What is carpal tunnel syndrome?|
The carpal tunnel is a tunnel of bones and ligaments at the wrist. It allows the passage of 9 tendons and a major nerve (the median nerve) to the wrist. Carpal tunnel syndrome is the disorder where the median nerve is compressed as it passes through the carpal tunnel. This causes an interruption in the flow of nerve information about sensation and movement in the hand.
What causes the carpal tunnel syndrome?
Any factor that either increases the contents of the carpal tunnel, or conversely decreases the space available in the tunnel can lead to the carpal tunnel syndrome. These events lead to an increase in the pressure in the carpal tunnel so that the median nerve is squashed. These factors can be divided into the following subgroups:
- Mechanical - for example repetitive wrist movement, vibration,
fractures of the wrist.
- Structural - abnormal muscles, tendons or blood vessels. Cysts in
- Infectious - infection of the wrist joint.
- Inflammatory rheumatoid arthritis, gout.
- Tumours/growths fat or fibrous tumours. Bony outgrowths.
- Hormonal pregnancy and menopause.
- Blood related bleeding in the tunnel, or blood vessel aneurysm
- Other diseases diabetes, thyroid disease.
The following symptoms are commonly reported:
- Numbness or tingling in the area of the hand supplied by the median nerve (thumb + the first 2 ½ fingers, and the corresponding area of the palm).
- Pain in the hand in the median nerve area, which may radiate up the arm to the shoulder or neck.
- Weakness or clumsiness of the hand, especially the thumb.
- Wasting of muscles in the hand, especially the muscles around the thumb.
- Loss of sensation in the median nerve area of the hand.
- Dryness of the skin in the hand.
Carpal tunnel syndrome progresses through a number of stages. Firstly numbness will occur without any nerve conduction problems. Next, the passage of nerve information is impaired. Lastly in the more severe cases of carpal tunnel syndrome there will be evidence of weakness and muscle wasting in the hand.
Patients report that the characteristic symptoms are worse at night, patients often wake with the pain. The symptoms are also worse if the wrist is bent. Symptoms are improved if the wrist is in the neutral position.
The dominant hand is most frequently affected, but the symptoms occur in both hands in 50% of sufferers.
It is estimated that between 1.5 and 5% of people are affected by the carpal tunnel syndrome. Carpal tunnel syndrome is twice as common in females than it is in males and it is more common in persons over the age of 55 years. Some studies have shown that there is a higher occurrence in some particular occupations such as assembly work, packing, clerical work, garment production, construction (manual work).
It is twice as common in overweight people. Carpal tunnel syndrome contributes significantly to time of work and ACC claims.
There are several different approaches to diagnosis:
- Provocative tests - here the doctor tries to bring out the symptoms by performing certain maneuvers. For example bending the wrist, compressing or tapping the wrist.
- Electrodiagnosis - this involves performing nerve conduction studies – the time taken for signals.To travel through the nerve. Signals take longer to travel through the median nerve when it is compressed within the carpal tunnel.
- Imaging - ultrasound scans, MRI scans, X-rays.
- Other signs - include wasting of muscles and loss of sensation in the median nerve area of the hand.
The first and most important step is to treat the underlying d