van Veluw SJ, et al. - Researchers intended to understand how the severity of cerebral amyloid angiopathy (CAA) and microbleeds and microinfarcts are related to each other and to the events that produce formation of lesions. Intact formalin-fixed hemispheres of 12 CAA cases were scanned with MRI, accompanied by a histopathological examination of pre-defined areas and serial sectioning of targeted multiple lesion areas. No significant correlation was noted between number of microbleeds and microinfarcts with increasing CAA severity. The density of Aβ positive cortical vessels was lower surrounding a microbleed vs a simulated control lesion and higher surrounding microinfarcts. While Aβ was often seen upstream or downstream (71%), as was extensive fibrin(ogen) build-up (87%), serial sectioning showed that for microbleeds both Aβ and smooth muscle cells were virtually never present in the vessel wall at the site of bleeding. Conversely, few vessels associated with microinfarcts had intact smooth muscle cells (9%), while vascular Aβ was almost always seen at the core of the lesion as well as upstream or downstream (82%).