Abstract
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Objectives: Somatoform disorders (SFD) are characterized by somatic symptoms that are either very distressing or result in significant disruption of body functioning. Patients with SFD often exhibit high focus on their bodies, perceiving their bodily complaints quicker as illness than healthy people do. However the pathogenesis underlying SFD is largely unknown. In the present study, we intended to explore the abnormal brain metabolic pattern in SFD using 18F-FDG PET.
Methods: Eighteen SFD patients and twenty-one matched healthy controls (HCs) underwent 18F-FDG PET scanning. Two sample t test was performed to compare the group difference between SFD and HCs with age and gender entered as nuisance covariates using SPM12 (p <0.05 with FDR corrected, ke≥50 voxels). Then brain metabolic connectivity analysis was carried out to investigate the changes of brain organization in SFD with the seeds located at the significantly changed regions using AAL parcellation. Permutation test was performed to assess the differences of regional connections between groups with 1,000 permutations and the significant level was set at p < 0.05 for a 2-tailed test.
Results: Voxel-wise analysis between SFD and HCs revealed a significantly reduced glucose metabolism in SFD at bilateral insula and superolateral prefrontal cortex, including inferior frontal gyrus, middle frontal gyrus. In addition, hypometabolism was also found in the bilateral temporal gyrus, right angular gyrus, left gyrus rectus, right fusiform gyrus, right rolandic operculum and bilateral occipital gyrus; no hypermetabolism was found (Figure 1). Two significantly changed regions with maximum size and their contralateral areas in SFD, that is, bilateral insula and bilateral orbital part of inferior frontal gyrus (ORBinf), were chosen as the seeds for brain network analysis. Brain connectivity analysis revealed that left insula exhibited increased connectivity with right inferior occipital gyrus, left parahippocampal gyrus, right middle temporal gyrus and left superior temporal gyrus; and decreased connectivity with left insula and right postcentral gyrus, right supramarginal gyrus as well as left middle temporal gyrus. Right insula showed increased connectivity with bilateral median cingulate gyrus, right anterior cingulate, as well as left middle frontal gyrus, bilateral dorsolateral and medial part of superior frontal gyrus, and decreased connectivity with right middle temporal gyrus, left precentral gyrus, left postcentral gyrusand left heschl gyrus. Left ORBinf showed increased connectivity with right inferior occipital gyrus; decreased connectivity with left inferior parietal gyrus, left middle temporal gyrus and left heschl gyrus. While right ORBinf was found to have increased connectivity largely in prefrontal areas, including medial orbital part of left superior frontal gyrus, orbital part of left middle frontal gyrus, opercular part of left inferior frontal gyrus and orbital part of right superior frontal gyrus; and decreased connectivity with left heschl gyrus, left postcentral gyrus and left middle temporal gyrus (Figure 2).
Conclusions: Our study explored the abnormal brain glucose metabolism and connectivity pattern in SFD patients. Those findings would further our understanding about SFD, and help us to investigate the underlying metabolic neuromechanism of SFD.
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