Changes Of Brain Microstructures On DKI Among AD,MCI And Normal People

Objective: Alzheimer’s disease(AD),manifested by progressive cognitive impairment and behavioral abnormalities,is the main cause of neurodegenerative dementia.Mild cognitive impairment(MCI)refers to the stage that cognitive function is impaired but has not been enough to be diagnosed as dementia.This definition was first proposed in2011 by the National Institude on Aging-Alzheimer’s disease Assoxiation(NIA-AA),which significantly advanced the diagnostic time of AD.Currently,there is no effective treatment to improve AD.If the treatment can be carried out at the early stage of AD,considerable time and opportunities will be gained for better intervention,and it may even delay the progression of the disease to an irreversible state.It is very important to find appropriate biomarkers for early accurate detection,regular monitoring and early intervention in the clinical diagnosis and treatment of AD and MCI.Imaging biomarkers are always the first choice of clinicians because of their non-invasiveness,timeliness and economical efficiency.Diffusion kurtosis imaging(DKI),a new technology extended from Diffusion tensor imaging(DTI),can reflect the microstructure changes of tissues and cells more accurately and effectively,which fully considers the fact that water molecules diffuse in tissues with non-Gaussian distribution.Neuropsychological test are the essential part of clinical practice,which can reflect the severity of patients’ cognitive impairment,and routine magnetic resonance imaging(MRI)to observe the atrophy of hippocampus and parietal lobe is the most commonly used method to evaluate AD and MCI.Our study aims to explore the differences of DKI in AD,MCI and normal people,and to study their correlation with neuropsychological test results and hippocampal and parietal atrophy scores,so as to find possible new non-invasive biomarkers for AD.Methods: Twenty patients who were diagnosed with AD in the Second Hospital of Dalian Medical University from July 2020 to December 2020 were selected,including 4males and 16 females with an average age of 75.40±8.85.At the same time,21 patients diagnosed with amnestic MCI were included,consisting of 7 males and 14 females with an average age of 71.81±6.56.Twenty normal healthy controls were randomly selected,including 6 males and 14 females with an average age of 73.30±9.19.3.0T magnetic resonance machine was used to perform DKI of the patients in the three groups.Frontal lobe-white matter(WM),parietal lobe-WM,temporal lobe-WM,occipital lobe-WM,precuneus-WM,hippocampus,splenium of corpus callosum,genu of corpus callosum,posterior limb of internal capsule,caudate nucleus,corona radiate and centrum semiovale were manually drawn as the regions of interest(ROI),then the images were processed and the parameters were collected.The following scales were used for the test of neuropsychological state in patients of these three groups,including Mini-mental state examination(MMSE),Montreal cognitive assessment scale(Mo CA),Hasegawa dementia scale revised(HDSR),Clinical dementia rating(CDR),Digit span test(DST),Verbal fluency test(VFT),Frontal assessment battery(FAB),Trail making test A(TMTA),Rey auditory verbal learning test(RAVLT),Neuropsychiatric inventory-questionnaire(NPI-Q),Hamilton anxiety scale(HAMA),Hamilton depression scale(HAMD)and Activity of daily living scale(ADL).Medial temporal lobe atrophy scale(MTA scale)and Koedam scale were used to evaluate the atrophy of hippocampus and parietal lobe.Results were statistically processed with SPSS11.0software.Results: There are no significant differences in age,gender,degree of education and previous history(hypertension,diabetes,smoking)in AD group,MCI group and normal control group(P>0.05).The scores of all these neuropsychological tests had statistical significance in the three groups(P<0.05).The results of MTA score and Koedam score were statistically significant in AD group,MCI group and normal control group(P<0.05).The DKI parameters with statistically significant differences in the three groups are as follows,including frontal lobe MK,MD,parietal lobe MD,RD,occipital lobe MD,RD,temporal lobe FAK,MK,RK,FA,MD,RD,precuneus MK,AK,MD,DA,RD,hippocampus FAK,MK,AK,RK,MD,DA,RD,splenium of corpus callosum MK,MD,genu of corpus callosum MK,RK,MD,RD,posterior limb of internal capsule MK,MD,DA,caudate nucleus RK,DA,corona radiate MK,MD,and centrum semiovale FAK,MK,FA,MD,RD(P<0.05).The MD value and MK value of frontal lobe,parietal lobe,occipital lobe,temporal lobe,precuneus,hippocampus,splenium of corpus callosum,genu of corpus callosum,posterior limb of internal capsule,lenticular nucleus,corona radiate,centrum semiovale has varying degrees of correlation with neuropsychological test results(P < 0.05),and the latter is more relevant.MD and MK in hippocampus were correlated with MTA score,MD in parietal lobe was correlated with Koedam score,MD and MK in precuneus lobe were correlated with Koedam score.Conclusion: 1.DKI can detect the differences of brain microstructure between AD,MCI and normal people,and can also identify the changes of advanced neural structures related to the pathology of AD,such as temporal lobe,precuneus and hippocampus.Besides,it can compensate for the deficiency of conventional MRI,and is capable of finding the pathological changes in microstructure before the appearance of macroscopic atrophy.2.MD and MK are sensitive to evaluate the pathological changes of brain tissue in patients with cognitive impairment,and MK has a stronger correlation with neuropsychological test results,which can better reflect the severity of cognitive impairment.3.Hippocampus MK and precuneus MD are expected to be the most sensitive single parameter maps for the evaluation of AD and MCI.