What Is Carpal Tunnel Syndrome?
Carpal tunnel syndrome is a painful compression of a nerve in the wrist. It affects between 4 and 10 million Americans, according to the multiple studies. While the exact cause of carpal tunnel syndrome is usually unknown, it results from a narrowing of a portion of the wrist anatomy called the carpal tunnel.
The carpal tunnel is a narrow space in the wrist. The bottom and sides are made of small wrist bones known as carpal bones, and the “roof” of the tunnel is made of a stiff ligament. Through the tunnel passes a number of tendons and, crucially, the median nerve–one of the main nerves of the hand that provides feeling in all fingers but the pinky and also controls the muscles around the thumb.
If the carpal tunnel is or becomes narrow, or if the tissues inside the tunnel swell, it has the potential to compress the median nerve. This causes pain, tingling, numbness or weakness of the hand. Long term compression can lead to irreversible muscle atrophy and weakness.
Carpal tunnel syndrome is often thought of as a condition that mainly affects people who work at a computer, but that’s not necessarily true. People who work in occupations that involve a lot of repetitive hand movement, like cashiers and hairdressers, as well as occupations that expose the hands to vibration, such as working with power tools, are at a much greater risk of carpal tunnel syndrome than those who work at jobs that call for continuous typing.
Women are at greater risk of carpal tunnel syndrome than men because their wrists are generally smaller, and consequently their carpal tunnels are narrower to begin with. Other risk factors include:
- Rheumatoid arthritis
- Underactive thyroid
- Use of oral contraceptives
- Wrist fractures
Carpal tunnel syndrome usually affects the thumb, index and middle fingers as well as half of the ring finger. Symptoms include:
- Difficulty performing fine motor movements with the affected hand
- Pain or burning
- Weakness in the hand
The doctor will usually start with a medical history, listening to the patient’s description of symptoms, and then perform a physical examination that may include bending the wrist at 90 degrees or tapping the wrist.
Another diagnostic tool is the two-part nerve conduction test. The first part involves placing an electrode on the wrist, through which a mild electrical current flows, stimulating the median nerve. As the current flows through the nerve, the doctor measures how long it takes for the electrical impulse to reach the hand. The longer this takes, the more likely it is that the median nerve is damaged or compressed.
The second part of the nerve conduction test, electromyography, measures muscle function. A needle is inserted into various muscles influenced by the median nerve, and their electrical impulses are measured. Compression of the median nerve will impair these impulses.
Imaging studies, such as ultrasound and magnetic resonance imaging (MRI), are usually not necessary for diagnosis.
Carpal tunnel syndrome can be treated surgically or nonsurgically. Conservative, nonsurgical treatment options include:
- A nighttime brace or splint
- Adjustments in activities or workspace
- Over-the-counter pain medications, such as nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen
- Physical therapy
- Steroid injections
The main form of surgical treatment is called carpal tunnel release. It can be done endoscopically–with a number of small incisions, small tools and a flexible camera attached to a video monitor–or as an open procedure, with a similarly sized incision. No significant differences exist between the two varieties of a carpal tunnel release.
In either case, the surgeon divides the ligament, called the transverse carpal ligament, that acts as the roof of the carpal tunnel. The goal of this is to make more room in the tunnel and alleviate the pressure on the median nerve. The ligament may eventually grow back together or scar in, but it should grow in such a way as to allow more space within the tunnel.
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