What is Carpal Tunnel Syndrome?
Carpal tunnel syndrome (CTS) is a condition brought on by increased pressure on the median nerve in an osteofibrous tunnel located at the level of the heel of the hand, the carpal tunnel.
The median nerve controls the sensitivity of the thumb, index finger, middle finger and the external part of the ring finger. It controls the workings of small muscles located in the hand and base of the thumb.
1 – Ulnar nerve
2 – Radial nerve
3 – Sensitive territory in the median nerve
The nerve enters the hand via a tunnel located in the wrist. This tunnel consists of a gutter closed in front by a very thick ligament. Long flexor finger tendons surrounded by a thin membrane, called synovium, also go through this channel.
Carpal tunnel syndrome happens when pressure builds up from swelling in this tunnel and puts pressure on the nerve. When the pressure from the swelling becomes great enough to disturb the way the nerve works, numbness, tingling, and pain may be felt in the hand and fingers.
Usually, the cause is unknown. Pressure on the nerve can happen in several ways: swelling of the lining of the flexor tendons called tenosynovitis; joint dislocations, fractures, and arthritis can narrow the tunnel; keeping the wrist bent for long periods of time. Fluid retention during pregnancy can cause swelling in the tunnel and symptoms of carpal tunnel syndrome, which often go away after delivery. Thyroid conditions, rheumatoid arthritis, and diabetes can also be associated with carpal tunnel syndrome. There may be a combination of causes.
Carpal tunnel syndrome symptoms usually include pain, numbness, tingling, or a combination of the three.
The numbness or tingling most often takes place in the thumb, index, middle finger, and ring finger.
The symptoms are usually felt during the night but may also be noticed during daily activities such as driving or reading a newspaper. Patients may sometimes notice a weaker grip, occasional clumsiness, and a tendency to drop things. In severe cases, sensation may be permanently lost and the muscles at the base of the thumb slowly shrink (thenar atrophy), causing difficulty to pinch.
Diagnosis of carpal tunnel syndrome
A detailed history including medical conditions, how the hands have been used, and whether there were any prior injuries is important. An x-ray may be used to check for the other causes of the complaints such as arthritis or a fracture. In some cases, laboratory tests may be done if there is a suspected medical condition that is associated with CTS. Electrodiagnostic studies (NCV–nerve conduction velocities and EMG–electromyogram) may be done to confirm the diagnosis of carpal tunnel syndrome as well as to check for other possible nerve problems.
Treatment of carpal tunnel syndrome
- Medical treatment
Symptoms may often be relieved without surgery. Identifying and treating medical conditions, changing the patterns of hand use, or keeping the wrist splinted in a straight position may help reduce pressure on the nerve. Wearing wrist splints at night may relieve the symptoms that interfere with sleep. A steroid injection into the carpal tunnel may help relieve the symptoms by reducing swelling around the nerve.
- Surgical treatment
When symptoms are severe or do not improve, surgery may be needed to make more room for the nerve. Pressure on the nerve is decreased by cutting the ligament that forms the roof (top) of the tunnel on the palm side of the hand (see Figure 3). Incisions for this surgery may vary, but the goal is the same: to enlarge the tunnel and decrease pressure on the nerve.
Following surgery, soreness around the incision may last for several weeks or months. The numbness and tingling may disappear quickly or slowly. It may take several months for strength in the hand and wrist to return to normal. Carpal tunnel symptoms may not completely go away after surgery, especially in severe cases.
No surgical intervention guarantees that there will not be secondary complications. Any decision to intervene must be made aware of these risks, which the surgeon must have informed you about.
Common complications related to hand surgery
- Nosocomial infections: they are rare and easily controlled with early diagnosis. Antibiotics and a new intervention may be necessary
- Hematoma: the diagnosis must be early and surgical revision may also be necessary
- Sudeck syndrome (algodystrophy): this is a “disruptive” pain when there is no underlying problem. Its manifestation is independent of the type of surgery and can occur even after a simple immobilization. The hand becomes swollen, painful, and gradually stiffens. The evolution can be very long. Sequelae are possible (residual pain, stiffness of the fingers and/or wrist, sometimes of the shoulder). Treatment is difficult and uses specific rehabilitation techniques
- Anaesthesia accident: the easiest but the most serious, including death (1 death per 100,000 to 150,000 anaesthesia).
Complications specific to the carpal tunnel syndrome
- Persistence of sensory disorders. Three diagnoses are possible and will be discussed with the surgeon with the help of a new electromyogram, if necessary:
- Incomplete opening of the carpal tunnel, requiring another surgical intervention.
- Associated neurological lesion (most common event): it is a nerve compression at another level (elbow, cervical spine …) or nerve damage itself (polyneuritis, diabetic neuropathy).
- Median nerve wounds (rare). Intervention must be relatively quick in order to fix the nerve.
- Fingers jump or synovitis stenosing: it is more the continuation of the causal disease than a carpal tunnel complication. Appropriate treatment should be undertaken: rest, infiltration and possibly surgery.
- Recurrence: even if it is rare, it is always sought in case tingling comes back. An electromyogram will be requested. A reoperation can be suggested.
© 2011 American Society for Surgery of the Hand. Developed by the ASSH Public Education Committee.