What is carpal tunnel syndrome? Definition
Carpal tunnel syndrome (CTS) is a painful and progressive condition of the wrist, hands, and fingers caused by the compression of the median nerve as it travels through the passage called the carpal tunnel. The tunnel lies in front of the wrist just over the carpal bones.
The main symptom of carpal tunnel syndrome is numbness of the fingers. It also causes weakness of the affected hand and loss of strength and hand function.
Most cases of mild CTS improve with treatment, especially when treated early. If not treated, the condition worsens with time and the sheath over the nerve can wear away leading to permanent nerve damage and loss of function of the hand.
There are several causes and risk factors that are responsible for this condition.
Knowing the anatomy of the wrist will make it easier to understand these various causes and other features of carpal tunnel syndrome.
Anatomy of the wrist
First, let us understand the anatomy of the wrist, as that is where changes that cause carpal tunnel syndrome take place.
The bony structure of the wrist consists of eight small bones called the carpal bones. They attach to each other by joints to facilitate the various movements of the wrist.
On the palm side, running across the width of the wrist is a strong band of tissue, which forms a tendon. This is attached on either side to the carpal bones.
So, we have a tunnel formed by the carpal bones below and on either side, and the tendon situated above. This is called the carpal tunnel or the carpal canal.
Passing through this tunnel are the transverse carpal ligament, tendons, and the median nerve. There is very little room and these ligaments and the median nerve fit tightly inside the tunnel.
If for some reason, the ligament or the tendons, which pass through the carpal tunnel get inflamed or edematous and swollen, they then press on the nerve. This results in the various carpal tunnel syndrome symptoms presenting themselves. These are the intrinsic factors, which act from within the tunnel that can compress the median nerve.
Extrinsic factors are factors that exert pressure from outside the tunnel. These are benign tumors such as lipomas, ganglion, and vasculature malformation.
There are various identifiable causes of carpal tunnel syndrome. At times, though, no cause can be identified. In such cases, it is likely that the carpal tunnel is smaller due to a congenital predisposition. This condition rarely occurs due to any cause in the median nerve, itself.
Any condition that decreases the size of the carpal tunnel or increases the size of the contents within it can cause this syndrome. At times, there may be a combination of factors or health conditions that cause the median nerve to get compressed and give rise to carpal tunnel syndrome.
1) Trauma to the wrist such as a fracture or dislocation, infection resulting from or burns or wounds, and injuries resulting from high-pressure injections of substances such as oil or paint can have a disastrous effect on the hand and can cause CTS.
2) Rheumatoid arthritis causes swelling of the synovium, which is a membrane that surrounds the tendons that run through the carpal tunnel. This exerts pressure on the median nerve and gives rise to the symptoms of carpal tunnel syndrome. Proper medications to control rheumatoid arthritis will control the symptoms.
3) Oral contraceptives or birth control pills contain estrogen and progestin or they may contain only progestin. They cause changes in the levels of the natural hormones in the body, which lead to fluid retention in the body. This may increase the pressure in the carpal tunnel and irritate the median nerve.
4) Menopause or perimenopause causes hormonal fluctuations in women. This leads to water retention (edema) in the body. As a result, nearly 90% of women put on weight during menopause. This weight gain is due to this fluid retention and decreased progestin levels.
Water retention occurs due to the fluid leaking from the blood into the body tissues, which become edematous.
Due to the tight squeeze in the carpal tunnel, any increase in pressure due to the edema in the tissues within it can cause compression of the median nerve. This can give rise to CTS symptoms.
5) Pregnancy is often associated with fluid retention and swelling in the body, including swelling of the hands. This increases the pressure in the narrow carpal tunnel, which puts pressure on the median nerve.
6) Obesity is often linked to carpal tunnel syndrome. Obesity and morbid obesity increase its risk by as much as 75-100%. Why this happens is not yet established.
However, it is known that obesity does cause an inflammatory state in our body tissues. This inflammatory process in the wrist could cause irritation of the median nerve and subsequently the CTS symptoms.
7) Hypothyroidism: Despite the strong link between carpal tunnel syndrome and hypothyroidism, research is still unable to determine why hypothyroidism causes CTS. However, hypothyroid patients are known to retain fluid in their connective tissue due to the accumulation of mucopolysaccharides.
Swelling of the connective tissues over the wrist can cause pressure on the median nerve and cause CTS symptoms. When hypothyroidism is treated, the symptoms of carpal tunnel syndrome improve.
8) Acromegaly is a hormonal disorder wherein the anterior pituitary gland produces an excess of the growth hormone.
Excess of growth of hormone prompts the tissues and the bones in the body to further grow beyond the normal size.
The extra growth of tissues and bones around the carpal tunnel compresses the median nerve.
9) Diabetes can cause carpal tunnel syndrome due to its complication of peripheral neuropathy. There is damage to the nerves often resulting in tingling and numbness of the affected part.
There are certain factors that do not directly cause carpal tunnel syndrome but increase the risk of developing CTS.
- Anatomical factors: Some people have a smaller carpal tunnel, where the risk of damaging or compressing the median nerve is more.
- Occupational hazards: Certain occupations in which there is long-term exposure to vibrating hand tools or where you have to repeatedly flex the wrist can increase your risk of developing CTS.
- Gender: Women suffer more than men from carpal tunnel syndrome. Being female increases your risk possibly due to a smaller carpal tunnel, hormonal changes during pregnancy, menopause, and oral contraceptives.
- Aging: Ageing does cause normal wear and tear of tissues in the body including those in the wrist. This can predispose to CTS.
Symptoms of Carpal Tunnel Syndrome
Symptoms of carpal tunnel syndrome develop gradually. They usually occur in both hands but are more pronounced in one hand. In most people, symptoms often start at night and they can wake you from sleep.
- You will experience stiffness, soreness and a burning sensation in the affected hand, wrist, fingers, and the forearm.
- Tingling and numbness (pins and needles sensation) in the hand particularly in the areas supplied by the median nerve. These areas include the thumb, the index finger, the middle finger and part of the fourth finger. You will not feel this symptom in the little finger because the median nerve does not cover it. These symptoms are more pronounced when gripping objects such as the steering wheel or the newspaper. They can even occur during sleep and wake you.
- Loss of strength in the affected hand leading to an inability to grip objects or drop them.
- You may feel the pain in the forearm and hand, which gets worse when you use the hand or wrist.
- Referred pain in the shoulder can also present.
Carpal tunnel syndrome symptoms in pregnancy
Most women develop swelling of the hands during pregnancy. This puts pressure on the median nerve giving rise to carpal tunnel syndrome symptoms of tingling and numbness in the hands and fingers.
About 60% of pregnant women develop carpal tunnel syndrome during pregnancy. Symptoms more commonly present during the second and third trimester of pregnancy
Tests and Diagnosis of Carpal Tunnel Syndrome
- Signs and symptoms which suggest carpal tunnel syndrome are very indicative of this disorder.
- X-ray of the wrist will help to detect any bone involvement such as fracture or arthritis.
- An abnormal nerve conduction test will strongly suggest CTS. In this test, the speed of the electrical impulse is measured as it passes down the nerve. In CTS, there is slowing of the impulse in the carpal tunnel.
- Electromyogram (EMG) measures the electrical activity of your muscles at rest and when contracting. This helps to assess muscle damage if any.
- Blood tests will determine any associated medical conditions such as diabetes and hypothyroidism that can cause CTS.
Treatment of Carpal Tunnel Syndrome
Treatment of carpal tunnel syndrome consists of treating the symptoms and removing the cause. It includes:
- Non-steroidal anti-inflammatory painkillers
- Rest to the part
- Use of a wrist splint to immobilize the wrist in order to prevent any more aggravation of the symptoms
- Application of occasional ice packs to reduce the inflammation
- Pyridoxine or vitamin B6 gives relief of symptoms
- In more severe cases, the doctor may advise oral steroids. At times, it may become necessary to inject steroids directly into the wrist to reduce the inflammation.
- Surgery for Carpal Tunnel Syndrome. Most cases recover with conservative treatment. In chronic cases, there is a risk of muscle wasting and continuous weakness and numbness. Surgery may then become necessary and it consists of relieving the pressure on the nerve by severing the carpal tendon. Exercise rehabilitation is also advised after the surgery. This procedure is called carpal tunnel release. Rarely, symptoms may recur.
- You should consult a doctor for any underlying cause of the carpal tunnel syndrome, such as disorders of the endocrine system and diabetes.
- If you are obese, reduce your weight.
- You should correct and modify any occupational reason for carpal tunnel syndrome. For example, if you operate vibrating hand tools for prolonged periods, you should refrain from doing that. Try and shift to another department or job.
Exercises for carpal tunnel syndrome
If you have carpal tunnel syndrome, exercises will most probably not benefit you. They may even worsen the condition. However, you can do nerve gliding or tendon gliding exercises in mild cases with other treatment options such as wrist splinting or after corticosteroid injections. You can also do these exercises post-surgery to prevent scarring of the nerve. Exercises are more beneficial to prevent carpal tunnel syndrome.