Changes in gray matter density in fibromyalgia: correlation with dopamine metabolism

Fibromyalgia (FM) has been associated with alterations in brain morphometry and abnormal dopaminergic neurotransmission. Evidence from preclinical models has demonstrated that dopamine plays a role in promoting neuronal integrity. We therefore sought to confirm previous findings of reduced gray matter density in subjects with FM and to determine whether variations in dopamine metabolism might affect gray matter density. Voxel-based morphometry was used to evaluate anatomical magnetic resonance imaging data from 30 female FM subjects in comparison with 20 age- and gender-matched healthy control subjects. In addition, data from a subset of subjects from both groups who had previously participated in our positron emission tomography study using radiolabeled DOPA (n = 14; 6 FM subjects and 8 control subjects) was used to determine whether correlation might exist between gray matter density and dopamine metabolism. We found a significant reduction in gray matter density within the bilateral parahippocampal gyri, right posterior cingulate cortex, and left anterior cingulate cortex. In addition, a positive correlation was demonstrated between an index of dopamine metabolism from the ventral tegmental area wherein cell bodies of corticolimbic projection neurons originate and gray matter density, specifically in the bilateral parahippocampal gyri and left pregenual cortex. The current results confirm our previous findings that FM is associated with altered brain morphometry. Alterations in dopamine metabolism might contribute to the associated changes in gray matter density.

Fibromyalgia is associated with reductions in gray matter density within brain regions ostensibly involved in phenomena related to the disorder, including enhanced pain perception, cognitive dysfunction, and abnormal stress reactivity. Given mounting evidence of abnormal dopaminergic neurotransmission associated with the disorder, the strong correlation between dopamine metabolism and gray matter density provides insight as to the pathophysiology that might contribute to these changes.