A new brain imaging study reveals that patients with fibromyalgia (FM) show unique brain activity in response to pain. The patients had increased connectivity between the primary region of the brain that recognizes touch, the S1 somatosensory cortex, and a second region that assigns salience to stimuli, the anterior insula.
The results suggest "a neurobiological substrate for evoked pain hypersensitivity in FM," the authors report.
In the study, published online January 26 in Arthritis & Rheumatology, Jieun Kim, PhD, from the Massachusetts General Hospital/MIT/Harvard Medical School Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, Massachusetts, and the Division of Medical Research, Korea Institute of Oriental Medicine, Daejeon, Korea, and colleagues compared 14 healthy control patients with 35 patients with FM.
They found that patients with FM showed increased connectivity between the S1 and the anterior insula in response to pain compared with healthy control patients. The connectivity changes correlate with how much clinical pain the patients reported before functional magnetic resonance imaging (fMRI).
The researchers also saw an association between the S1/anterior insula connectivity and pain catastrophizing and temporal summation, both of which are features of FM.
"The anterior insula is a very important structure for pain and a very important signal for salience, for how much you're attending to a sensation," coauthor Richard E. Harris, PhD, assistant professor, Department of Anesthesiology, Chronic Pain and Fatigue Research Center, University of Michigan Health Center, Ann Arbor, told Medscape Medical News. His group has previously reported increased connectivity between the insula and the default mode network in patients with FM.
"This paper highlights the fact that the somatosensory cortex and connectivity to the insula related to pain administered in the study is also related to clinical pain," Dr Harris told Medscape Medical News. "This suggests that the fMRI outcome is also related to clinical pain."
Test participants were fitted with a blood pressure cuff on the lower leg. Each patient was tested to see how much pressure caused them to report pain of 40 on a 0 to 100 pain scale, with 0 being no pain and 100 representing the most intense pain tolerable. At a later date, during fMRI tests, experimenters used a blood pressure cuff fitted to the lower leg for two 6-minute intervals of pain meeting the previously determined 40-point level. Test participants also completed a series of questionnaires including the Pain Catastrophizing Scale, the Beck Depression Inventory, and the Brief Pain Inventory.
"I think it's a remarkable paper," Lesley M. Arnold, MD, professor of psychiatry and behavioral neuroscience and director of the Women's Health Research Program at the University of Cincinnati College of Medicine in Ohio, told Medscape Medical News. "It's an important contribution to the understanding of mechanisms involved in chronic pain conditions. I think it has shown us the neurobiological mechanisms underlying the pain that patients report."
"I think the bottom line is, sometimes the patients with [FM] experience pain and they feel like physicians aren't really acknowledging the pain they feel. You can't see the disorder. There's no obvious injury. But here we have a study that illuminates that the brain is functioning differently in [FM]. It legitimizes for patients that there is something different about their brain, and it might offer ideas of how we might treat the condition. Can we change this to function more normally? Can we change the connectivity through medication or therapy?"
Senior author Vitaly Napadow, PhD, LicAc, associate professor, Harvard Medical School, and director of Harvard's Center for Integrative Pain NeuroImaging, said looking at treatment is the next step. His group plans to use fMRI to see how patients respond to cognitive behavioral therapy, which has brought relief for some patients.
"What is it about the brains of some patients that keeps them from responding to cognitive behavioral therapy, and would they respond to some other therapy? If you know the biological underpinnings, you might be able to better design a therapy that [induces better responses]. And that's ultimately our goal."
Dr Napadow told Medscape Medical News.
Sammy Metras, MD, assistant clinical professor of rheumatology at the University of Southern California in Los Angeles is a practitioner who sees many patients with FM. He says the study may go a long way into showing FM skeptics that there is a biological basis for the symptoms their patients' experience. "Sometimes people say, 'It's in your head.' fMRI proves it's a real disease with connections between all these symptoms. It will help me convince the patients' primary doctor that this is a real disease."
Dr Arnold and Dr Metras have disclosed no relevant financial relationships.
Arthritis Rheumatol. Published online January 26, 2015. Abstract
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Cite this: Fibromyalgia Imaging Study Shows Unique Brain Connectivity - Medscape - Feb 10, 2015.