White Matter Changes In Mild Cognitive Impairment: A Diffusion Tensor Imaging Study

Background:Mild cognitive impairment(MCI) is recognized as an intermediate clinical cognitive impairment stage between the normal aging and dementia,which has a high risk to develop into dementia.MCI has been considered as the best stage for early diagnosis' and intervention of AD.Structural magnetic resonance imaging(MRI) studies on mild cognitive impairment(MCI) and Alzheimer's disease(AD) have largely focused on the brain's cortical gray matter.Although pathoanatomical and imaging studies have confirmed both microscopic and macroscopic white matter changes(WMC) in patients with AD and MCI,controversy exists regarding the relevance of WMC,the pathogenic mechanisms producing WMC,and the association of WMC with cognitive dysfunction.Diffusion tensor imaging(DTI) is a novel and unique technique that is able to show the brain white matters and their orientation in vivo.Recently developed voxel-based analysis is based on the highly automatic computer technology.It does not need hypothesis of brain regions variation,can rule out the subjective error of operator and thus represent a comprehensively objective assessment for whole brain DTI variation.It can evaluate the changes of brain white matter in MCI patient more precisely.Objectives:To measure microstructural differences in the brains of participants with amnestic mild cognitive impairment(aMCI) compared with control group using an magnetic resonance diffusion tensor imaging(DTI) technique with voxel-based analysis.Methods:A standardized clinical and neuropsychological evaluation was conducted on each subject.31 participants(15 participants with aMCI,16 healthy elderly adults) underwent magnetic resonance imaging(MRI)-based DTI.To control for the effects of anatomical variation,diffusion images of all participants were registered to standard anatomical space.Voxel-by-voxel comparisons showed significant regional reductions of FA in participants with aMCI compared to controls in white matter regions.Results:Significantly decreased FA values measurements(p＜0.001) were observed in the right frontal white matter in participants with aMCI.Moreover, there was a statistically significant difference between aMCI and controls considering the small regions of bilateral superior frontal gyrus white matter (p＜0.001).Conclusions:White matter damage of frontal lobe may play an important role in histopathologic changes associated with amnestic mild cognitive impairment.