Topographical distribution of A beta predicts progression to dementia in A beta positive mild cognitive impairment

IntroductionAbnormal brain amyloid beta (A beta) 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 A beta pathology can provide additional information to identify, among global A beta positive individuals, those destined for dementia. MethodsWe studied 260 amnestic mild cognitive impairment (MCI) subjects who were A beta-PET positive with [F-18]florbetapir. Using [F-18]florbetapir, we assessed the percentage of voxels sowing A beta abnormality as well as the standardized uptake value ratio (SUVR) values across brain regions. Regressions tested the predictive effect of A beta on progression to dementia over 2 years. ResultsNeither global nor regional [F-18]florbetapir SUVR concentrations predicted progression to dementia. In contrast, the spatial extent of A beta pathology in regions comprising the default mode network was highly associated with the development of dementia over 2 years. DiscussionThese results highlight that the regional distribution of A beta abnormality may provide important complementary information at an individual level regarding the likelihood of A beta positive MCI to progress to dementia.