Pihlajamäki Maija, Jauhiainen Anne M, Soininen Hilkka
Department of Neurology, Kuopio University Hospital Kuopio, Finland.
Curr Alzheimer Res. 2009 Apr;6(2):179-85. doi: 10.2174/156720509787602898.
Mild cognitive impairment (MCI), and the amnestic subtype of MCI in particular, is the most recent concept used to describe the intermediary state between healthy aging and Alzheimer's disease (AD). It is hoped that research focusing on MCI would yield markers for early identification of individuals with prodromal AD at such a pre-dementia stage when potential disease modifying therapies would be most efficacious. Magnetic resonance imaging (MRI) combined with various data analysis methods provides tools to investigate alterations in brain structure and function in vivo. Structurally, MCI is characterized by atrophy of the medial temporal lobe (MTL) structures such as the hippocampus and entorhinal cortex, and the amount of atrophy in MCI is intermediate between healthy aging and AD. Additionally, atrophy of the posteromedial cortices such as the posterior cingulum and precuneus as well as of the lateral temporal cortices has been reported. The pattern of atrophy appears to vary according to the subtype of MCI. Functional MRI studies in MCI, compared to healthy aging and AD, have demonstrated both increased and decreased MTL activity during encoding novel visually presented material. Differences in the MTL activation pattern in MCI subjects may relate to differences in the severity of cognitive decline. There is some evidence that increased MTL activity observed during encoding may be compensatory due to incipient atrophy in the MTL structures. The resting state (or, "default mode") network, and the posteromedial cortical regions in particular, appear to malfunction in MCI. It is suggested that both altered MTL and posteromedial cortical function may be indicative of future cognitive decline from MCI to clinical AD.
轻度认知障碍（MCI），尤其是遗忘型MCI，是用于描述健康衰老与阿尔茨海默病（AD）之间中间状态的最新概念。人们希望，针对MCI的研究能够产生标志物，以便在痴呆前期（此时潜在的疾病修饰疗法可能最为有效）早期识别前驱AD患者。磁共振成像（MRI）结合各种数据分析方法，为在体研究脑结构和功能的改变提供了工具。在结构上，MCI的特征是内侧颞叶（MTL）结构（如海马体和内嗅皮质）萎缩，MCI的萎缩程度介于健康衰老和AD之间。此外，还报告了后内侧皮质（如后扣带回和楔前叶）以及外侧颞叶皮质的萎缩。萎缩模式似乎因MCI的亚型而异。与健康衰老和AD相比，MCI的功能MRI研究表明，在编码新呈现的视觉材料时，MTL活动既有增加也有减少。MCI受试者MTL激活模式的差异可能与认知衰退的严重程度差异有关。有一些证据表明，编码期间观察到的MTL活动增加可能是由于MTL结构的早期萎缩而产生的代偿作用。静息态（或“默认模式”）网络，尤其是后内侧皮质区域，在MCI中似乎存在功能障碍。有人认为，MTL和后内侧皮质功能的改变都可能预示着MCI未来向临床AD的认知衰退。
