A Diffusion Tensor Imaging Study Of Brain White Matter Structure In Patients With Non-neuropsychiatric Systemic Lupus Erythematosus

Neuropsychiatric systemic lupus erythematosus(NPSLE)is a complication of systemic lupus erythematosus(SLE)when the disease involves to the central and peripheral nervous system.In the early stage of NPSLE,patients without neuropsychiatric symptoms have been referred to as non-NPSLE patients.In recent years,studies found that brain structural and functional abnormalities have already appeared in non-NPSLE patients' brain,and the impairments of white matter in the brain were considered as a relatively important factor.Diffusion tensor imaging(DTI)is a radiological technology that could noninvasively access the direction of nerve fibers and the information of the fiber myelin.In the present study,we applied two kinds of analysis methods that are based on DTI technology to investigate the differences of white matter structure between non-NPSLE patients and healthy controls(HCs).In the first research part,the micro-structure of white matter was analyzed by the tract-based spatial statistics(TBSS)method which is based on DTI technology.The experiment acquired the images of 29 non-NPSLE female patients and 29 female HCs who were selected after the inclusion criteria and exclusion criteria.After the standard processing steps of TBSS in FSL software,the fractional anisotropy(FA)skeleton map of each subject was calculated,and the statistical analysis of whole brain significant differences between groups on FA skeleton maps was carried out.The results of this study showed that the FA value in several regions of non-NPSLE brains was significant decreased comparing with the HCs.These regions mainly included the body of corpus callosum,splenium of corpus callosum,genu of corpus callosum,bilateral anterior corona radiata,bilateral superior longitudinal fasciculus,bilateral superior corona radiata and posterior thalamic radiation et al.The results suggested that the integrity of white matter in non-NPSLE group was decreased,the micro-structure of myelin and axons may be abnormal.In the second research part,we employed the network analysis method that is based on DTI technology to study the white matter structural network.By using probabilistic tractography and the graph theory analysis methods,we investigated the abnormalities of white matter connectivity across the whole brain and network topological properties in non-NPSLE patients.The basic processes of brain network analyses are:data preprocessing;segment the brain into 90 functional regions on the basis of the standard AAL template;reconstruct the white matter fibers by probabilistic tractography and construct the structural network matrix;calculate several topological measures of the networks;statistical analyses.The results of the research were:(1)The non-NPLE patients presented significant reduced global and local network efficiencies but showed increased characteristic path length,reflecting impaired capacity of information integration and exchange in patients' networks;(2)The brain hub distribution identified by the nodal degree metric was changed in the non-NPSLE patient group;(3)The nodal efficiency of non-NPSLE group was significant decreased in the right opercular and triangular parts of the inferior frontal gyrus,the left median cingulate and paracingulate gyri,the nodal degree of patient group was significant decreased in the right inferior frontal gyrus,bilateral median cingulate and paracingulate gyri,right fusiform gyrus,and right precuneus but significant increased in the left superior frontal gyrus and the left inferior occipitalgyrus,these regions with significantly altered nodal properties were mainly involved in language,visual,and DMN systems;(4)The global,local network efficiencies and nodal properties of several abnormal regions in patients' network were negatively correlated with the disease activity index;(5)The patients exhibited a subnetwork of significant decreased connectivity and a subnetwork of significant increased connectivity.In the present study,two parts of investigations that are based on DTI technology found that the integrity of partial white matter fibers was decreased in non-NPSLE patients,and the topological properties of white matter connectivity networks in non-NPSLE patients were significantly differ from healthy controls'.The findings in this study provide imaging basis for further investigation of the pathogenesis in the early stage of NPSLE.