Prevalence and pathogenic role of cerebrovascular lesions in Alzheimer disease

Cerebrovascular lesions in Alzheimer disease (AD) being significantly more frequent than in nondemented elderly subjects suggest overlaps and synergistic effects between both pathologies. Examination of a consecutive series of autopsy-proven AD cases and age-matched controls revealed a higher frequency of vascular lesions and of cerebral amyloid angiopathy (CAA) in AD (57.34% vs. 33.2% and 94.1% vs. 33.3%, respectively). These and previous data on vascular pathology in Parkinson disease emphasize its importance in these disorders. A study comparing the frequency and extent of general CAA and capillary CAA (CapCAA) in the postmortem frontal cortex of cases with high and low Braak stages showed no correlation between general CAA and dementia, only a low one with other vascular lesions except for cerebral hemorrhages. However, it was higher in AD than in controls with vascular pathology. The severity of CapCAA not correlating with general CAA showed high correlation with AD pathology, suggesting different pathogenesis of both types of CAA. Its elucidation may have implications for new therapeutic strategies. Considering the variability of vascular pathology in both AD and aged brains, the mechanisms behind their interactions are largely unknown, and further studies are needed to clarify their impact on cognitive impairment.