Defining the neuropathological background of vascular and mixed dementia and comparison with magnetic resonance imaging findings

The concept of vascular dementia (VaD) has greatly evolved in the past decades. Advances in neuroimaging techniques have led to a better identification of cases with small vessel disease and chronic ischemic changes. Autopsy data from population-based studies have revealed the frequent occurrence of both vascular and degenerative lesions in aged brains. However, the clinical significance of vascular pathology has been difficult to establish. This chapter will review data from clinicoradiological and clinicopathological studies that have attempted to define the cognitive impact of macroscopic and microscopic ischemic pathology in pure VaD and in cases with associated degenerative pathology. Magnetic resonance imaging studies have focused on lacunes and white matter lesions, whereas autopsy series have provide important insights into the clinical correlates of macroinfarcts,lacunes, diffuse and periventricular demyelination, microinfarcts and focal and diffuse gliosis.Results from these studies have led to a better understanding of the influence of lesion type,location and severity on cognitive function. Vascular scores have been proposed that can be combined with well-established classifications of Alzheimer's disease (AD) pathology to distinguish mixed dementias from pure AD and pure VaD.