Carpal Tunnel Syndrome (Wrist Nerve Compression)

Carpal Tunnel Syndrome Definition

Carpal tunnel syndrome is a condition where there is a tingling pain, numbness, and weakness of the thumb, index, and the middle fingers caused by irritation of the median nerve. It is a common condition in this day and age of excessive computer use and video gaming. The median nerve carries sensations from the thumb, index, and middle fingers of the hand. Along with some tendons, the median nerve passes through the carpal tunnel, which is located between wrist muscles and wrist bones. If there is a swelling or a change in position of the tissue inside the carpal tunnel, the median nerve is squeezed and irritated. This results in pain, numbness, and tingling.

Carpal Tunnel Syndrome Incidence

Carpal tunnel syndrome is very common condition, affecting 5 to 15% of the general population population. The incidence rises to as much as 50% in patients within the high risk group. More women are affected than men and the majority of carpal tunnel syndrome patients are in the 45 to 60 year age group. There is a distinct occupational hazard associated with carpal tunnel syndrome and therefore people engaged in jobs where there is forceful and repetitive movements are more likely to develop the condition.

Carpal Tunnel Syndrome Pathophysiology

The carpal tunnel is a small passageway through which nerves and muscle tendons pass between the forearm and the hand. It is formed by the wrist bones (carpal bones or carpus) and a connective sheath. The carpal tunnel is located on the palmar surface of the wrist and is narrow. The structure that pass through it are therefore in very close proximity. These include nine muscle tendons and one nerve – the median nerve.

Picture of the carpal tunnel anatomy from Wikimedia Commons

All nerves have a protective outer covering (myelin), which also helps in transmitting signals through the nerves. Any condition that can damage the nerve or result in demyelination (loss of myelin) can result in irregularities in carrying the signals. In carpal tunnel syndrome, there is a very high pressure inside the carpal tunnel as the tendons swell due to overuse. This compresses the median nerve resulting in sensations of pain, numbness, tingling, and weakness. Over time the median nerve may even be damaged to some extent.

Carpal Tunnel Syndrome Symptoms

Carpal tunnel syndrome starts as a vague ache in the wrist that spreads to the hand or forearm. People suffering from carpal tunnel syndrome present with the following symptoms.

Location

Thumb, index, middle and ring fingers are affected in carpal tunnel syndrome while the little finger is often unaffected. The dominant hand is more commonly affected but both hands may experience symptoms.

Sensation

Tingling or numbness in the fingers and hands are a major symptom. The abnormal sensations are often felt upon awakening or after activities like reading the newspaper, driving, and painting. The hands may also feel cold or hot all the time.

Pain

Pain radiating from the wrist to the arm or spreading down into the palm or fingers is characteristic of carpal tunnel syndrome. The pain tends to worsen after repetitive or forceful use of the hands.

Weakness

There is some degree of muscle weakness of the hands over time. A gradual loss of grip and increased tendency to drop things and objects may be noticed. This grip strength can be electronically measured and monitored over time.

Other

Stiffness of the joints in the hands is also commonly reported although the joints itself may not be diseased. There may also be a noticeable difference in skin color of the hand.

Carpal Tunnel Syndrome Causes

Carpal tunnel syndrome occurs due to increased pressure on the median nerve. However, there are various other mechanisms of injury that may affect the median nerve. Although other causes do not contribute to carpal tunnel syndrome itself, it does give rise to similar symptoms and should therefore be considered.

Anatomic factors like a smaller or bigger carpal tunnel, a wrist fracture, injury, or a dislocation can change the space within the tunnel. This may sometimes create more pressure on the median nerve even without swelling of the muscle tendons.
Some diseases like diabetes and alcoholism increase the risk of nerve damage.
Inflammation of the wrist tendons caused by rheumatoid arthritis or an infection can exert pressure on the median nerve even though there is no overuse of the hand.
Tumors near the median nerve can compress the nerve and result in pain and numbness.
Fluid retention in certain conditions (like with pregnancy, obesity, menopause, kidney failure, and thyroid disorders) can increase the pressure within the carpal tunnel. This irritates the median nerve.
Occupational factors that create pressure on the median nerve may damage the nerves and cause hand pain.
Other factors like lack of aerobic exercise, pregnancy, breastfeeding and use of devices like a wheelchair or walking aid may also cause carpal tunnel syndrome.

Carpal Tunnel Syndrome Risk Factors

Repeated and forceful movements of the hand are by far the greatest risk factor for developing carpal tunnel syndrome. Other risk factors that may contribute to carpal tunnel syndrome include :

Advancing age
Being female
Family history of carpal tunnel syndrome
Sudden increase in body mass index (BMI)
Shape of the wrist (a square shape)
Short height and smaller stature

Carpal Tunnel Syndrome Complications

Carpal tunnel syndrome is not fatal, but if it is left treated it can result in complete and irreversible damage of median nerve. This damage can cause a loss of hand function. With the dominant hand being most likely to be affected, these complications can leave the person permanently disabled and unable to work. This in turn can contribute to depression.

Carpal Tunnel Syndrome Diagnosis

The symptoms along with a medical history may raise the suspicion of carpal tunnel syndrome. The following features along with findings of diagnostic investigations may confirm the diagnosis.

Pattern and timings of symptoms help differentiate a carpal tunnel syndrome from other conditions. Unaffected little finger and waking up during the night or while holding a newspaper or a phone, are typical of carpal tunnel syndrome.
A physical or sensory examination tests the feeling in the fingers and the strength of the muscles in the hand. The test includes putting pressure on the median nerve at the wrist by bending the wrist or by pressing or tapping on the nerve. These actions can bring symptoms in many people. Tingling sensations due to tapping over the nerve or flexing the wrist are known as Hoffmann-Tinel or Phalen sign, respectively.
An x-ray of the affected wrist can exclude a fracture or arthritis.
An electromyogram can measure the tiny electrical signals produced in muscles at rest and during contraction. An irregular electromyogram may indicate muscle damage.
A nerve conduction study can reveal the presence of carpal tunnel syndrome. In a damaged median nerve, electrical impulses will be slow.
A wrist thickness-to-width ratio of more than 0.7 may be indicative of carpal tunnel syndrome.

Carpal Tunnel Syndrome Treatment

Treatment depends on the severity of the symptoms. Treatment options include simple lifestyle measures, use of a wrist splint, medications, and surgery.

Devices like a wrist splint help relieve symptoms of tingling and numbness experienced while sleeping.
Physical therapy consisting of an aerobic fitness program may regulate the BMI and provide relief in some patients.
Medications like non-steroidal anti-inflammatory drugs (NSAIDs) can bring temporary relief from pain from carpal tunnel syndrome.
Corticosteroids injections decrease inflammation and swelling. This relieves pressure on the median nerve and decreases pain.
Treating or managing underlying disease like rheumatoid arthritis and diabetes may decrease symptoms of carpal tunnel syndrome.
Pain relievers like aspirin, ibuprofen, or naproxen can ease the pain.

Carpal Tunnel Syndrome Surgery

Surgical procedures are reserved for severe or persistent cases. In carpal tunnel surgery, the ligament pressing on the nerve is cut. This relieves pressure on the median nerve and is therefore known as carpal tunnel release. Carpal tunnel surgery can be an open surgery or an endoscopic procedure.

In open surgery, a large cut is made in the palm of the hand over the carpal tunnel. The ligament is then cut to free the nerve.
In endoscopic surgery, an endoscope (a telescope-like device with a tiny camera) is used. A small cut is made in wrist to perform the surgery.

Carpal Tunnel Syndrome Lifestyle

Several simple lifestyle measures may help in providing temporary relief from the symptoms. Avoiding repetitive activities or taking breaks in between, rotating the wrists, stretching palms and fingers, wearing a wrist splint at night, and avoiding sleeping on the hands helps. It is possible for carpal tunnel syndrome to resolve with just lifestyle measures. However, it often requires a complete cessation of physical activities that tend to cause and exacerbate the condition.

Carpal Tunnel Syndrome Prevention

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Carpal tunnel syndrome is preventable to some degree. A person who is at greater risk of developing the condition, particularly when it is work related use of the hand, can undertake more ergonomic alternatives to complete the same tasks. Overall the key to prevention irrespective of the cause is to minimize stress on hands and wrists. Reducing unnecessary force and relaxing the grip helps. Frequent periods of rest during continuous activity is also helpful but tends to delay the onset of carpal tunnel syndrome in high risk patients, rather than prevent the condition altogether.

References :

http://emedicine.medscape.com/article/327330-overview

http://www.ninds.nih.gov/disorders/carpal_tunnel/detail_carpal_tunnel.htm

http://www.assh.org/PUBLIC/HANDCONDITIONS/Pages/CarpalTunnelSyndrome.aspx