Different areas of the brain are active in different chronic pain conditions, and now researchers have shown that those areas are distinctly different in patients with interstitial cystitis and chronic prostatitis/chronic pelvic pain syndrome.
Chicago-In chronic pain conditions, specific brain areas are active, but not the same ones for each condition. Now Northwestern University researchers have shown that those areas are distinctly different in patients with interstitial cystitis and chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS).
At the AUA annual meeting, Anthony J. Schaeffer, MD, reported on his collaboration with physiologist A. Vania Apkarian, PhD, to study brain activity in patients with CP/CPPS and IC as well as the effects of chronic pain on their cognitive function. Dr. Schaeffer is professor and chairman of urology and Dr. Apkarian is professor of physiology at Northwestern University's Feinberg School of Medicine, Chicago.
Seven men with CP/CPPS, one man with IC, and two women with IC underwent functional MRIs (fMRIs) of the brain. During imaging, as pain fluctuated, patients moved their finger and thumb together or apart to indicate the degree of pain they experienced, which was recorded on a computer.
The practical question, Dr. Schaeffer pointed out, is what role these brain areas play. "It turns out," he said, "that they affect decision-making under stress."
Thus, investigators used a standard test of decision-making (a card gambling test) to see how the CP/CPPS and IC patients would perform. Similar to other patients with chronic pain syndromes, the patients had a dramatically reduced ability to make the correct choice in that stressful situation. Patients also had impaired ability to recognize emotion in a test of recognition of facial expressions, a test that has not been used in other chronic pain conditions, Dr. Schaeffer noted.
"These findings would be examples of how the central nervous system deficiency is correlated to functional impairment," he said.
Dr. Schaeffer hopes these studies will help define these two disease states. They have been known as syndromes without strong definitions. In fact, many urologists researching them think they may be the same condition. But this research may not only show them to be distinct; it may also help define the disease state with specific, identifiable anatomic and functional abnormalities.
"This, then, could pave the way for mechanistic studies and eventually therapies that could be designed to alter these mechanism deficiencies," he said.
Subgroups may hold key
Interestingly, abnormalities in subcortical brain structures, such as those identified in this study, and in N-methyl-D-aspartate (NMDA) receptors have been identified in other chronic pain conditions, noted Jordan Dimitrakov, MD, PhD, instructor in surgery at Harvard Medical School, Boston. Studies such as this, he said, could define a distinct patient group that could then be studied for the molecular and biochemical abnormalities and that could point to effective drug targets for pain.