Subgroups in Fibromyalgia
Fibromyalgia:
FMRI Evidence for
Increased Pressure Pain Sensitivity
R.H.
Gracely¹, F. Petzke², J.M. Wolf¹ and D.J. Clauw²
¹National Institutes of Health, Bethesda MD 20893 and ²Department of Medicine, Rheumatology
Georgetown University Medical Center, Washington D.C. 20037
INTRODUCTION:
Fibromyalgia is characterized by subjective reports of increased tenderness
and sensitivity to pressure stimuli suggestive of allodynia. We evaluated
pain-evoked activity in brain structures produced by equally painful pressure
in 21 patients meeting ACR criteria for Fibromyalgia and in 16 control
subjects.
HYPOTHESIS:
Subjectively equivalent painful stimulation, produced by significantly
less pressure in patients, will produce similar patterns of cerebral activation
in both groups.
PROCEDURES:
a 1.5 Tesla EPI BOLD method acquires complete head volumes (50-alice,
3-mm cubic voxels) at 5-sec intervals. Thirty seconds of intensely painful
stimuli (1-cm² probe applied to thumb) alternated with 30 sec of innocuous
stimulation for 10 cycles.
SUMMARY
OF RESULTS: Equally-painful stimuli significantly increased regional
cerebral blood flow (rCBF) in common regions including contralateral primary/supplemental
sensory cortex (SI/SSS, secondary somatosensory cortex/retro insular parietal
operculum (SII, RI-PO), putamen, insular cortex, superior temporal gyrus
(BA22,38) and ipsilateral anterior cerebellum. Stimuli of similar physical
intensities activated similar regions in insular cortex. Painful stimulation
in patients resulted in significantly less activation in regions of bilateral
anterior cingulate cortex (ACC), caudate nucleus and thalamus, and increased
activation in a specific region of ipsilateral caudate.
CONCLUSIONS:
Activation of similar regions by equally-painful (although different intensity)
stimuli suggests a cortical or subcortical amplification. Activation of
similar regions in the insula in all conditions is consistent with multi-modality
processing observed in previous functional imaging of supraspinal pain
activation. The relative lack of response of thalamus and caudate in patients
is consistent with previous results showing tonic reduced activity in
these structures in patients. The reduced patient response in ACC is not
consistent with previous findings of increased ACC activity in patients.
Additional studies are needed to confirm and extend these findings.
KEYWORDS:
Pain, neuroimaging, mechanisms
This work in the abstract was supported
in part by a grant from the National Fibromyalgia Research Association.
Presented at the National Fibromyalgia
Research Association's Subgroups in Fibromyalgia Symposium, September
26-27, 1999, in Portland, Oregon.
