Study on the microstructure of hippocampus and parahippocampal gyrus in patients with cognitive impairment by NODDI

LIU Ying; ZENG Hui

Abstract：Objective To investigatethe microstructure ofbilateral hippocampus and parahippocampus in amnesic mild cog-nitive impairment(aMCI)and Alzheimer's disease(AD)by using the sensitivity and specificity of neurite orientation dispersion and density imaging(NODDI),to provide more information for exploring the pathological mechanism of AD,and to explore the clinical value of NODDI technology.Methods According to the inclusion and exclusion criteria,17 aMCI patients,20 AD pa-tients,and 21 normal controls were recruited for NODDI scans,and MRIcro software was used to measure the neurite density in-dex(NDI),orientation dispersion index(ODI),and volume fractionoftheisotropic compartment(Viso)in the bilateral hippo-campus and parahippocampal gyrus of each group.The differences of each parameter among the three groups were compared by using single-factor analysis of variance.For the parameters with differences,spearman correlation was used to analyze the correla-tion between the different parameters and the Mini-Mental State Examination(MMSE)score and Montreal Cognitive Assessment(MoCA)score,and the correlation coefficient r was obtained.Results The NDI and ODI values of bilateral hippocampus and parahippocampal gyrus were decreased to varying degrees(P<0.05),and Viso values were increased to different degrees(P<0.05).But,only the Viso values of the bilateral hippocampus were significantly different between the aMCI groups andADgroups(P<0.001).Correlation analysis showed that NDI value and ODI value were positively correlated with MMSE score and MoCA score,while,Viso value was negatively correlated with MMSE score and MoCA score,and compared with other parameters,the correlation coefficient of Viso value was highest.Conclusion NODDI can well quantitatively analyze the changes in the micro-structure of the hippocampus and parahippocampal gyrus in patients with cognitive impairment at different stages,thereby con-firming that the hippocampus and the parahippocampal gyrus are equally important to the hippocampal memory system,provid-ing more data for exploring the pathological mechanism of AD.At the same time,NODDI has good clinical value for cognitive evaluation,especially,the Viso value of bilateral hippocampus,which may even become a reliable reference index.