Clin J Pain. 2015 Sep 3. [Epub ahead of print]
Shokouhi M, Davis KD, Moulin DE, Morley-Forster P, Nielson WR, Bureau Y, St Lawrence K.
Pain disability is a major impediment to fibromyalgia (FM) patients' quality of life. Neuroimaging studies have demonstrated abnormal pain processing in FM. However, it is not known whether there are brain abnormalities linked to pain disability. Understanding neural correlates of pain disability in FM, independent from pain intensity, could provide a framework to guide future more efficient therapy strategies to improve patients' functional ability.
We used arterial spin labeling to image cerebral blood flow (CBF) in 23 FM patients and 16 controls. Functional connectivity was also estimated using blood oxygenation level dependent (BOLD) imaging to further investigate the possible underpinnings of the observed CBF changes.
Among patients, CBF in the basal ganglia correlated negatively with pain disability index (PDI) and positively with the overall impact of FM (fibromyalgia impact questionnaire) but did not correlate with pain intensity. Whole-brain analysis revealed no CBF differences between the two groups; however, post-hoc analysis in the basal ganglia showed CBF reductions mainly in the right putamen and right lateral globus pallidus in patients, likely reflecting the negative correlation with the PDI. However, the connectivity of the corresponding cortico-basal ganglia-thalamus loop, i.e. motor network (the connection between supplementary motor area, putamen and thalamus) remained intact.
Basal ganglia perfusion reflects long-term symptoms, including somatic and psychological components of FM rather than pain intensity. These CBF findings may reflect differences in behavioral and psychological responses between patients.