 The primary objectives are to characterize at baseline and 2-year follow-up in patients with significant Periventricular White Matter Hyperintensities pvWMH, presenting as transient cerebrovascular events or memory problems, patterns of: 1. Uptake of amyloid on Florbetapir F-18 PETCT 2. Glucose uptake on 18F-FDG PETCT 3. Volumetric measures of brain structure on MRI imaging 4. Performance on standard neuropsychological assessments, activities of daily living and gait speed. 