Carpal tunnel syndrome, also called carpal tunnel syndrome, is a disease caused by compression of the median nerve, responsible for the innervation of the external region of the hand. In this text we will explain which anatomical structure is the carpal tunnel, how does the median nerve compression appear and what are the symptoms and treatments for this disease.
To facilitate the understanding of the text, follow the explanations with the illustrations provided.
Carpus is a Greek word for fist. The carpal tunnel is a kind of tunnel or canal in the region of the wrist with the approximate diameter of a thumb. Its floor is the bones of the handle and its ceiling is the transverse carpal ligament. Inside the carpal tunnel pass the 9 tendons responsible for the movements of the fingers and the median nerve, responsible for the innervation of the outside of the hands, as shown in the image below.
Any change that causes a decrease in space within the carpal tunnel may lead to compression of the median nerve causing the typical symptoms of carpal tunnel syndrome. Most of the time this compression of the median nerve occurs by inflammation and swelling of the structures inside the carpal tunnel, such as the tendons. Accumulation of substances like proteins or blood also causes increased pressure inside the tunnel.
Carpal tunnel syndrome is a fairly common condition, affecting about 1 to 5% of the population. The disease is more common in women, especially in obese women.
We know several risk factors for the syndrome, but in many cases we can not identify the exact cause. We know that jobs that require repetitive movements, which induce prolonged push-ups and/or extensions, or that place pressure on hands and wrists, increase the risk of tendon swelling, favoring medial nerve clamping.
Contrary to popular belief, working with a computer for several hours does not seem to be associated with an increased risk of developing carpal tunnel syndrome. Work so far has shown that the risk to computer users for up to 7 hours a day is not greater than that of the general population.
In addition to the mechanical inflammation caused by repeated wrist movements, a number of diseases and conditions can increase the risk of carpal tunnel syndrome, even in people who do not perform work requiring constant movements of the arms, hands or wrists. These include:
Because carpal tunnel syndrome is caused by compression and suffering of the median nerve, its classic symptoms are pain and paresthesia (tingling and loss of sensation) located in the region of the hand innervated by this nerve (see illustration at the beginning of the text).
The symptoms are usually worse at night and often wake the patient. The pain can be aggravated by the extension or flexion of the wrists. Activities such as driving vehicles, reading, typing or holding the phone may be enough to trigger the pain.
In up to 65% of cases, carpal tunnel syndrome affects the wrists bilaterally, but the most common is that one of the wrists is more symptomatic than the other.
If left untreated, the condition usually worsens over time, leading to motor changes such as weakness to move the fingers. The patient may become unable to hold objects.
The diagnosis is usually clinical and can be proved by electroneuromyography, an examination used to evaluate nerve conduction and the response of muscles to it.
Two simple physical tests aid in diagnosis by triggering the typical pain of carpal tunnel syndrome:
a) The Phalen maneuver consists of the maximum flexion of the fists performed with the back of the hands leaning against one another as in the photo above.
b) The Tinel test consists of percussion of the median nerve in the carpal tunnel region.
In mild cases the wrist rest associated with immobilization with local splint and ice may be sufficient to reduce edema and relieve symptoms. Anti-inflammatories can be used to alleviate the pain although its use in this disease is controversial, since there are doubts about its effectiveness.
Injection of corticosteroids at the site is a good option in moderate cases.
If there are identifiable causes like rheumatoid arthritis or hypothyroidism, treatment of these diseases helps improve compression in the tunnel.
Surgery for carpal tunnel syndrome is indicated in moderate/severe cases that do not improve with clinical treatment. The procedure aims at tunnel decompression and release of the median nerve through a cut of the transverse carpal ligament, which can be done endoscopically or through traditional surgery.
