White Matter Microstructure And Connectivity In Crohn’s Disease:A Preliminary Study

Crohn’s disease(CD)is an inflammatory bowel disease,and can affect any part of the gastrointestinal tract.The major symptoms of disease include abdominal pain,diarrhoea,weight loss,fatigue and fever.In Europe and North America,approximately one in every 300 adults is affected by CD and CD has an increased incidence.Many factors,such as genetic,environmental,and dysfunctional immune systems,can play a role in the development of the disease.However,the pathogenesis of the disease still requires further research.In recent years,neuroimaging studies have found brain structural and functional abnormalities in CD patients,such as gray matter volume changes of the amygdala implicated in psychological disturbances,and thalamus associated with pain and CD,but study of white matter in CD is still lacking.In current thesis,multimodal magnetic resonance imaging data of CD patients and healthy controls(HCs)were used to study the abnormalities of white matter microstructure and connectivity between two groups.Firstly,we studied the alterations of white matter microstructure and tracts connectivity in CD patients.The result of white matter microstructure revealed that contrast to HCs,CD patients had decreased fractional anisotropy(FA),increased mean diffusivity and radial diffusivity in genu of corpus callosum,body of corpus callosum,left superior corona radiata,left superior longitudinal fasciculus,left posterior thalamic radiation,and right anterior corona radiation(significant difference disappeared with anxiety and depression as covariates).The result of connectivity in white matter tracts reported that contrast to HCs,CD patients had aberrant connectivity pattern between the genu of corpus callosum and right anterior limb of internal capsule,as well as between the body of corpus callosum and left middle cingulate cortex.The result of correlation exhibited that CD patients had negative correlations between the disease duration and FA values of body of corpus callosum/right anterior limb of internal capsule,as well as between the disease severity and FA values of right external capsule.These investigation findings suggest that abnormalities of white matter microstructure and tracts connectivity may increase our understanding of the white matter in CD.Secondly,we detected the changes of the amygdala functional connectivity between the CD patients and HCs,and between CD patients with high anxiety/depression scores and other patients.Compared to HCs,CD patients displayed decreased functional connectivity of the left amygdala with bilateral insula,right parahippocampus and right anterior middle cingulate cortex/dorsal anterior cingulate cortex,and decreased functional connectivity of the right amygdala with right parahippocampus and bilateral anterior middle cingulate cortex/dorsal anterior cingulate cortex.Compared to other patients,CD patients with high anxiety/depression scores showed increased functional connectivity of the left amygdala with left thalamus and left orbitofrontal cortex,and increased functional connectivity of right amygdala with left thalamus.These findings indicate that decreased functional connectivity of the amygdala may be related to decreased inhibitory control on processing of visceral sensory and pain in CD patients,and increased functional connectivity of the amygdala may be associated with high sensitivity to negative emotion.Thirdly,we examined the difference in grey matter structure and structural connectivity of the thalamic subregions among CD patients with and without abdominal pain and HCs.In contrast to CD patients without abdominal pain and HCs,CD patients with abdominal pain exhibited decreased grey matter density in bilateral prefrontal and right temporal thalamic subregions.In contrast to HCs,CD patients with abdominal pain had decreased structural connectivity between the right prefrontal thalamic subregion and left medial prefrontal cortex.This current finding reveals that structural connectivity change between the prefrontal thalamic subregion and medial prefrontal cortex may involve in abnormalities of visceral sensory processing.The present study provide the preliminary evidence for white matter microstructure and connectivity changes.We hope that these investigations could enhance understanding of pathogenesis of CD.