国际上对于阿尔茨海默病（AD）的认识,已经从1984年国立神经病学与语言障碍、卒中和阿尔茨海默病及相关疾病协会[1]的AD痴呆诊断标准、2007年[2]、2010年[3]和2014年[4]国际工作组提出的前驱期AD（prodromal AD）、症状前AD、无症状AD,和2011年美国国立老化研究院和阿尔茨海默病协会提出的AD源性轻度认知障碍（mild cognitive impairment due to AD,MCI due to AD）[5]和临床前期AD[6],发展到了今天的临床前期AD的主观认知下降（subjective cognitive decline,SCD）[7]阶段.SCD概念,为我们今后在临床研究中能够正确筛选认知正常者提出了重要的警示;同时使我们认识到从认知正常到痴呆这一连续病程中,除了要经历MCI阶段,之前还可有SCD阶段,如果能够在SCD阶段正确识别AD,对于AD的早期防治意义重大.那么如何早期识别AD临床前期的SCD呢？
Amnestic mild cognitive impairment （aMCI） is a prodromal stage of Alzheimer＇s disease （AD）, and 75%-80% of aMCI patients finally develop AD. So, early identification of patients with aMCI or AD is of great significance for prevention and intervention. According to cross-sectional studies, it is known that the hippocampus, posterior cingulate cortex, and corpus callosum are key areas in studies based on structural MRI （sMRI）, functional MRI （fMRI）, and diffusion tensor imaging （DTI） respectively. Recently, longitudinal studies using each MRI modality have demonstrated that the neuroimaging abnormalities generally involve the posterior brain regions at the very beginning and then gradually affect the anterior areas during the progression of aMCI to AD. However, it is not known whether follow-up studies based on multi-modal neuroimaging techniques （e.g., sMRI, fMRI, and DTI） can help build effective MRI models that can be directly applied to the screening and diagnosis of aMCI and AD. Thus, in the future, large-scale multi-center follow-up studies are urgently needed, not only to build an MRI diagnostic model that can be used on a single person, but also to evaluate the variability and stability of the model in the general population. In this review, we present longitudinal studies using each MRI modality separately, and then discuss the future directions in this field.
