| Objective: To explore possible mechanism of the hippocampal abnormality inpatients with relapsing-remitting multiple sclerosis (RRMS) by analyzing change infunctional connectivity between hippocampus and the whole brain, regionalfunctional connectivity and structure with the use of technology including restingstate functional connectivity (RSFC), regional homogeneity(ReHo) and diffusiontensor imaging fiber tractography (DTI-FT),and analyzing correlation between thechange mentioned before and cognitive function.Methods:24cases of RRMS patients clinically diagnosed and24healthyvolunteers with sex, age and education level matched were performed by3.0T MRIbrain scan to acquire conventional image and functional data including blood oxygenlevel dependent signal and diffusion tensor imaging. Data analysis include:(1)Resting state fMRI data pre-processing was performed by resting state dataprocessing assistant based on MATLAB platform. Bilateral hippocampus wereextracted as ROIs by using REST software to proceed the whole functionalconnectivity. ReHo method was used to calculate regional functional connectivityinside hippocampus.(2) Diffusion Toolkit software and Track Vis software wereapplied to extract the DTI parameters (ADC value, FA values) of bilateralhippocampus. All subjects underwent clinical rating scale (EDSS, PASAT, MFIS).The general condition, the clinical score and DTI parameters (ADC value, FAvalues)in hippocampus between RRMS group and the healthy controls (HCs) were analyzedwith SPSS software for two-sample t test, then RSFC and ReHo value by using SPM8software. Clinical rating scale, RSFC abnormal area, ReHo abnormal area,and DTIparameters in RRMS group were proceeded for Pearson correlation analysisrespectively.Results:(1) MFIS score (t=11.7, P=0.001) and EDSS score in RRMS group were higher than HCs, PASAT score lower than HCs(t=3.449, P=0.001).(2) In RRMS group, the left hippocampus as ROI showed decreased functionalconnectivity with left parahippocampal gyrus(brodmann area36,BA36),increasedfunctional connectivity with left rear side cerebellar,right middle frontal gyrus (BA9),right inferior frontal gyrus(BA47) and right supramarginal gyrus(BA40).We alsofound that the right hippocampus as ROI showed increased functional connectivitywith left rear side cerebellar.(3) Compared with HCs, ReHo value in the cranial and caudal parts of lefthippocampus was decreased(P <0.05, AlphaSim correction, voxel>10).(4) Compared with HCs, left hippocampus of RRMS patients showedsignificantly increased ADC(t=3.147, P=0.004) and decreased FA(t=3.544, P=0.001). ADC values were negatively significantly correlated with FA values in eachlateral hippocampus of RRMS patients.(5)Brain regions which have abnormal functional connectivity with the lefthippocampus include right frontal gyrus which has correlation with clinical scorePASAT score (r=0.473, P=0.019), left hippocampus ADC values (r=-0.502, P=0.012) and FA values (r=0.477, P=0.019). The right supramarginal gyrus hasnegative correlation with the left hippocampus ADC values (r=-0.506, P=0.012).Left hippocampus ADC values (r=-0.481, P=0.017), FA values (r=0.438, P=0.032) have negative, positive correlation with PASAT scores respectively.Conclusions:(1) There was abnormality of functional connectivity betweenhippocampus and whole brain as well as inside hippocampus in patients with RRMS,which has correlation with cognitive function.(2) RRMS patients presented structural abnormalities in hippocampus, the leftcerebral hemisphere lateralization and correlation between the left hippocampalstructual damage and cognitive function.(3)Structural change in the left hippocampus and abnormal functionalconnectivity of left hippocampus including right middle frontal gyrus and supramarginal gyrus presented the correlation. The structural change affectedfunctional connectivity of hippocampus, thereby affecting patients with normalcognitive function, which may be one of the mechanisms of cognitive function inRRMS patients. |
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