TBSS-Based Study On White Matter Damage In Amnestic Mild Cognitive Impairment And Alzheimer's Disease

BackgroundAlzheimer's disease(AD),a neurodegenerative disease with insidious onset,is the most common type of dementia in old age.The incidence rate and prevalence of AD are closely related to age.With the aging of China's population,the number of AD patients surges,which is bound to increase the burden of patients' family and social public medical and health services,and will seriously hinder our country' s economic development.At present,the pathogenesis of AD is still unclear.Recently,the therapeutic drugs developed according to the relevant pathogenesis have failed successively in the clinical stage,and the existing drugs can only delay rather than reverse the course of AD.Therefore,the current treatment strategy for AD is gradually shifting to early diagnosis and intervention.Mild cognitive impairment(MCI)is a state between normal aging and mild dementia.As a type with high AD conversion rate,amnestic mild cognitive impairment(aMCI)is closely related to AD.The study of aMCI is of great significance for the early diagnosis of AD.Hippocampal volume measurement has been recognized as one of the most valuable methods for the diagnosis of AD,but conclusions of researches in MCI patients about it vary widely.More and more researches suggest that white matter of brain changes in the early stage of AD,even earlier than gray matter.Based on the above research background,this study aims to explore the significance of hippocampal volume measurement and white matter changes in the early diagnosis of AD.Purpose:To explore the significance of hippocampal volume measurement and the brain white matter study based on Tract-Based Spatial Statistics in the early diagnosis of AD.Methods:10 patients of aMCI and 22 patients of AD who visited the department of neurology of The First Affiliated Hospital of Zhengzhou University from January to December of 2018 were continuously selected,and 25 healthy volunteers in the same period were selected as the control group.All subjects underwent relevant neuropsychological scale tests,hippocampal volume measurement,3.0T MRI diffusion tensor imaging(DTI)scanning,the DTI anisotropic fraction(FA)graphs of the three groups were pretreated,and the FA values in the whole brain of the three groups were statistically analyzed with TBSS to calculate the fibers with statistical differences.The relationship between standardized hippocampal volume,FA value of statistically different fibers and neuropsychological scale score was analyzed.Results:1.There was no significant difference in MMSE and DST between the aMCI group and the control group(P > 0.05),while there were significant differences in MoCA,AVLT-immediate,AVLT-5min,AVLT-20 min,BNT,CDT and TMTA(P < 0.05).There were significant differences in MMSE,MoCA,AVLT-immediate,AVLT-5min,AVLT-20 min,BNT,CDT,DST,TMTA between AD group and control group(P < 0.05).There was significant difference in MMSE between aMCI group and AD group(P < 0.05).while there was no significant difference in MoCA,AVLT-immediate,AVLT-5min,AVLT-20 min,BNT,CDT,DST,TMTA(P > 0.05).2.Compared with the control group,the aMCI group showed a decrease in left hippocampal volume,and the difference was statistically significant(P < 0.05),while there was no significant difference in the total hippocampal volume and the right hippocampal volume(P > 0.05)Compared with the control group,the total hippocampal volume,left hippocampal volume and right hippocampal volume of the AD group all decreased,and the differences were statistically significant(P < 0.05).Compared with AD group,aMCI group showed no significant difference in total hippocampal volume,left hippocampal volume and right hippocampal volume(P > 0.05).3.Correlation analysis between hippocampal volume and cognitive score:The total hippocampal volume was positively correlated with MMSE,MoCA,AVLT-immediate,AVLT-5min,AVLT-20 min,BNT,CDT,DST,and negatively correlated with TMTA(P < 0.05).The left hippocampal volume was positively correlated with MMSE,MoCA,AVLT-5min,AVLT-20 min,BNT,CDT,DST,and negatively correlated with TMTA(P < 0.05).The right hippocampal volume was positively correlated with MMSE,MoCA,AVLT-5min,AVLT-20 min,BNT and DST(P < 0.05),but not with CDT and TMTA(P > 0.05).4.The FA values in genu of corpus callosum,body of corpus callosum,splenium of corpus callosum,right cerebral peduncle,right posterior limb of internal capsule,bilateral anterior corona radiata,bilateral superior corona radiata,bilateral posterior corona radiata,bilateral posterior thalamic radiation(include optic radiation),right external capsule,right cingulum(cingulate gyrus),right fornix/stria terminalis,bilateral superior longitudinal fasciculus were significantly lower in aMCI group than in control group.(P<0.05).The FA values in middle cerebellar peduncle,genu of corpus callosum,body of corpus callosum,splenium of corpus callosum,fornix(column and body of fornix),left corticospinal tract,bilateral cerebral peduncle,bilateral internal capsule,bilateral anterior corona radiata,superior corona radiata,posterior corona radiata,bilateral posterior thalamic radiation(include optic radiation),bilateral sagittal stratum(include inferior longitudinal fasciculus and inferior frontal occipital fasciculus),bilateral external capsule,bilateral cingulum(cingulate gyrus),bilateral fornix/stria terminalis,bilateral superior longitudinal fasciculus,bilateral uncinate fasciculus were significantly lower in AD group than in control group.(P<0.05).There is no significant difference of FA value between AD group and aMCI group.5.In the aMCI group,MoCA scores had a positive correlation with decreased FA values of genu of corpus callosum,body of corpus callosum,right cerebral peduncle,right anterior corona radiata,bilateral posterior corona radiata,right fornix/stria terminalis;AVLT-immediate scores had a positive correlation with decreased FA values of left anterior corona radiata;AVLT-5min scores had a positive correlation with decreased FA values of left superior corona radiata;TMTA scores had a negative correlation with decreased FA values of right posterior limb of internal capsule,bilateral posterior corona radiata;DST scores had a positive correlation with decreased FA values of right fornix/stria terminalis.(P<0.05)In the AD group,AVLT-20 min scores had a negative correlation with decreased FA values of middle cerebellar peduncle;BNT cores had a positive correlation with decreased FA values of right superior corona radiata,right uncinate fasciculus;CDT scores had a negative correlation with decreased FA values of middle cerebellar peduncle,fornix,right cingulum(cingulate gyrus);TMTA scores had a negative correlation with decreased FA values of left cingulum(cingulate gyrus),bilateral uncinate fasciculus;DST scores had a positive correlation with decreased FA values of right anterior limb of internal capsule.Conclusions:1.Hippocampal volume atrophy has occurred in aMCI patients,and the reduction of left hippocampal volume may be of certain significance for the early diagnosis of AD.2.Patients with aMCI and AD have extensive white matter damage,but the specificity of the damage site is not high.White matter damage of cingulum(cingulate gyrus),fornix/stria terminalis,superior longitudinal fasciculus,corpus callosum,optic radiation may have certain significance for the early diagnosis of AD.The inferior longitudinal fasciculus,inferior frontal occipital fasciculus,uncinate fasciculus and cerebellar white matter fiber may be involved only after the development of AD to a certain extent.