"Fibromyalgia may be related to a global dysfunction of cerebral pain-processing," Guedj stated. "This study demonstrates that these patients exhibit modifications of brain perfusion not found in healthy subjects and reinforces the idea that fibromyalgia is a 'real disease/disorder.'"
Patients with fibromyalgia have characteristic changes in brain function that can be seen in single photon emission computed tomography (SPECT) scans, researchers here found.
Perfusion in the left and right parietal lobes, including pre- and post-central areas in the cortex, was positively correlated with scores on the Fibromyalgia Impact Questionnaire in a 30-person study (P<0.03), reported Eric Guedj, M.D., of the Hospitals of Marseille, and colleagues in the November issue of the Journal of Nuclear Medicine.
Abnormally low perfusion in a left anterior temporal cluster was also associated with increased scores on the fibromyalgia questionnaire (P=0.001). This hypoperfusion was most pronounced in the polar and mediobasal cortices.
Previous brain imaging studies have shown that the affected areas are involved with pain processing and emotional responses to pain.
As a result, according to Dr. Guedj and colleagues, the findings suggest that fibromyalgia is a disorder of central pain processing in which pain sensations are heightened.
These results may also explain why no musculoskeletal abnormalities have been found in fibromyalgia patients.
The study involved 20 female fibromyalgia patients and 10 healthy women of similar age. Diagnosis of fibromyalgia was made according to American College of Rheumatology criteria.
In addition to assessment with the fibromyalgia questionnaire, participants received other standardized psychometric evaluations: a visual analogue scale for pain, the Hospital Anxiety and Depression scale, the Questionnaire Douleur de Saint-Antoine scale, a French version of the McGill Pain Questionnaire, and the Tubingen Pain Behavior Scale.
Only the Fibromyalgia Impact Questionnaire scores were correlated significantly with the SPECT results, the researchers reported.
"The relationship between somatosensory hyperperfusion and fibromyalgia clinical severity is reported for, to our knowledge, the first time and reinforces the central sensitization hypothesis," they wrote.
The researchers added that low perfusion in the left anterior temporal region, part of the limbic system, may explain another aspect of fibromyalgia.
"Hypoperfusion of this area could be related to reduced affective appraisal and responsiveness, frequently observed in patients with fibromyalgia," they said.
They were uncertain as to why the SPECT findings failed to correlate with other measures of pain.
Visual analogue pain scores varied little among patients, which could explain the lack of correlation with the perfusion findings, they said.
But scores on the other pain scales showed higher variance than the Fibromyalgia Impact Questionnaire results.
Dr. Guedj and colleagues said the small number of participants was a limitation of the study. They also noted that, although fibromyalgia is often assessed with the general pain scales they used, "we should discuss… whether they are appropriate for such a use."
Bristol-Myers Squibb sponsored reproduction of color figures in the published article. No other funding was reported.
No potential conflicts of interest were reported.
Note that the findings need to be confirmed in larger numbers of patients before brain imaging can be used clinically to diagnose or monitor fibromyalgia.
Past imaging studies of patients with fibromyalgia had shown abnormalities in cerebral blood flow, also called brain perfusion. In some areas of the brain, blood flow was below normal, and in some areas, it was above normal. In this study, by using whole-brain scans on the participants, researchers were able to analyze how perfusion in each area of the brain related to measures of pain, disability, anxiety, and depression.
There seemed to be no relationship between these abnormalities and presence of depression or anxiety. "We found that these functional abnormalities were independent of anxiety and depression status," Guedj says in a news release.