Altered Clearance and Amyloid-Related Imaging Abnormalities.

Amyloid-related imaging abnormalities (ARIA) are parenchymal edema/effusion and hemorrhage that occur as side effects of immunotherapies targeting beta-amyloid for patients with Alzheimer's disease (AD). The mechanism of ARIA remains unclear but is thought to be due to loss of vascular integrity secondary to overwhelming perivascular clearance pathways, worsening of cerebral amyloid angiopathy (CAA), removal of amyloid from the vessel wall, and initiation of a local immune response. Further imaging and neuropathological studies may help further inform the mechanism of ARIA and its relationship to underlying AD and CAA pathology.