• Definition: Nerve compression syndrome of the median nerve at wrist level in the carpal tunnel. It is the most common nerve compression syndrome in humans.
  Overview: The carpal tunnel is an anatomical area bounded dorsally by the carpal bones (carpus) and palmarly by a transverse ligament (flexor retinaculum). The structures bounding the carpal tunnel are inelastic. The median nerve and the flexor tendons of the fingers and thumb pass through the carpal tunnel. Any increase in volume in the carpal tunnel – wrist fracture, ganglion, rheumatic disease with inflammation of the flexor tendon sheaths, gout or hormone fluctuations (e.g. with pregnancy, menopause, hypothyroidism) – thus increases the pressure. Prolonged exposure to repeated bending and working with vibrating tools can also cause carpal tunnel syndrome.
• Symptoms: The constriction of the median nerve can cause paraesthesia or, in the case of prolonged pressure, reduced sensation in the thumb, index finger, middle finger and the side of the ring finger adjacent to the middle finger, as well as a loss of thumb strength. The symptoms are often more severe at night than during the day. Such patients often shake their hands back and forth to reduce the tingling sensation. The pain sometimes radiates into the forearm.
• Diagnosis: Apart from the often typical medical history check and clinical examination, patients receive a neurological examination, to measure nerve conduction velocity (ENMG), and a sonography. Your physician can use a laboratory test to find out the possible causes (e.g. change in blood sugar levels and thyroid gland dysfunction).
• Differential diagnoses: Polyneuropathy, nerve compression in another region (e.g: pronator compartment syndrome and nerve root compression due to cervical osteoarthritis).
• Therapy: Mild nerve compression syndrome can be treated at night using a wrist splint to keep the wrist in a neutral position. The diameter of the carpal tunnel in hyperextension and flexion is smaller. The splint helps prevent this position-dependent constriction. If nerve compression is pronounced or conservative therapy fails, the mechanical cause is treated surgically, e.g. under local anaesthesia and ischemia. Surgical severing of the transverse carpal ligament (flexor retaniculum) relieves the pressure on the median nerves. This can be done endoscopically through an incision at the wrist crease or through open surgery with an incision at the level of the palm. The two procedures yield equivalent long-term results. Since the incision is made outside of the hand’s strain zone during endoscopic surgery, rehabilitation after splitting the roof of the carpal tunnel endoscopically is somewhat faster, making it suitable for people with physically demanding professions.
• Post-operative care: You can safely go ahead and move your hand freely. Depending on the type of work, you can carry out physically demanding work with your hand again in from four to six weeks. Depending on the progression, ergotherapeutic post-operative care can improve scarring and thus the results of the operation.
• Prognosis: The prognosis depends on the existing pressure damage to the nerve. The paraesthesia usually improves rather quickly. It takes months or years for strength and normal sensation to return. Any post-operative haematoma, pain at the base of the thumb or a painful scar often gets better over time (sometimes taking several weeks) or can be treated with occupational therapy. Chronic pain syndrome (CRPS), incomplete splitting of the carpal roof, surgically induced nerve damage or recurrence are rare. It is a standard surgical procedure with good post-operative results.