Multimodal Magnetic Resonance Imaging Study Of Somatic Symptom Disorder

Somatic symptom disorders(SSDs)are common medical disorders characterized by various biological,psychological,and social pathogenic factors.Little is known about the neural correlations of SSD.Several recent studies have reported a strong association between cerebellar structural and psychiatric disorders.However,no studies investigate possible structural changes and functional connectivity patterns in cerebellar regional gray matter volume associated with SSD.This study evaluated the dysfunction in 45 patients with SSD and 43 controls by combining the amplitudes of low-frequency fluctuation(ALFF)and regional homogeneity(ReHo)methods with resting-state functional magnetic resonance imaging.fALFF and DC analysis were used to detect the characteristics of spontaneous brain activity in SSD patients at resting-state.We employed two complementary studies,the SUIT cerebellar atlas-based voxel-based morphometry(VBM)and whole-brain VBM,to investigate the cerebellar regional gray matter(GM)changes.Seed-based functional connectivity(FC)analysis was further performed to investigate the pattern of abnormal FC across the whole-brain that are altered in parallel with the cerebellum.Correlations were calculated to investigate the relationships between cerebellar structure and neuropsychological tests.The patients with SSD exhibited significantly greater ReHo in the right cingulate gyrus and smaller ReHo in the right precuneus,left inferior and temporal gyrus extending to the left middle temporal gyrus and left parahippocampal gyrus,and right pons compared with the controls.The SSD patients showed higher ALFF values in the cingulate gyrus extending to the left medial frontal gyrus,right insula extending to the right inferior frontal gyrus,and left medial frontal gyrus extending to the left anterior cingulate cortex.Patients with SSD showed increased fALFF values in limbic lobe and thalamus compared with HCs.Besides,patients with SSD showed decreased DC values in the frontal lobe,cingulate gyrus.Compared to healthy controls,patients with SSD had increased gray matter volume in the bilateral cerebellum posterior lobe;specifically,Crus Ⅰ,Crus Ⅱ,lobule Ⅵ,Ⅷ,and Ⅸ area are the main statistically significant subregions.We also found increased FC between the left declive(Crus Ⅰ)and the CrusⅡ,parietal lobe,and frontal gyrus in patients with SSD.The degree of regional GMV increase in the significant posterior cerebellar clusters was correlated with the severity of clinical symptoms such as depressive condition and cognition scores(p=0.038 and 0.047,respectively).The cluster located in right lobules Ⅶa/crus Ⅰ,Ⅵ,and Ⅶa/crusⅡ(mainly right cerebellum posterior lobe)showed a correlation trend(p=0.094and 0.067 respectively)but did not yet reach a statistically significant.No significant correlation was found between the duration of disease and GMV.Other than that,no other statistically correlations were found.These dysfunction areas seem to have particular importance for SSD occurrence,which may result in dysfunction in self-relevant processes,emotional processing,multimodal integration,arousal,interoception,and body perception.Patients with SSD have recognizable and significant neuroanatomical differences in the bilateral posterior cerebellar lobe area,which may in part explain the pathophysiologic basis of the disorder.