Topographical distribution of Aß predicts progression to dementia in Aß positive mild cognitive impairment.

ABSTRACT

INTRODUCTION: Abnormal brain amyloid beta (Aß) is typically assessed in vivo using global concentrations from cerebrospinal fluid and positron emission tomography (PET). However, it is unknown whether the assessment of the topographical distribution of Aß pathology can provide additional information to identify, among global Aß positive individuals, those destined for dementia. METHODS: We studied 260 amnestic mild cognitive impairment (MCI) subjects who were Aß-PET positive with [18F]florbetapir. Using [18F]florbetapir, we assessed the percentage of voxels sowing Aß abnormality as well as the standardized uptake value ratio (SUVR) values across brain regions. Regressions tested the predictive effect of Aß on progression to dementia over 2 years. RESULTS: Neither global nor regional [18F]florbetapir SUVR concentrations predicted progression to dementia. In contrast, the spatial extent of Aß pathology in regions comprising the default mode network was highly associated with the development of dementia over 2 years. DISCUSSION: These results highlight that the regional distribution of Aß abnormality may provide important complementary information at an individual level regarding the likelihood of Aß positive MCI to progress to dementia.