Study Of CSTC Circuit In Obsessive-compulsive Disorder Using DTI And MRS

Obsessive-compulsive disorder(OCD)is a mental disorder with relatively high prevalence rate with limited therapeutic strategies.Various studies have shown that abnormalities in the cortico-striato-thalamo-cortical(CSTC)circuit are closely related to the OCD pathophysiology,but the underlying structural and metabolic mechanisms remain unclear.This study utilized a combined diffusion tensor imaging(DTI)and magnetic resonance spectroscopy(MRS)methodology to investigate the co-occurrence of structural and metabolic changes in OCD patients aimed to provide a more comprehensive view of OCD pathological mechanism.Specfically,we investigated the dorsal anterior cingulate cortex(dACC),bilateral thalamus and anterior thalamic radiation(ATR)area of CSTC circuit.We also studied the correlation between fractional anisotropy(FA)and Yale-Brown ObsessiveCompulsive Scale(Y-BOCS)scores,including Y-BOCS compulsion and obsession scores,to examine the clinical relevance of the extracted neuroimaging biomarkers in OCD pathophysiology.In the multi-modal study on dACC area,we used MRS to obtain the concentration information of important metabolites and analyzed the FA of regional white matter area using ROI-based DTI analysis.The group difference of concentration and structural parameter,as well as their correlation were investigated.We also analyzed the relationship between FA and clinical scores.The results showed that choline(Cho)concentration of dACC in OCD patients was positively correlated with FA(r = 0.530,p = 0.042).The FA of dACC in OCD patients was positively correlated with Y-BOCS total score(r = 0.540,p = 0.038)and Y-BOCS compulsion score(r = 0.667,p = 0.007).These results further illustrated the importance of dACC in the pathophysiology of OCD.In the multi-modal study of bilateral thalamus metabolism and anterior thalamic radiation(ATR)structure of OCD,we used MRS to quantify the concentration of important metabolites in the bilateral thalamus.Diffusion tensor fiber tracing method was applied to reconstruct bilateral ATR as well as obtain structural parameters,including FA,volume,length and number of fibers.These parameters were then compared between OCD and health control groups,and pearson correlation analysis was conducted between metabolic concentrations and structural parameters.We found that the mean fiber length of right ATR negatively correlated with ipsilateral thalamic choline level in OCD patients(r =-0.768,p = 0.002).In addition,significantly higher Cho concentration was detected in right thalamus of OCD patients compared to healthy controls(p = 0.038).The mean FA value of right ATR correlated with patients Y-BOCS total score(r = 0.413,p = 0.036),as well as Y-BOCS compulsion score(r = 0.430,p = 0.028).These results suggested that the coupling feature between right thalamic metabolism and ATR structure was closely linked to the pathogenesis of OCD.