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Complex Regional Pain Syndrome Diagnostic Tests
Infrared Thermometry, Laser Doppler Flowmetry, and Infrared Thermography
These three diagnostic processes measure skin temperature differences, which track vascular movement (blood flow). The difference is in the method of tracking the incidence, sensitivity, and specificity of the temperature changes.
Infrared thermometry records the distribution of skin temperature. The most known use of this technology is for fever measurement, specifically ear and forehead thermometers. In CRPS testing, each area of the skin is then compared with the identical contralateral area (5).
Dutch treatment guidelines indicate that “a difference of 1.5°C [or 34.7°F] is recommended as a way of differentiating between normal posttraumatic syndromes and patients with CRPS” (12). Possible drawbacks of this kind of measurement include a low sensitivity; temperatures can vary from one point to another within the same area; and temperatures are not constant over time (12).
Laser doppler flowmetry measures the skin's "capillary blood flow to local thermal stimulation" (15). When a peripheral vascular disease is suspected, the blood flow deviates from the normal pattern, which also affects the skin temperature. Unlike thermography, which can measure a specific area, laser doppler flowmetry is more effective over a larger area. During laser doppler flowmetry, laser light is delivered to the tissue surface through an optical fiber, and the reflected light is collected by a second fiber, which is stored in a single probe (16).
A recent study involving different uses of laser doppler flowmetry found that CRPS is not associated with "the perfusion increase in patients' limbs, or between patients and healthy controls. The study found that CRPS was not associated with impairment of microvascular endothelial function. However, it was concluded that this may reflect the diversity of the CRPS disease process" (16). Basically, this diagnostic process only reflects impairment in some CRPS patients, but it does provide otherwise unknown insight into abnormalities in blood perfusion.
Infrared thermography uses an electronic thermographic apparatus to create computer-generated images that display changes in temperature. According to Philip Getson, DO, such "changes are controlled by the sympathetic nervous system and alterations in the sympathetics cause alterations in thermal (infrared) imaging which do not conform to [skin temperature] patterns." This testing is sensitive to skin temperature changes to one-tenth of one degree centigrade. (17)
In regard to CRPS, Dr. Getson claims that the lack of symmetry in skin temperature patterns confirms an initial clinical diagnosis. This temperature difference is often dramatic and using the thermal imaging camera is hundreds of times more sensitive than palpation alone (17).
According to Dutch treatment guidelines, infrared thermography is reliable for measuring diffuse versus local temperatures, and is good for testing temperature change due to hot and cold stimuli (12).
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Updated December 20, 2007 |
