MRI Structural And Functional Study In Patients With AMCI And Mild Alzheimer's Disease

PARTⅠVoxel-Based MRI Analysis of Whole Brain Gray Matter in Patients withaMCI and mild Alzheimer's DiseaseObjective To study the pattern of volume changes of the whole braingray matter in patients with amnestic mild cognitive impairment(aMCI) and mildAlzheimer's disease (AD) by voxel-based morphometry (VBM). Material andMethods 33 patients with aMCI, 32 patients with mild AD and 31 normal agingvolunteers as control subjects were enrolled in the study. Gray matter volumedifferences of the whole brain were assessed using SPM5-based DARTEL toolbox tomake voxel-based morphometric comparison between patients and the control group.Results The volume of the left hippocampus,parahippocampal gyrus,lingualgyrus,superior temporal gyrus, bilateral insulae, middle temporal gyri,etc in the aMCIpatient group was significantly smaller than that in the control group (P＜0.05, FDRcorrected,K≥50 voxels). The volume of the bilateral hippocampi, parahippocampalgyri, amygdalae,thalami,temporo-occipital gyri,inferior parietal lobules,superiorparietal lobules,precuneuses,middle frontal gyri,and left cuneus,fusiform gyrus, rightposterior cngulate gyrus,inferior frontal gyrus,etc in the mild AD patients group wassignificantly smaller than that in the control group(P＜0.05,FDR corrected P＜0.05,FDR corrected,K≥50 voxels). Conclusion VBM can reveal widespreadvolumetric reduction of gray matter's fine structure in early-stage Alzheimer's diseasewith the advantage of objectivity. PARTⅡWhite Matter Abnormalities in Patients with aMCI and mildAlzheimer's Disease investigated with Voxel-Vased Diffusion Tensor ImagingObjective To detect white matter abnormalities in patients with amnesticmild cognitive impairment(aMCI) and mild Alzheimer's disease (AD) by voxel-basedDTI analysis. Material and Methods 33 patients with aMCI,32 patients with mild ADand 31 normal aging volunteers as control subjects were enrolled in the study.Fractional anisotropy (FA) maps were preprocessed using SPM5 to make voxel-wisecomparison of anisotropy in whole brain between patients and the control group.Results Significant reductions in FA values were found in the white matter of inferioroccipital gyrus,anterior part of cingulum,lingual gyrus,fusiform gyrus,inferior parietallobule in the left side and the white matter adjacent to the triangular part of the rightlateral ventricle and the white matter in bilateral frontal and temporal lobes in patientswith aMCI(P＜0.001,uncorrected, K≥20 voxels). In patients with mild AD, significantreductions in FA values were found in the corpus callosum,bilateral anterior part ofcingulum and the white matter of bilateral frontal lobes,temporal lobes,occipitallobes,inferior parietal lobules,right precuneus and cuneus and the white matter adjacentto bilateral hippocampi, the triangular part of the bilateral lateral ventricle and the rightcalcarine sulcus(P＜0.001,uncorrected, K≥20 voxels). Most of the areas with reducedFA values were not consistent with those with reduced gray matter volume in patientswith aMCI.While some of the areas with reduced FA values were in concordance withthose with reduced gray matter volume in patients with mild AD.ConclusionVoxel-wise comparison of anisotropy in whole brain between patients and the controlgroup can reveal widespread reduction of white matter anisotropy in aMCI and mildAlzheimer's disease with the advantage of objectivity.The fact that the pattern ofanisotropic changes of white matter was not in concordance with that of volumetricreduction of gray matter reveals that white matter anisotropic changes may be outcomefrom a couple of factors rather than wallerian degeneration solely. PARTⅢResting-State Functional MRI Analysis in aMCI and mild Alzheimer'sDiseaseObjective To investigate the brain activity in resting-state of patientswith aMCI and mild Alzheimer's disease by GroupICA. Material and Methods 33patients with aMCI,32 patients with mild AD and 31 normal aging volunteers ascontrol subjects were scanned with 3.0T MRI.fMRI data were preprocessed with suchsoftwares as SPM5,REST,GIFT and then compared between patients and the controlgroup. Results GroupICA detected 8 resting-state networks which act for differentfunctions.The spatial map of Default mode network(DMN) of aging volunteersrevealed by ROI-based correlation analysis was similar with that found by GroupICAwhich includes bilateral PCC,precuneus,cuneus,inferior parietal lobules,dorsomedialprefrontal cortices(DMPFC),dorsolateral prefrontal cortices(DLPFC),part of temporaland occipital Iobes(P＜0.05, FWER, K≥10 voxels).In addition, the DMN revealed byGroupICA also includes bilateral thalami,hippocampi,parahippocampi,insulae,whichindicate that ICA can reveal more areas than ROI-based correlationanalysis(P＜0.05,FWER, K≥10 voxels). GroupICA found that most areas of DMN haddecreased BOLD signal while increased BOLD signal were found in such areas asbilateral precuneus,cuneus,the middle part of cingulate gyri, putamina, striatumes andfight inferior parietal lobule(P＜0.05,FWER, K≥10 voxels).Increased activity werealso revealed in visual network(BA 18, 19) in patients with aMCI (P＜0.001,uncorrected,K≥10 voxels).These areas may provide compensation for the malfunction of memorysystem.GroupICA found areas with decreased activity in 2 lateralized networks withincreased activity in fight middle frontal gyrus (BA10,46) in patients with mildAD(P＜0.05,FWER, K≥10voxels).Both of the 2 lateralized networks play an importantrole in memory and attention function.Among all the areas of DMN found byGroupICA,only few areas such as left hippocampus presented gray matter atrophy aswell as decreased resting-state activity in the aMCI group.All the other areasmanifested decreased resting-state activity before the gray matter atrophy waspresented.The result of partⅡprovided the evidence that the damage of structuralconnectivity might be the physical foundation in the impairment of functionalconnectivity.Conclusion GroupICA can detect the abnormalities of resting-state brain activity before the structural altemation can be demonstrated.The combination ofstructural and functional analysis of the brain can reveal much more information thaneach of them solely, which is an important direction for future research.