Cerebral Amyloid Angiopathy

Cerebral amyloid angiopathy (CAA) is characterized by the accumulation of amyloid beta-peptides (A beta) in the walls of leptomeningeal arteries, arterioles, and veins. Despite the fact that these pathological changes were first described in 1909, major advancement in our understanding of the clinicoradiological manifestations, neurobiology, and course of CAA has occurred only during the last 30 years. No significant associations have been shown between CAA and other systemic/visceral amyloidoses or vascular risk factors, including hypertension. CAA is well known as the most common cause of spontaneous and anticoagulant-related lobar parenchymal ICH in the elderly. It also causes lobar cerebral microbleeds (CMBs), small dot-like dark susceptibility artifacts visible with gradient recalled echo (GRE)-magnetic resonance imaging (MRI). CMBs are important markers of disease severity and predictors of CAA progression. Amyloid angiopathy is also a common cause of ischemic microvascular white matter disease (WMD) and deep cerebral infarctions. Such WMD is defined as subcortical and periventricular white matter changes without obvious infarction, as well as a dark appearance on computerized tomography (CT) and a bright appearance on fluid attenuated inversion recovery (FLAIR)-MRI. CAA-related vascular dysfunction, with its hemorrhagic and ischemic complications, is a recognized contributor to vascular cognitive impairment in the elderly, an independent effect that is synergistically increased by Alzheimer pathologies, such as plaques and tangles. A set of clinicoradiological criteria was established for the accurate diagnosis of CAA. According to the Boston Criteria, patients aged 55 years and older with multiple hemorrhages (on CT or GRE-MRI) restricted to the lobar, cortical, or corticosubcortical regions (cerebellar hemorrhage allowed) are diagnosed as probable CAA when no other etiology is found; a single hemorrhage in the same region is classified as possible CAA. Current guidelines recommend that patients with non-valvular atrial fibrillation suspected to have CAA-related ICH not be offered long-term anticoagulation therapy because of the significant risk of rebleeding.