What is Carpal Tunnel Syndrome?
Carpal tunnel syndrome is one of the most common conditions affecting the hands. It occurs when one of the nerves to the hand (the median nerve) becomes compressed as it passes into the hand through the carpal tunnel. The carpal tunnel is formed by the small bones of the wrist, which are arranged in an arch shape and a strong ligament called the transverse carpal ligament. The median nerve passes through the carpal tunnel along with nine tendons that are used to flex the fingers and thumb.
Causes of Carpal Tunnel Syndrome
The median nerve can be compressed within the carpal tunnel by thickening of the overlying transverse carpal ligament, bony spurs arising from the carpal bones or most commonly from swelling of the accompanying tendons or their lining within the tunnel.
Tendon inflammation and swelling can be the result of injury or overuse, a systemic inflammatory condition (eg. rheumatoid arthritis) and a variety of medical conditions (pregnancy, thyroid disorders). All of these, in turn, have been implicated in the development of carpal tunnel syndrome.
Symptoms of Carpal Tunnel Syndrome
In the hand, the median nerve is responsible for sensation (feeling) of the thumb, index finger, middle finger and half of the ring finger. It also controls the group of small muscles at the base of the thumb. This is why the symptoms of carpal tunnel syndrome are classically a change in sensation (pins and needles or numbness) over the thumb, index, middle and ring fingers as well as weakness of various movements especially involving the thumb.
Symptoms are often worse at overnight (commonly waking patients from sleep) or by activities that put increased pressure on the carpal tunnel such as driving for long periods of time. It is not uncommon for certain workplace activities to exacerbate the symptoms of carpal tunnel syndrome, whether or not a job has ‘caused’ the underlying carpal tunnel syndrome, however, is often a very difficult question to answer.
Diagnosis of Carpal Tunnel Syndrome
Assessment of patients with suspected carpal tunnel syndrome will always begin with a thorough history – and often the diagnosis is clear at this point. It is very important, however, to confirm this diagnosis with a targeted examination to exclude some other conditions that can mimic this common condition.
In certain cases, a series of tests known as nerve conduction studies will be ordered to specifically assess and compare the function of the median nerve. Whilst not a particularly pleasant investigation, this can be very important to ensure that you do not undergo an unnecessary or even incorrect procedure.
Surgery for Carpal Tunnel Syndrome
The concept of surgery for carpal tunnel syndrome is very straightforward – divide the thick transverse carpal ligament to ‘open up’ the carpal tunnel therefore taking pressure off the median nerve.
The results of carpal tunnel release surgery are dependant on a number of factors, the most important being the severity of the nerve dysfunction prior to surgery. In cases of severe or particularly prolonged compression, there can be irreversible changes in the nerve fibres and also the target muscles such that even after the compression has been relieved, nerve function does not return to normal.
In mild and moderate cases, return to normal function is the expected result following surgery even though this sometimes takes months in certain patients. In the more severe cases, recovery of normal function cannot be guaranteed but it is still critically important to decompress the nerve to prevent further irreversible deterioration.
Timely referral and assessment by a hand surgeon will allow your condition to be thoroughly assessed and all of your options presented and considered.
Surgical Techniques for Carpal Tunnel Syndrome
In general there are two techniques for performing carpal tunnel release. The traditional technique is an open carpal tunnel release where the transverse carpal ligament is divided through an approximately 3cm incision on the palmar surface of the hand. More recently a minimally invasive (keyhole) technique has been developed where a small camera is inserted into the carpal tunnel through an incision less than 1cm in the skin, the transverse carpal ligament is then divided from underneath leaving the overlying skin intact.
Both techniques are very effective and reliable for treating carpal tunnel syndrome. The keyhole (endoscopic) technique has been shown to be associated with an earlier average return to work compared to open surgery but there are certain cases where this technique may not be appropriate.
Non-operative Treatment of Carpal Tunnel Syndrome
In early and mild cases, certain non-operative measures have been shown to significantly reduce symptoms and improve hand function. Referral to an experienced hand therapist can be very useful in this regard. If these measures are no longer effective or if your case is already quite severe, surgery to perform a carpal tunnel release is the definitive treatment option.