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Brain activity reflects pain in Fibromyalgia
Monday 2 July 2012
A novel functional MRI approach that measures resting brain activity and connectivity may provide a much-needed objective measure of pain in patients with fibromyalgia, researchers suggested.
Pain treatment resulted in reduced resting, or intrinsic, connectivity between the brain's default mode network and the right anterior/middle insular cortex (z=3.63) in a group of 17 women with fibromyalgia, according to Vitaly Napadow, PhD, of Massachusetts General Hospital in Boston, and colleagues.
At the same time, clinical pain scores on a sensory subscale fell from a mean of 10.71 to 6.06 (P=0.02), and the diminished pain correlated positively with the reduced connectivity between the default mode network and the anterior insula (z=3.21), the researchers reported in the July issue of Arthritis & Rheumatism.
The widespread pain associated with fibromyalgia is thought to reflect hyperalgesia and discomfort resulting from stimuli not usually considered noxious.
Many studies have identified brain abnormalities in patients with fibromyalgia, but because the studies have been cross-sectional, "they do not address whether the changes in brain structure, function, and neurochemistry are a cause of the pain, a consequence, or simply factors associated with chronic pain," the researchers observed.
In previous work, Napadow's group used functional MRI to demonstrate that fibromyalgia patients show heightened intrinsic connectivity between the insula, which is involved in pain processing, and the default mode network, which centers on thoughts and memories of the self rather than external concerns.
However, that study too was cross-sectional and could not assess longitudinal changes in pain and response to treatment.
To address that gap, they recruited 17 female patients, mean age 46, who were participating in a study of nonpharmacologic treatment for fibromyalgia.
During the course of a month, the patients underwent nine sessions of acupuncture using a protocol that has shown efficacy for fibromyalgia pain, and had functional MRI scans done before and after the month of treatment.
The imaging was performed while patients rested quietly in the scanner, and linear regression analyses evaluated the changes in connectivity and pain ratings.
The treatment and MRI intervention were tolerated well by all patients.
Along with decreases on the sensory subscale of the McGill Pain Questionnaire, there also was a trend toward decreased pain on the affective subscale, from 2.24 to 1.35 (P=0.09).
MRI findings also included a reduction in the connectivity between the default mode network and the right putamen following treatment (z=−3.57), and diminished pain correlating with lower connectivity between the network and the left amygdala (z=3.22), the researchers reported.
In discussing their findings, they noted the importance of the default mode network in "self-referential cognitive processing."
"We could speculate that increased [default mode network]-insula connectivity in [fibromyalgia] may reflect a state of hyperawareness to pain, which has been incorporated into the patient's sense of self," Napadow's group wrote.
The study results suggest that imaging to assess intrinsic brain connectivity might be a sensitive candidate to serve as an objective marker for the assessment of treatment modalities.
"Incorporation of this marker in future clinical trials may provide a better understanding of the mechanistic pathways underlying various interventions," they concluded.
This study was supported by the National Center for Complementary and Alternative Medicine, the Department of the Army, and the Dana Foundation.
One co-author has received grants and fees from Cypress Biosciences, Eli Lilly, Forest Laboratories, Jazz Pharmaceuticals, Merck, UCB, Pierre Fabre Pharmaceuticals, and Pfizer, and another has received funding from Pfizer.
The above originally appeared here.
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