the palm is a tight canal or gap formed by the wrist bones (the carpal bones) and the tough membrane that holds the bones together (the transverse carpal ligament). This gap is called the carpal tunnel. Through this gap the median nerve, running from the shoulder to the hand, must pass. The carpal tunnel is quite snug and there is just enough room for the median nerve and the flexor tendons that allow us to move the fingers of our hand. If anything takes up extra room in the canal, such as swelling of tissues, the median nerve becomes compressed and carpal tunnel syndrome results.

Symptoms

The symptoms of carpal tunnel syndrome include 'paraesthesia' (numbness or pins and needles) of the thumb, index and middle fingers. These symptoms commonly occur during the night or while using the hand for activities such as driving, writing, tying laces, sweeping, opening a sealed jar etc. There may also be sensation of pain that can radiate up the arm to the shoulder. If the condition is allowed to progress weakness of the hand can occur. In severe cases the muscles forming the ball of your thumb can diminish in size (muscle wasting).

What causes carpal tunnel syndrome?

Carpal tunnel syndrome is one of the most common musculoskeletal problems and affects up to 1 in 20 people. In most cases, there is no specific cause for the carpal tunnel syndrome.

There are certain situations where various trigger factors may cause the symptoms to develop. Conditions associated with carpal tunnel syndrome include pregnancy, rheumatoid arthritis and diabetes mellitus. Injury or trauma to the wrist area can also cause swelling of the tissues and compression of the median nerve. Repetitive movements of the wrist such as in squash, knitting, typing, writing, use of hand tools and similar activities may cause this condition. Occasionally it runs in families where an inherited small bone structure may lead to increased incidence of carpal tunnel syndrome.

Progress of carpal tunnel syndrome

The progress of carpal tunnel syndrome is usually predictable. First, the sensory symptoms (numbness) occur due to involvement of the sensory nerve fibres before any involvement (weakness or wasting) of the larger motor nerve fibres.

If the pressure on the nerve is relieved early enough, the symptoms rapidly disappear. If symptoms are ignored too long the continued pressure on the nerve can cause irreversible or permanent nerve damage.

Investigation

A suspected case of carpal tunnel syndrome is usually diagnosed with nerve conduction studies. These need to be ordered by a medical practitioner and the results generally take two to three days to be sent to the requesting doctor. All patients contemplating surgery should have pre-operative nerve conduction studies.

MRI and ultrasound scans can be performed of the carpal tunnel region however, these are not diagnostic by themselves.

Treatment

Treatment of this condition is either with medical (drug) therapy or surgery. Rarely where there is a distinct cause; the symptoms may disappear with the removal of the triggering factor. The commonest such situation is where the carpal tunnel occurs during pregnancy. The symptoms often, but not always, resolve after the baby is delivered.

The only medical therapies proven to be effective are oral steroid tablets or local steroid injection. While these may provide short-term relief, their long-term effect is unknown. Furthermore both therapies have significant side effects that need to be considered. Your family physician can advise you further on such treatments.

Surgical treatment is effective and most cases eventually require surgery. There are several different types of surgery available for this problem. Any patient considering this treatment needs to discuss the risks and benefits of surgery with their treating doctor or surgeon.

In general terms, any surgery is done as an 'day case' procedure (i.e. the patient goes home same day). Where the patient has carpal tunnel symptoms in both arms, only one side is operated on at a time. Following surgery, relief of carpal tunnel syndrome symptoms is often immediate. The bandages and sutures are removed 10 - 14 days after surgery and you should avoid heavy use of your hand for 4 - 6 weeks following surgery. No wrist splints should be worn following carpal tunnel surgery, as these are likely to be ineffective and harmful.

Other treatments such as nerve and tendon exercises, wrist splints, pyridoxine tablets, therapeutic ultrasound are of unknown benefit and have not been sufficiently studied to make any useful recommendations regarding their use. Lifestyle changes such as avoiding a high salt intake (which causes water retention) and avoiding smoking (which reduces blood flow) whilst generally good for individual health have no effect on carpal tunnel syndrome.

Treatments such as diuretic (fluid) and anti-inflammatory tablets are unlikely to be beneficial and have significant side effects.