Carpal tunnel syndrome is due to squeezing of the median nerve as it passes through the wrist to the hand. This nerve is contained in the carpal tunnel, a narrow channel just above the wrist. In carpal tunnel syndrome, the channel starts to shrink, compressing the nerve and causing inflammation. The result is hand pain, numbness, tingling, and sometimes, hand weakness or restricted movement. The ring finger and little finger are usually spared.
Carpal tunnel syndrome is one of the most common causes of claims for workers' injury compensation, second only to lower back pain. Women are at three times greater risk of developing carpal tunnel syndrome compared to men. It occurs at any age, but is more common in people over 50 years old.
The median nerve carries messages between the thumb, index finger, middle finger, and the brain. Pain, touch, and sensation are transmitted to the brain and instructions to move muscles are sent from the brain.
The transverse ligament runs across the inside of the wrist like a watch strap. The carpal tunnel is the space between this and the bones on the outside of the wrist. The tendons, muscles of the fingers, blood vessels, and nerves pass through it. The median nerve lies on top of them on the inside of the wrist. There is just enough room for it between the tendons and the transverse ligament.
Carpal tunnel syndrome results when there is increased pressure on the median nerve and tendons within the carpal tunnel. It is usually a combination of things that causes the increased pressure. Factors that contribute to the development of carpal tunnel syndrome include:
- trauma or injury to the wrist
- certain medical conditions (e.g., rheumatoid arthritis, hypothyroidism or underactive thyroid, diabetes)
- repetitive movements of the hand or wrist
- cysts or tumours
- frequent use of vibrating hand tools
- having wrists too small for all the ligaments and nerves to fit properly
In many cases, the exact cause cannot be determined.
Symptoms and Complications
Symptoms are caused by the pinched median nerve in the carpal tunnel. People with this condition may experience:
- numbness in two or more fingers
- pain that can extend into the elbows
- tingling or burning sensations in the hand (from thumb to middle fingers), wrist, and forearm
- inability to feel the difference between hot and cold
- difficulty gripping small objects
- fingers feeling swollen
Most people first realize something is wrong when they wake up one night feeling that their hand is asleep, yet painful at the same time.
Making the Diagnosis
To diagnose carpal tunnel syndrome, your doctor will perform a physical exam and may perform some tests. Your doctor will ask you about your symptoms and will examine your hands, arms, shoulders, and neck. Your doctor will check for tenderness, swelling, and sensation. If your whole hand feels numb and painful but you have feeling in the little finger, there may be a median nerve problem (the median nerve doesn't connect to the little finger).
A doctor might tap your wrist gently with a reflex hammer in an attempt to trigger the symptoms. Your doctor may also ask you to hold your arms forward and bring the backs of your hands together, or to bend your wrists with your fingers pointing downward. Tingling or numbness that is felt within one minute of assuming these positions is suggestive of carpal tunnel syndrome.
An electronic test can provide a definitive diagnosis of a problem with the median nerve. This is called a nerve conduction test and it helps your doctor decide how serious the damage to the median nerve may be.
Treatment and Prevention
First, your doctor will treat any underlying problems (e.g., diabetes, arthritis). Your doctor may also recommend resting the hand and wrist, and using a brace or splint, especially when sleeping. These can prevent further injury to the median nerve.
Medications can help the pain and inflammation associated with carpal tunnel syndrome. Pain medications might be recommended or prescribed by your doctor, including acetaminophen*, ibuprofen, naproxen, or acetylsalicylic acid (ASA). Occasionally, corticosteroids are injected into the carpal tunnel to ease swelling and relieve pain. Your doctor may also recommend applying heat to help with pain or cold to help with pain and swelling.
Very severe cases might require an operation on the hand. Carpal tunnel release surgery is done on the wrist and forearm. The surgeon cuts the transverse ligament that is pressing on the nerve. The gap fills with scar tissue and the pressure is relieved. Once the nerve is no longer being "pinched," the pain usually goes away and the hand can function normally again.
Pregnant women who experience carpal tunnel syndrome often improve a short time after the delivery of their baby.
Improving the comfort level and ergonomics of the workplace can also be very effective. This may include stretching exercises, taking frequent breaks, using proper posture, and repositioning your keyboard. People who do a lot of work on computers should be especially aware of things they can do to avoid overuse of their joints, muscles, and ligaments – especially the wrists.
Certain complementary and alternative medicine, such as chiropractic treatments, may help in providing relief from carpal tunnel syndrome. There is some evidence that supports the use of manual and manipulative therapy and full kinetic chain therapy combined with exercise to manage carpal tunnel syndrome.
*All medications have both common (generic) and brand names. The brand name is what a specific manufacturer calls the product (e.g., Tylenol®). The common name is the medical name for the medication (e.g., acetaminophen). A medication may have many brand names, but only one common name. This article lists medications by their common names. For information on a given medication, check our Drug Information database. For more information on brand names, speak with your doctor or pharmacist.