Repetitive stress injuries
Carpal tunnel syndrome is most accurately diagnosed using the patients' descriptions of symptoms, and electrodiagnostic tests that measure nerve conduction through the hand. If electrodiagnostic testing is not available, symptom descriptions and a series of physical tests are useful.
Diagnosing CTS, however, is not straightforward. Only a small fraction of patients exhibit all three factors necessary for a clear diagnosis:
Many people have abnormal electrodiagnostic test results without classic symptoms or any symptoms at all. Furthermore, about 15% of the population has symptoms consistent with CTS, but most do not show test results indicating the disorder.
Many cases of CTS result from a combination of a medical problem exacerbated by repetitive stress factors at work. The patient should give the doctor a detailed history and description of any complaints, in any part of the body. The patient should report in detail any daily activities that require repetitive hand or wrist actions, abnormal postures, or other regular situations that could affect the nerves in the neck, shoulders, and hands. The patient should also report whether the symptoms are more likely to appear at night, or after particular tasks.
Questionnaires. The use of specific questionnaires that score results are quite accurate in assessing the severity of the condition.
Hand Diagram. A diagram of the hand and wrist, usually divided into six regions, is a very useful diagnostic tool. Patients are asked to indicate where their symptoms are, including pain, numbness, or tingling, by locating the affected areas on the diagram. They may also be asked to rate the severity of their symptoms. A diagnosis is probable if at least two of fingers 1, 2, or 3 have these symptoms, and if there is pain in or near the wrist. CTS is possible if at least one of these fingers has symptoms. It is unlikely if there are no symptoms in these fingers, the palm, or the wrist.
One of the most important first steps in diagnosing CTS is to rule out any underlying medical disorders that may be contributing to the condition. Experts emphasize the need to fully examine patients presenting with symptoms of CTS. Relying only on CTS symptoms, and personal or work histories may result in the failure to detect (and thus properly treat) underlying medical conditions that could be serious. If the doctor suspects that an underlying medical condition may be exacerbating the symptoms of CTS, laboratory tests will be performed. Tests for thyroid disease and rheumatoid arthritis may be helpful. The doctor may take an x-ray, for example, to check for arthritis or fractured bones.
Arthritic Conditions. Arthritic conditions, including rheumatoid arthritis, gout, and osteoarthritis, can all cause pain in the hands and fingers that may mimic carpal tunnel disease. The treatment for these conditions, however, is different.
Muscle and Nerve Diseases. Any disease or abnormality that affects the muscles and nerves, including those in the spine, may produce symptoms in the hand that mimic carpal tunnel syndrome.
About 25% of patients with suspected work-related cumulative trauma or repetitive stress disorders have evidence of other conditions that resemble, but are not, carpal tunnel syndrome. A definitive diagnosis is often difficult. Most require treatments similar to those used for CTS: rest, immobilization, steroid injections, and even surgery if conservative treatment is unsuccessful.
Other Cumulative Trauma Disorders
The Median Nerve in Other Locations
Repetitive work can cause pressure on the median nerve in locations other than the wrist and can also affect other nerves in the arm and hand. The branch of the median nerve that runs through the palm of the hand can be damaged directly by repeated pounding or by the use of certain tools requiring a strong grip using the palm, such as needle-nosed pliers. The median nerve can also be pinched in the forearm.
Guyon Canal Syndrome (Commonly called ulnar tunnel syndrome)
The ulnar nerve can, like the median nerve, can be trapped as a result of repetitive stress. When this nerve is trapped, the condition is sometimes referred to as ulnar tunnel syndrome. It is more correctly known as Guyon canal syndrome, however, since this is the name of the passage through which the ulnar nerve passes.
General symptoms are similar to carpal tunnel syndrome, but patients experience loss of sensation in the ring and little finger and in the outer half of the palm. It can be a separate problem, although it commonly occurs with CTS. In such cases, release surgery for CTS usually also relieves the ulnar nerve entrapment.
The ulnar nerve can also be affected at the elbow.
De Quervain's Tenosynovitis
Tenosynovitis is swelling of the slippery covering of the tendons that move the thumb. When it causes pain on the side of the wrist and forearm right below the base of the thumb, it is known as De Quervain's tenosynovitis. (Finklestein's Test may help identify this. Make a fist that encloses the thumb, and bend the wrist sideways and down away from the thumb. If it causes pain, it is likely to be De Quervain's tenosynovitis.) It may be treated with splints or corticosteroid injections. In severe cases release surgery is effective.
Digital Flexor Tenosynovitis (Trigger or Snapping Finger)
Digital flexor tenosynovitis, commonly called trigger or snapping finger, is brought on when a tendon thickens, leaving the finger or thumb in a bent position. This disorder usually occurs when the tendons form a knot and may arise in those with hypothyroidism, diabetes, gout, rheumatoid arthritis, or connective tissue disorders. It can cause pain and a clicking sound when the trigger finger or thumb is bent and straightened. It can be effectively treated with corticosteroid injections.
Thoracic Outlet Syndrome
Thoracic outlet syndrome is caused by compression of nerves or blood vessels running down the neck into the arm. It can produce symptoms very similar to CTS. Other symptoms may include Raynaud's phenomenon (changes in sensation and temperature in the hand). The compression occurs at the first rib in the front of the shoulder. This may happen after an accident or simply from chronic slouching posture. A doctor may be able to diagnose the condition by detecting diminished blood flow in the arm as the patient raises the affected hand and turns his or her head toward the opposite side. Although the condition is uncommon, a correct diagnosis is important to differentiate it from CTS, since treatments differ. Surgery may be required to relieve pressure on the nerves and blood vessels.
The following findings are helpful in identifying carpal tunnel syndrome:
Flick Signal. One important and simple test of carpal tunnel is the "flick" signal:
Testing for Thumb Weakness. Two questions are useful in determining thumb weakness:
Provocation Tests. Certain tests can produce symptoms:
Hand Elevation Test. The patient raises their hand overhead for 2 minutes to produce symptoms of CTS. The test was recently proven to be accurate and may provide useful information when combined with the Tinel's and Phalen's tests.
Electrodiagnostic tests analyze the electric waves of nerves and muscles. These tests can help detect median nerve compression in the carpal tunnel.
Electrodiagnostic tests are the best methods for confirming a diagnosis of CTS at this time. Doctors who perform these tests should be certified by the American Board of Electrodiagnostic Medicine, which uses rigorous standards in qualifying doctors. Specific electrodiagnostic tests, called nerve conduction studies and electromyography, are the most common ones performed: Nerve conduction tests can also detect causes of symptoms that mimic CTS but are caused by other problems, such as pinched nerves in the neck or elbow, or thoracic outlet syndrome.
While electrodiagnostic studies are frequently done to confirm the diagnosis of carpal tunnel syndrome in patients with classic symptoms, they are also performed on patients with symptoms that do not point to carpal tunnel syndrome as clearly. Doctors must interpret test results in these patients more carefully.
Portable electrodiagnostic testing. Portable electronic devices are being evaluated for measuring nerve conductivity. They are relatively quick and easy to use on a large scale in an industrial facility. However, these devices are not well studied in clinical trials.
Limitations. Electrodiagnostic studies are not well standardized, and certain conditions can skew the results of either test:
Ultrasound. Studies of ultrasound accuracy in CTS diagnosis yield mixed results. In addition, there are no accepted standard diagnostic criteria for carpal tunnel syndrome using ultrasound.
MRI. Magnetic resonance imaging (MRI) has been studied as a tool to evaluate the median nerve. It requires special expertise, has limited diagnostic accuracy, and is still too expensive for routine use. Electrodiagnostic tests remain the preferred method of diagnosis. MRI may be most effective for detecting any internal injuries, tumors, arthritis, or joint damage that might be causing the problem. It may also be valuable in selecting surgical candidates when electrodiagnostic tests produce unusual results or indicate more severe disease than expected. Additionally, an MRI may be useful for evaluating patients if surgery fails to bring relief.
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