Collaborations Chronic Pain
Pain is associated with a wide range of injury and disease, and is often the disease itself. Millions suffer from acute or chronic pain every year and the effects of pain exact a tremendous cost in the US, with estimates in the neighborhood of $5-600 billion annually in terms of both direct health care costs and the indirect costs due to lost productivity. One of the central issues in pain is understanding the source of the pain and the mechanisms responsible for it. There are currently no objective, standardized, quantitative methods for measuring the degree to which an individual’s CNS has been altered by their pain. Better diagnostic tools can lead to better and more effective treatments. Currently, we are studying several types of chronic pain in collaboration with the Center for Neurosensory Disorders at the University of North Carolina. The figure below exemplifies the impact that one type of pain (VVS: Vulvar Vestibulitus Syndrome; female pelvic pain) has on the individual’s brain health. Also note that there are significant differences in the results obtained between these subjects and control subjects in tests performed on the finger tips – a body site remote to the location of the pain. This is because the tests are designed to objectively assess cortical information processing.
Detecting the differences between peripherally and centrally mediated pain.
Patients who have chronic pelvic pain typically fall into two categories: those with “provoked” pain and those with “unprovoked” pain. The unprovoked pain is thought to be primarily centrally mediated, and the data in the figure supports this idea. Note that the adaptation metric for one patient group is significantly reduced from that of the other patient group, which is essentially the same as healthy controls. For more information, see Zhang et al, 2011.
Cortical Metrics are sensitive to different types of chronic pain. Using the methods described in Zhang et al, 2009, adaptation metrics were obtained at two different temperatures. Data (at right) shows that in non-fibromyalgia (FM) chronic pain subjects, there is no change in an already suppressed adaptation metric. However, in FM subjects, there is a reversal in the adaptation metric. That is, warming the forearm results in the FM subjects having a more typical “control-like” response. A better understanding of the fundamental mechanisms involved in tactile-thermal interactions may lead to better diagnoses and/or treatments of neurological disorders such as fibromyalgia.
Using a multi-parametric approach to analyze results from multiple cortical metrics leads to different characterizations of two different pain populations. The figure at left demonstrates this approach, distinguishing fibromyalgia (FM) from VVS subjects.