What causes carpal tunnel syndrome?

Several causes can be at the root of the problem, including repeated bending movements, hormonal imbalances, a structural or bone anomaly, or certain chronic illnesses.

Diabetes, smoking, pregnancy, osteoarthritis, hyperthyroidism, excess weight, menopause and radius fracture are among the most common risk factors.

What are the symptoms?

The main symptoms of carpal tunnel syndrome, in order of appearance, are:

• Pain or burning sensation in the hand, fingers or forearm. 
• Numbness and tingling in the hand, especially in the thumb, index and middle fingers.
• Symptoms get worse at night.  Night awakenings. Need to shake hands.
• Worsening of symptoms with manual activity or driving.
• Swollen feeling in the fingers and hand.
• Weakness, clumsiness and loss of dexterity.

Numbness and tingling in the palm of the hand or in the fingers are usually the first signs of the disorder. These symptoms occur especially at night, or early in the morning, and often cause insomnia or nocturnal awakenings. Itching or burning pain is sometimes felt. Patients often have to shake the affected hand to remove numbness.

During the day, symptoms can be triggered by activities such as driving, prolonged phone use, or reading the newspaper.

With time and the progression of the problem, there is a loss of sensitivity, at first transient and then permanent, in the fingers of the hand. Affected patients lose touch and the sensation of touch, in the thumb, forefinger, middle finger and half of the fourth finger. Subsequently, when the condition becomes more severe, atrophy can be observed, which is a weakening of the muscles from the base of the thumb to the palm of the hand. A loss of manual dexterity and a decrease in the strength of the thumb-index pinch follows. It becomes difficult to manipulate small items such as coins or buttoning clothes. Clumsiness appears to the point of dropping pens and having trouble writing.

How to diagnose it?

The diagnosis is based mainly on clinical examination and symptom description. Various challenge tests, including the Tinel sign, Durkan compression test, limb elevation test and Phalen manoeuvre, can also be used to assess symptoms and measure the severity of the syndrome. The Scratch Collapse Test is very useful for confirming nerve damage. Electromyography (EMG) and nerve conduction tests are complementary tests sometimes recommended to provide differential diagnosis and to measure the severity of nerve damage. They also make it possible to accurately confirm the site of nerve compression.

All patients presenting with hand numbness in the area corresponding to the median nerve (major index thumb) should be examined not only for carpal tunnel syndrome, but also for compression of this nerve in the elbow, under the lacertus fibrosus. The scratch collapse test is a very little known but very useful physical examination manoeuvre for the diagnosis of nerve compression such as CTS or lacertus fibrosus syndrome.

Indeed, between 33 and 50% of patients with median nerve compression in the carpal tunnel also have a similar compression even higher, at the elbow and forearm. If this compression is not identified and treated, many symptoms may persist after carpal tunnel surgery. Ignorance of this pathology is a common cause of the failure of carpal tunnel surgery.

Non-surgical treatment

Beyond maintaining a healthy lifestyle and controlling chronic diseases, several measures can help to relieve symptoms.  Conservative management includes stretching and nerve movement exercises, night splinting, prevention of incorrect or non-ergonomic postures, and reduction or elimination of repetitive movements.

Wearing a night orthosis can be recommended for four to six weeks. If, at the end of this period, symptoms are still present or if signs reappear when the orthosis is abandoned, surgery is required. Orthotics are not a permanent solution to the problem and can, on the contrary, adversely affect the treatment protocol. 

Cortisone injections, preferably performed under ultrasound monitory, are sometimes performed for the purpose of temporarily relieving the pressure inside the carpal tunnel. They can also be used as therapeutic tests when the diagnosis is uncertain. These injections may mask the symptoms of compression. They should not be repeated to avoid the development of irreversible neurological damage.