Obsessive-compulsive Disorder Resting State Function And Structural Magnetic Resonance Study

Objective:Obsessive-compulsive disorder(OCD)is a common mental disorder with the lifetime prevalence of 2%-3%in the general population.OCD is characterised by recurrent obsessions(concerns involving contamination,harm,or sexual and religious preoccupations)or compulsions(e.g.,washing,checking,repeating,ordering,counting),or both,that cause clinically significant distress or impairment in social,occupational,or other important areas of functioning.The pathophysiology of OCD is not yet fully understood,however over the last few years,evidence for abnormalities of fronto cortico-striatal-thalamic circuitry(CSTC loop)has accumulated,Magnetic Resonance Imaging technology had been used to investigate the further sub-circuitries formatted the recent model of OCD pathophysiology from structural and functional areas.Methods:Patients were admitted from the outpatients in Nanjing Brain Hospital Affiliated to Nanjing Medical University during October 2011 to October 2015,and healthy control subjects were recruited during the same time.The Yale-Brown Obsessive Compulsive Scale(Y-BOCS),Hamilton Rating Scale for Depression 17-Item(HAMD-17)and Hamilton Anxiety Rating Scale(HAMA)were used to assess the clinical symptoms.All of the participants were scanned with magnetic resonance imaging(MRI)and were analysised by using SPM8,VBM8,DPARSF,REST and FSL software tools.Independent-samples T test was used to compare the changes of ACC-based functional connectivity and whole brain VMHC values between the OCD patients and the healthy controls.The differences of the FA values measured from the whole brain DTI between the two groups were analyzed based on tract based spatial statistics(TBSS).FA data were statistically compared between the two groups based on nonparametric random permutation test(RPT).Pearson's correlation analysis,partial correlation analysis or linear regression analysis was used to analysis the relationship between the changes of structure or function.Results:1)All of the 70 OCD patients were separated to four dimensions:unacceptable mind 26(37.14%),checking18(25.71%),washing17(24.29%),ordering7(10%),mix2(2.86%).2)As compared with the controls,The weaker functional connectivity to ACC in OCD patients than the control included areas of left inferior frontal gyrus,right supplementary motor area;while stronger connectivity were in areas of right hippocampus,right insula and right fusiform gyrus.And significant postive correlations between functional connectivity strength from left inferior frontal gyrus to ACC and total Y-BOCs(r=0.351,p=0.017).5)Compared with the control,untreated OCD patients showed higher VMHC in orbitofrontal cortex(OFC);lower VMHC in thalamus and putamen;significant postive correlations between VMHC in orbitofrontal cortex(OFC)and total Y-BOCs(r=-0.296,p=0.017).3)As compared with the controls,the untreated unacceptable/taboo thoughts subtype OCD had a significantly lower FA in the corpus callosum;right superior longitudinal fasciculus;right posterior thalamic radiation(optic radiation);right inferior fronto-occipital fasciculus.We did not find any significant correlation between FA values and the clinical symptom scores.Conclusion:1)The pathophysiology models of OCD are cortex-striatal-thalamus-cortex(CSTC)circuitry and some other areas beyond the CSTC circuitry.2)Functional connection abnormality of OCD is not confined to cortical-subcortical loop,and mirrored homotopic functional connectivity also shows a certain abnormality.3)The abnormality of the white matter microstructure may be the structural basis of the pathologic physiological mechanism of the OCD patient.