CARPEL TUNNEL SYNDROME*
Carpel tunnel syndrome occurs when the median nerve, which runs from the forearm into the palm of the hand, becomes pressed on or squeezed at the wrist. It is also referred to as median nerve entrapment neuropathy. The compression of the nerve occurs at the wrist as it travels through the carpel tunnel.
The Carpel Tunnel
The carpel tunnel is the passageway on the palmar side of the wrist that connects the forearm to the middle compartment of the deep plane of the palm. The tunnel consists of bone and connective tissue. Several tendons and nerves pass through it, in particular the median nerve. The canal is narrow and when any of the nine long flexor tendons passing through it swells or degenerates, the narrowing of the canal often results in the median nerve becoming compressed or entrapped.
The Median Nerve
The median nerve is one of the five main nerves arising from the brachial plexus (a complex of nerves in the neck). It continues down the arm to enter the forearm with the brachial artery. The median nerve is the main nerve that passes through the carpel tunnel. It innervates most of the flexor muscles in the forearm (the rest being supplied by the ulnar nerve). In the hand, the median nerve supplies motor innervation to the muscles on the thumb side of the hand and supplies sensory innervation mainly to the thumb, index and middle fingers and the radial half of the ring finger and adjacent palm.
Causes of Carpel Tunnel Syndrome (CTS)
CTS usually occurs only in adults, and it is more common in the dominant hand.
Most cases of CTS are of unknown cause, or idiopathic.
CTS is often the result of a combination of factors that increase the pressure on the median nerve and tendons in the carpel tunnel, rather than a problem with the nerve itself. Some of these factors include:
- Congenital predisposition. The carpel tunnel is simply smaller in some people than in others.
- Gender. Women are three times more likely to develop CTS, perhaps because the carpel tunnel is smaller in women than in men.
- Conditions that cause pressure on the median nerve at the wrist: obesity, oral contraceptives, hypothyroidism, arthritis including rheumatoid arthritis, diabetes.
- Trauma or injury to the wrist that causes swelling, such as sprain or fracture, especially Colles' fracture.
- Occupation. The international debate regarding the relationship between CTS and repetitive motion in work is ongoing. Occupational risk factors of repetitive tasks, force, posture and vibration have been cited. At most, it would appear that these may contribute to the development of CTS.
- Fluid retention during pregnancy or menopause.
- The development of a cyst (ganglion) or tumour in the tunnel.
- Acromegaly, which results from excessive growth hormone. Among other symptoms, this can cause the soft tissues and bones around the carpel tunnel to grow and compress the median nerve.
Symptoms and Signs of CTS
The main symptom of CTS is intermittent numbness in the area of the cutaneous innervation of the median nerve, namely the thumb, index and middle fingers and the radial half of the ring finger. Apart from numbness, there may be tingling ('pins and needles') or burning sensations and pain.
The symptoms usually start gradually, and often first appear in one or both hands during the night (probably because many people sleep with flexed wrists). A person with CTS may wake up feeling the need to "shake out" the hand or wrist. There may be the feeling that the fingers are useless and swollen, even though little or no swelling is apparent.
As the condition worsens, the numbness and tingling may be present during the day.
Pain in the wrists or hands may occur and can even radiate up the forearm. Decreased grip strength can also occur, making it difficult to form a fist, grasp small objects, or perform manual tasks. There may be a tendency to drop things.
In chronic and/or untreated cases, the muscles at the base of the thumb may waste away (atrophy). There may also be an inability to differentiate between hot and cold.
Diagnosis of CTS
Early diagnosis and treatment are important in order to avoid permanent damage to the median nerve.
The diagnosis is generally made from a combination of:
- Described symptoms.
- Clinical findings. The wrist is examined for tenderness, swelling and warmth. Each finger is tested for sensation, and the muscles at the base of the hand, the thenar eminence, tested for strength and signs of atrophy (wasting).
- Routine laboratory test and X-rays. These can reveal such conditions as diabetes, arthritis and fractures.
- Tinel's test. Tapping on, or pressing on, the front of the wrist may cause tingling or pain in the hand if CTS is present.
- Phalen's test. This a wrist-flexion test. It involves holding the forearms upright by pointing the fingers down and pressing the backs of the hands together. The presence of CTS is suggested if one or more symptoms, such as tingling or increased numbness, is felt in the fingers within one minute.
- A nerve conduction test. This is the definitive test used to diagnose CTS. This test measures how fast electrical impulses travel through the median nerve. If the impulse is slow or weaker than normal, it suggests that the nerve is being obstructed in the carpel tunnel.
- Ultrasound imaging. This can show impaired movement of the median nerve.
Treatment of CTS
Treatment for carpel tunnel syndrome should begin as early as possible. Underlying causes such as diabetes or arthritis should be treated first.
Generally accepted treatments include drugs, splinting and surgical release of the transverse carpal ligament.
- Diuretics, by removing water from the body, can decrease swelling and so reduce symptoms.
- Steroids, either orally or injected locally, will relieve pressure on the median nerve and provide immediate, temporary relief in persons with mild or intermittent symptoms. Steroids are not appropriate for extended periods.
- Vitamin B6 (pyridoxine) supplement may also ease the symptoms of CTS.
- Non-steroidal anti-inflammatory drugs can also be tried as an initial therapy.
The importance of wrist braces and splints in CTS is well known, but many people are unwilling to use them. They are definitely beneficial and recommended in mild to moderate cases. It is suggested that, for best results, the braces or splints should be worn at night and, if possible, during the activity primarily causing stress on the wrists.
This is generally recommended when symptoms persist unrelieved for six months, and especially if there is muscle weakness or atrophy. The surgery involves severing the band of tissue around the wrist to reduce pressure on the median nerve. Release of the transversal carpal ligament is known as "carpal tunnel release" surgery. This surgery is generally done under local anaesthesia, and is successful in some 95% of cases. Although symptoms may be relieved immediately after surgery (generally this is so), full recovery can take months.
- Hand exercises
Some hand exercises, including stretching exercises, may be helpful in the management of CTS, although there is some evidence that suggests they offer little if any benefit. These should be supervised by a physical therapist, since the wrong exercises, or exercises done improperly, may worsen the condition.
Carpel tunnel syndrome is a common condition that occurs in 2.7% of the general population. The average age of people with CTS is 40-50 years.
It is straight forward to diagnose, and the outcome with appropriate treatment is generally excellent.
*Copyright 2013: The Huntly Centre.
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