P2‐208: Cortical thinning in early‐stage and late‐stage amnestic mild cognitive impairment

Abstract

Amnestic mild cognitive impairment (aMCI) represents a pre-dementia stage of Alzheimer's disease (AD). According to the severity of objective memory impairment, aMCI patients can be classified into subjects with milder degree of impairment and those with more severe impairment. Although previous studies showed that aMCI subjects with milder memory impairment have slower rates of AD progression than those with more severe memory impairment, there has been no study comparing regional cortical thickness according to this classification of aMCI. Cortical thickness across the entire brain and neuropsychological performance were measured in 271 patients with aMCI and 234 subjects with normal cognition (NC). According to the performances in delayed recall items of memory tests, aMCI patients were divided into early-stage aMCI (EMCI, N = 91) with milder degree of memory impairment (scores between -1.5 SD and -1.0 SD compared to age-, sex-, and education-matched norms) and late-stage MCI (LMCI, N = 180) with more severe memory impairment (lower than -1.5 SD). We performed ANCOVAs to compare neuropsychological performances and vertex-wise cortical thinning in EMCI, LMCI, and NC. Compared to NC subjects, EMCI patients showed cortical thinning in the left medial temporal lobe, and LMCI patients showed cortical thinning in bilateral medial temporal lobes, bilateral medial and lateral parietal cortices, bilateral dorsolateral prefrontal cortices, right posterior cingulate cortex, and bilateral anterior temporal cortices. When the two aMCI groups were directly compared, LMCI patients showed more cortical thinning in the right medial temporal lobe, right posterior cingulate cortex, right lateral parietal cortex, and right dorsolateral prefrontal cortex. Both EMCI and LMCI patients showed lower performances in all neuropsychological tests compared to NC. When directly compared with EMCI, LMCI subjects had poorer performance in all memory tests and COWAT supermarket test, while having comparable scores in other tests.