Cerebral amyloid angiopathy-related inflammation and amyloid-related imaging abnormalities: Common magnetic resonance imaging findings and shared diagnostic clues – A narrative review

Abstract

Cerebral amyloid angiopathy-related inflammation (CAA-ri) is a clinical and neuroradiological manifestation reported in CAA patients as autoimmune encephalopathy. Its pathomechanisms are still incompletely understood, and its similarities with amyloid-related imaging abnormalities (ARIA) described in clinical trials of immunotherapy for Alzheimer’s disease (AD) emerged in recent literature. If CAA-ri is a spontaneous event, ARIA may occur either spontaneously or after immunization. The diagnostic criteria of both these inflammatory manifestations, mainly based on neuroimaging findings, are partially different. A better understanding of the underlying mechanisms could lead to a common shared definition and criteria. Indeed, the coexistence of CAA and AD is a frequent occurrence, and the interpretation of neuroimaging findings must take account of it. In this review, the main neuroimaging findings of CAA-ri on magnetic resonance imaging are addressed with a minor focus on the chronic small vessel disease hallmarks. The main aim of this review is to show that ARIA is a name for a neuroradiological pattern (derived from AD immunization trials) that is spontaneously present in patients with cerebral amyloid angiopathy within a clinical–neuroradiological disorder known as CAA-ri in both parenchymal and leptomeningeal involvement.