Carpal Tunnel Syndrome
What is meant by carpal tunnel syndrome?
Carpal tunnel syndrome describes a condition of chronic pressure on the median nerve (nervus medianus) in the so-called carpal tunnel (a canal in the wrist formed by the wrist bones and ligaments).
Initially, the affected person will notice a tingling sensation in one or more of the fingers supplied by the median nerve (thumb, index finger, middle finger and the thumb side of the ring finger). Often, the patient awakes during the night due to pain which can stretch as far as the arm and shoulder. Tingling sensations and numbness may also be present in the affected finger. Pain can often be reduced by shaking the hand. The fingers are often stiff and may even show swelling in the morning.
In later stages, permanent motor disturbances appear in the fingers. For example, the affected individual may no longer be able to hold a needle or he may experience difficulties when trying to button his shirt.
If pressure on the nerve has existed over a long period of time, pain may vanish, but in many cases the fingers are then left completely numb. The thenar muscles atrophy because they are no longer receiving any impulses from the nerve. At this stage, the nerve is functionally dead and can no longer regenerate.
What causes carpal tunnel syndrome?
This condition is caused by a narrowing of the space needed for gliding of the median nerve and flexor tendons, e.g. following bone fractures or through swelling of scar tissue.
Additionally, the contents of the gliding space may increase, e.g. through tendosynovitis, rheumatic illnesses, ganglions, tissue swelling during pregnancy, during menopause or following increased stress on the wrist.
Even anatomical anomalies such as atypical muscle paths can lead to carpal tunnel syndrome. In many cases, no specific cause can be identified.
How is carpal tunnel syndrome diagnosed?
The doctor's diagnosis is made based on the individual's clinical history and a clinical examination. The feeling in the fingers and the condition of the thenar muscles is checked. This is followed by a neurological examination (electroneurography) which tests the speed at which a stimulus is conducted by the median nerve. If a slowing of the measured nerve conduction speed is detected in the wrist area, damage due to pressure on the nerve must be assumed.
Other clinical disorders having similar symptoms but other causes have to be ruled out. For example, the median nerve may be under pressure at another point, e.g. at the elbow (proximal median compression, Pronator teres syndrome) or in the area of the neck and shoulder (cervical spine syndrome, scalenus anterior syndrome, thoracic outlet syndrome, cervical rib).
How can carpal tunnel syndrome be treated?
If left untreated, the nerve gradually dies due to the continuous pressure in the carpal canal, and it will no longer be able to recover. The numbness in the affected finger becomes permanent.
In mild cases or in the early phases of carpal tunnel syndrome, anti-inflammatory drugs and Vitamin B6 preparations can lead to an improvement in the symptoms. A special brace worn at night keeps the wrist immobilized.
Cortisone injection into the carpal canal is not risk-free and should no longer be carried out.
If conservative treatments are unsuccessful, or if symptoms reoccur, surgery is the best option.
How is the operation performed?
Through a small incision in the hand area, the transverse carpal ligament is divided. In this way, the nerve is relieved of pressure. Should any chronically swollen paratenon be found near the nerve, it may also be removed. Plexus anaesthesia (anaesthesia of the arm only) or general anaesthesia can be used for the operation; in rare cases, a local anaesthetic may be used. As a rule, pain disappears immediately after the operation, while the sensory disturbances in the finger often improve within a few weeks. The process depends upon the severity of the nerve damage. Only under particular conditions – where there is no atrophy in the plenar muscles, no limitation of movement in the wrist, no scar tissue from previous wrist injuries, no severe tendosynovitis – can the operation be performed by endoscope.
Following the operation, the wrist is immobilized for a period of days. However, a program of finger exercises should be begun immediately.
Must I stay in the hospital?
The procedure is generally carried out on an outpatient basis. A general anaesthetic or partial anaesthesia of the arm is used depending on the preference and condition of the patient. In cases of serious accompanying illnesses, such as coronary heart disease, severe vascular disorders, severe diabetes mellitus, kidney insufficiency, bronchial asthma and others, an in-patient hospital stay may be necessary.
Which complications can occur from the operation?
As with every operation, carpal tunnel release surgery can also result in complications such as post-operative bleeding, swelling, haematoma or infection of the wound. Generally, these complications can be easily controlled.
Rare, serious complications such as the onset of reflex sympathetic dystrophy require prompt in-patient after-care.
In cases where the nerve damage is too far advanced, it may not be possible to restore feeling in the fingers completely.