Carpal tunnel syndrome

Carpal tunnel syndrome is defined by compression of the median nerve, which passes through the carpal tunnel, a narrow passage at the base of the hand. The floor of the tunnel is formed by the carpal bones, and the roof of the tunnel is formed by a thick ligament called the anterior annular ligament. This means that the space in the carpal tunnel cannot change. The median nerve passes through the tunnel, accompanied by 9 tendons (finger and thumb flexors). Most often, compression of the median nerve is due to inflammation of these tendons (called synovitis), which take up more space in the tunnel, thus compressing the nerve. There are many causes of inflammation. When this nerve is compressed, it can cause unpleasant symptoms such as pain, tingling and loss of sensitivity in the fingers.

The median nerve is indispensable, as it controls sensation in the thumb, index finger, middle finger and half of the ring finger. It also enables movement of certain muscles at the base of the thumb (thenar). If treatment is not undertaken in time, and the nerve remains compressed for a prolonged period, it gradually loses its function (sensory and motor), sometimes permanently.

Carpal tunnel surgery opens the carpal tunnel, relieving pressure on the nerve and painful tingling. This allows the nerve to regenerate and resume its function (nerve regrowth is slow, at 1 mm per day). In the event of prolonged and severe damage, motor and sensory recovery may be impossible, or only partially possible.

Carpal tunnel syndrome is very common, especially among women in their fifties or during pregnancy, as well as heavy-duty workers and housekeepers, who put prolonged and intense strain on their hands. Both hands are frequently affected.

The exact causes of the syndrome can vary from one individual to another. They often include genetic factors, underlying diseases such as diabetes or hypothyroidism, or trauma to the wrist. In some cases, the injury may be linked to work or leisure habits involving repetitive hand movements, leading to inflammation of the surrounding tendons and increased pressure on the median nerve. In most cases, there is no specific cause.

Symptoms of carpal tunnel syndrome usually manifest as tingling or numbness, often felt in the fingers, particularly the thumb, index and middle fingers. These symptoms are often more pronounced at night or upon awakening, leading to pain that can extend to the elbow or even the shoulder.
You should consult your doctor if you experience :

• Tingling or numbness in the hand
• Especially in the thumb, index and middle fingers
• Mainly at night or when waking up in the morning
• Sometimes associated with pain that may go up to the elbow or shoulder
• Loss of sensitivity in fingertips or involuntary dropping of objects

As the disease progresses, finger sensitivity may diminish. In advanced stages, tingling is permanent during the day, strength diminishes and may be associated with dropping objects.

Your family doctor may prescribe a neurological examination to confirm nerve compression at the carpal tunnel and its severity, as well as to rule out other possible sites of compression (e.g. cervical). An electromyogram (ENMG) measures nerve conduction velocities. This test helps to assess the severity of the injury and guide the choice of treatment, particularly with a view to possible carpal tunnel surgery.

Treatment depends on the severity of symptoms and the extent of nerve damage on neurological examination:

• A resting splint may be sufficient in early cases
• in persistent cases, cortisone infiltration may relieve symptoms
• In severe or long-standing cases, carpal tunnel surgery is required to release the nerve by opening the carpal anterior annular ligament. The procedure is performed in the Leman Hand Clinic’s operating theatre, under local anaesthetic, via a mini-incision of around 2 cm.

Useful links:

• The British Society for Surgery of the Hand