MRI Characteristics In Patients With Two Types Of Mild Cognitive Impairment

Mild cognitive impairment (MCI) is a descriptive category that identifiespatients with memory impairment beyond that expected for age and education,who do not qualify for a diagnosis of dementia. The term MCI has becomewidely used, with the suggestion that it is a prodromal state of Alzheimer’sdisease (AD) and possibly other dementias. MCI has been classified broadly intoamnestic and nonamnestic subtypes. Emerging MR techniques such as DTI andproton density imaging and advancements in image analysis software packagesprovide us an efficient tool for early detection of subtle brain microstructural,perfusion and metabolic changes.1. White matter changes in amnestic MCI detected by diffusion tensorimagingObjective: To use DTI, by measuring fractional anisotropy (FA) and meandiffusivity (MD), to test1) if Higher significantly FA reduction in aMCI group;2) if Higher significantly MD increased in aMCI group;3) The structuresinvolved in the aMCI. Methods: DTI were preformed on40patients with aMCI,and28normal control subjects. Fractional anisotropy (FA) and mean diffusivity(MD) based tract-based spatial statistics (TBSS) analyses in each individual andgroup comparisons were carried out. Results: Compared to NC, aMCI patientsshowed significant FA reduction bilaterally, in frontal, parietal, and temporallobes, corpus callosum, association fibers, projection fibers, bilateral coronaradiation, right posterior thalamic radiation and right sagittal stratum. aMCIpatients also showed significantly increased MD widespreadly in frontal,parietal and temporal lobes, corpus callosum, associate fibers and projection fibers. Conclusion: Assessment of frontal lobe WM; parietal lobe WM;temporal lobe WM; corpus callosum and cingulum by diffusion tensor imagingmay aid early diagnosis of aMCI. 2. Structural and Functional Changes in Subcortical Vascular MildCognitive Impairment: a Combined Voxel-based Morphometry andResting-State Functional MRI studyObjective: Subcortical vascular mild cognitive impairment (svMCI) hasbeen presented as the earliest stage of cognitive decline which was associatedwith vascular disease. Methods: We revealed gray matter volume changes withstructural magnetic resonance imaging (sMRI) and spontaneous low frequencyfluctuations (LFF) with resting-state functional MRI (rs-fMRI) in11svMCI and22normal controls. Gray matter volume and low-frequency fluctuation mapswere calculated and between-group comparisons were conducted with multipleregression analyses. Results: Compared to normal controls, svMCI patientsshowed significant gray matter volume reductions in the inferior frontal gyrus,inferior parietal lobule, anterior cingulated cortex, insula and superior temporalgyrus. Significant decreases in the amplitude of low-frequency fluctuations(ALFF) were identified in the posterior cingulate cortex, precuneus, temporalgyrus and inferior parietal lobule in svMCI. The ALFF in svMCI wassignificantly increased in several other brain regions, including the occipital lobe and cerebellum. These group differences in ALFF remained after adjusting forstructural differences between the two groups. Conclusion: This pilot study inChinese subjects confirms previous findings that svMCI is associated withstructural and functional abnormalities in multiple brain regions. Further studiesin this area will help to highlight the pathophysiology of svMCI and vasculardementia.