Cerebral amyloid angiopathy--a disease or age-related condition

Cerebral amyloid angiopathy is characterized by deposition of amyloid in the walls of leptomeninged and cerebral blood vessels. Its most common form, sporadic CAA that results from deposition of beta-amyloid peptide, which is the subject of this short review, is present in virtually all cases of Alzheimer disease and is also common among non-demented subjects where its prevalence increases with age. Stroke due to massive cerebral lobar hemorrhage is the main clinical presentation of CAA, but transient neurologic symptoms due to microhemorrhages may also occur. CAA is also a risk factor for cerebral infarction and there is increasing evidence that CAA contributes to cognitive impairment in the elderly, usually in association with white matter abnormalities on imaging. Although the definitive diagnosis of CAA is neuropathologic, reliable diagnosis can be reached clinically, based on the occurrence of strictly lobar hemorrhages, particularly in the cortico-subcortical area when using gradient-echo or T2*-weighted magnetic resonance imaging. Experimental studies have shown that the origin of the vascular amyloid is neuronal, and that age-related degenerative changes in the vessel walls prevent its clearance from the brain along perivascular spaces and promote Abeta aggregation and CAA formation. The entrapped Abeta aggregates are toxic to various vascular wall components, including smooth muscle cells, pericytes and endothelial cells, leading to their eventual destruction and predisposition of the vessel wall to rupture and hemorrhage. However, more research is necessary to decipher the mechanism of CAA formation and its relation to cognitive decline in the elderly.