Application Of Resting-State Fonctional Magnetic Resonance Imaging In First-Episode, Drug-Na(i|¨)ve Somatization Disorder

Objective:Neuroimaging studies have provided evidences of brain structural and functional alterations in patients with somatization disorder (SD). Most of the altered brain regions are belonged to the default mode network (DMN). These findings highlight the importance of brain mechanism in SD. However, few studies applied resting-state functional magnetic resonance imaging (rs-fMRI) to explore the pathophysiology of SD. The present study was designed to investigate the (1) regional alterations of the DMN, (2) changes of voxel-wise functional networks, (3) changes of interhemispheric FC in SD patients using rs-fMRI.Methods:1. Twenty-five first-episode, medication-naive patients with SD were recruited and diagnosed according to the Structured Clinical Interview of the DSM-IV (SCID), and 28 age-, sex-, education-matched healthy controls (HC) were recruited from the community in the same period. All subjects underwent a rs-fMRI scan.2. All subjects were evaluated by the Hamilton depression scale (HAMD), the Hamilton anxiety scale (HAMA) and the somatization subscale of the Symptom Check List 90 (SCL-90) at the scan day.3. After image data preprocessing, the fractional amplitude of low-frequency fluctuations (fALFF), graph theoretical approach and voxel-mirrored homotopic connectivity (VMHC) were applied to analyze the resulting data.4. Whole-brain voxel-based correlation analyses were used to identify the fALFF, FCS, VMHC values in regions with significant group differences and age, education, illness duration, the scores of HAMD、HAMA、somatization subscale of SCL-90.5. The split-half and leave-one-out validations were used to examine the reproducibility of the results of VMHC.Results:1. The scores of HAMD, HAMA and somatization subscale scores of SCL-90 in SD patients group are 18.84±7.31,22.96±10.95,28.48±10.37, respectively. Compared with healthy control, patients with SD showed higher levels of depression, anxiety and somatic symptoms (p< 0.001).2. Patients with SD showed increased fALFF in the bilateral superior medial prefrontal cortex (MPFC) and decreased fALFF in the left precuneus (PCu) using fALFF method. MPFC locates in anterior regions of the DMN and PCu locates in the posterior regions of the DMN, suggesting a dissociation pattern between the anterior and posterior parts of DMN in SD. Furthermore, significantly positive correlation was observed between the z values of the voxels within the bilateral superior MPFC and somatization subscale scores of the Symptom Check List (SCL-90) in patients with SD.3. Compared to HC, patients with SD showed significantly increased functional connectivity strength (FCS) in the right inferior temporal gyrus (ITG) using graph theoretical approach. There is a significant positive correlation between the z values of the cluster in the right ITG and HAMA scores.4. In comparison with HC, patients had lower VMHC in the angular gyrus and insula using VMHC method. The reproducibility of the results was validated using the split-half and leave-one-out validations.Conclusions:1. MPFC, PCu, right inferior temporal gyrus, angular gyrus and insula are abnormal in SD patients, and these abnormal regions may be important brain regions for the pathophysiology of SD.2. The results provide evidences of the importance of the DMN in the pathophysiology of SD.3. The abnormity of MPFC and right inferior temporal gyrus are positively correlated with the severity of somatization symptoms and anxiety symptoms respectively, suggesting that the fALFF value of MPFC and FCS value of right inferior temporal gyrus may be applied as an indicator for the severity of somatization symptoms and anxiety symptoms, respectively.