Posted on Feb 24, 2009

Following are the most common diagnostic tests used to aid in the diagnosis of CRPS. Response to sympathetic blockade In the past, physicians believed that a positive response (reduced pain) to a sympathetic block was necessary to make the diagnosis of CRPS. This is no longer considered to be the case. Tests of sudomotor functioning During any stage of CRPS, patients may have abnormalities in sweat gland function (called sudomotor function). Patients may have either excessive or reduced sweating. Special laboratories are able to test resting sweat output (RSO), thermoregulatory sweating (TST) and quantitative sudomotor axon reflex testing (QSART). These tests are helpful if they are positive, but not if they are negative. Sudomotor functioning tests are difficult to conduct and available in only a few parts of the country. Three-phase bone scans Once the only diagnostic tool available to doctors, this test has proven to be of limited usefulness. It becomes positive in only approximately 50% of CRPS patients (usually in later stages of the illness) and is, therefore, not particularly useful in making the diagnosis in earlier stages. Nerve conduction testing (NCV) and electromyography (EMG) Despite the fact that EMG/nerve conduction testing is very common, there are actually very few studies about their usefulness in patients with CRPS. Studies that do exist show that there are nerve conduction abnormalities in almost half of CRPS patients, but the abnormalities tend to be mild. Some researchers have suggested that the abnormalities may be due to swelling (called edema) or changes in blood supply to affected limbs, which then affects nerve functioning. A specialized test of nerve conduction is called somatosensory evoked potentials (SEP). Like other nerve conduction tests, there may be borderline abnormal findings in CRPS patients and the tests may be misinterpreted. SEP recording is not recommended as a routine method to diagnosis of CRPS-I. Based on these mild or borderline abnormalities, some test readers (called electromyographers) may make the mistake of saying that patients have "peripheral neuropathy," which is a different disease process than CRPS. The exception to this is when a patient does have a definite nerve injury associated with CRPS (CRPS-II). Nerve conduction testing uses skin electrodes placed on the surface of the skin and usually is not painful. Electromyography, on the other hand, uses needles that are placed within muscle tissue and is painful. EMG recordings are generally not helpful in CRPS patients and may worsen CRPS. Experts generally agree that EMG recordings have no diagnostic value in CRPS. Quantitative sensory testing (QST) QST may be a useful method for a physician to confirm the clinical findings of abnormalities in sensation. The problem with this test, however, is that it is not specific for the disease CRPS. It may help, however, to confirm the doctor's findings, particularly when multiple physicians have recorded a wide variety of findings on testing sensation. These tests are available in only a few parts of the country. Sympathetic skin response (SSR) These tests may help confirm the doctor's impression that there are "sympathetic" abnormalities in function, however, it is a very specialized type of test done in only a few laboratories that conduct other electrical testing such as electromyography and nerve conduction. So far, it is of unproven value and not generally recommended for making the diagnosis of CRPS. Other radiological imaging studies Plain x-rays and MRI scans may occasionally be useful, particularly in later stages of the disease. MRI can demonstrate the presence of soft tissue changes such as swelling or skin thickening. Plain x-rays may show demineralization of bone in later stages of CRPS. For these reasons, imaging tests can be useful in later stages of CRPS but not as a screening tool earlier on. **Infrared thermography Infrared thermography is a diagnostic imaging procedure that records body surface temperature by detecting the heat (infrared radiation) emitted from the surface of the skin. An infrared thermogram essentially is a "heat map" of the surface of the skin. This heat map accurately records changes in skin blood flow. By evaluating alterations of the surface skin temperatures, a physician is able to indirectly evaluate the neurological status of the autonomic nervous system. This information may be very helpful, as the autonomic nervous system is intimately involved in both CRPS type I, CRPS type II and other painful conditions that can mimic CRPS. Symptoms The main symptom of complex regional pain syndrome is intense pain, often described as "burning." Additional signs and symptoms include: Skin sensitivity. Changes in skin temperature, color and texture. At times your skin may be sweaty; at other times it may be cold. Skin color can range from white and mottled to red or blue. Skin may become tender, thin or shiny in the affected area. Changes in hair and nail growth. Joint stiffness, swelling and damage. Muscle spasms, weakness and loss (atrophy). Decreased ability to move the affected body part. Complex regional pain syndrome typically has three stages, though not everyone progresses through these phases at the same pace: Stage 1. Severe pain develops in one of your limbs. Swelling, sensitivity to touch or to cold, and skin changes, such as drying or thinning, begin to appear. This stage usually lasts one to three months. Stage 2. Changes to the color and texture of your skin become increasingly obvious, and the swelling spreads. You may begin to feel stiffness in your muscles and joints. This stage may last three to six months. Stage 3. Severe damage is evident, such as limited movement in your affected limb, irreversible skin damage, muscle atrophy and contractures in nearby digits.