Thermographic correlates of chronic pain: analysis of 125 patients incorporating evaluations by a blind panel.

Series of thermograms from 125 sequential participants were analyzed to determine the usefulness of thermography as a tool for evaluating chronic pain. The stability and symmetry of thermographic patterns over time among both healthy subjects and subjects whose pain remained at the same intensity across several recordings were found to be both high and consistent. This was true only if sensitivity was limited to no greater than 0.5C per color band. Greater sensitivity resulted in the creation of inconsistent asymmetrical patterns among healthy and pained subjects. Thermograms were evaluated by the authors' statistical analysis of the heat patterns and by a ten-member panel of scientists. They found thermography an excellent tool for monitoring changes in pain related to variations in near surface blood flow, such as those occurring during a sympathetic block. It was excellent for relating changes in near surface blood flow to changes in phantom limb pain intensity. There was a good relationship between changes in pain intensity and changes in symmetry of heat patterns for most of the disorders examined. Thermography had mixed usefulness in differentiating pain-free from pained subjects reporting knee pain (test efficiency, 98%), leg pain, and back pain (efficiency, 56%). It consistently indicated painful areas among patients with spinal cord injury.