Microbleed topography, leukoaraiosis, and cognition in probable Alzheimer disease from the Sunnybrook Dementia Study

Background: Microbleeds are hemosiderin deposits around small vessels and are well visualized with T2*-weighted gradient-recalled echo (GRE) imaging. Objectives: To determine frequency and topography of microbleeds in Alzheimer disease (AD) and to assess their association with leukoaraiosis and cognition. Design: Case-control cross-sectional analysis. Microbleeds were counted using GRE imaging. Leukoaraiosis was rated on T2-weighted and proton density -weighted scans using the Age-Related White Matter Changes Rating Scale (ARWMC). Neuropsychological tests indexed cognition. Setting: The Cognitive Neurology Clinic, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada. Patients: Individuals with probable AD (n= 80) and healthy controls (n= 25) from a longitudinal cohort with GRE sequences as part of standard imaging protocol (2002-2006). Results: Microbleeds occurred in 29% of patients with AD and 12% of controls and were multiple (> 1) in 48% of patients with AD and 33% of controls. There was lobar (vs centrencephalic) predominance in 92% of AD patients, with occipital lobes accounting for 57% of these microbleeds. The ARWMC scores (P <. 005) were significantly higher in AD patients with microbleeds than in those without, and microbleeds correlated with total (r= 0.39, P=. 01) and parietooccipital (r= 0.28, P <. 01) ARWMC scores. We were unable to demonstrate an association between microbleeds (or leukoaraiosis) and cognitive performance. Conclusions: Occipital predominance of microbleeds with corresponding parietooccipital leukoaraiosis has not been well described in prior imaging studies of AD. Microbleeds were frequent, often multiple, and predicted greater leukoaraiosis. These findings illustrate the complexity of AD vasculopathy and the need for additional studies in dementia and stroke populations.