Background and Objectives:To investigate the natural history and outcomes following treatment for spontaneous amyloid-related imaging abnormalities (ARIA)-like in cerebral amyloid angiopathy-related inflammation (CAA-ri).Methods:A multicenter, hospital-based, longitudinal, prospective observational study of inpatients meeting CAA-ri diagnostic criteria, recruited through the iCAβ International Network, in the period January 2013 - March 2017. A protocol for systematic data collection at first-ever presentation and at subsequent in-person visits, including T1-weighted, GRE-T2*, fluid-suppressed T2-weighted (FLAIR), and T1 post-gadolinium contrast-enhancement images aquired on 1.5T MRI, was employed at 3, 6, 12, 24-months follow-up. Centralized reads of MRI images were performed blinded to clinical, therapeutic, and time-points information. Main outcomes were survival, clinical and radiological recovery, intracerebral hemorrhage (ICH), and recurrence of CAA-ri.Results:The study enrolled 113 participants (10.6% definite, 71.7% probable, and 17.7% possible CAA-ri), mean age 72.9 years, 43.4% female, 37.1% APOEε4 carriers. 36.3% had a history of Alzheimer’s disease, 33.6% of ICH. A history of ICH, as well as the occurrence of new ICH at follow-up, was more common in patients with cortical superficial siderosis at baseline (52.6% vs 14.3%; p< 0.0001 and 19.3% vs 3.6%; p<0.009, respectively). After the first-ever presentation of CAA-ri, 70.3% (95% CI, 61.6-78.5) and 84.1% (95% CI, 76.2-90.6) clinically recovered within three and twelve months, followed by radiological recovery in 45.1% (95% CI, 36.4 - 54.8) and 77.4% (95% CI, 67.7 - 85.9), respectively. After clinicoradiological resolution of the first-ever episode, 38,3% (95% CI, 22.9 - 59.2) had at least one recurrence within the following 24 months. Recurrence was more likely if intravenous high dose corticosteroid pulse therapy was suddenly stopped compared to slow oral tapering-off (Hazard Ratio 4.68; 95% CI, 1.57-13.93; p=0.006).Discussion:These results from the largest longitudinal cohort registry of patients with CAA-ri support the transient and potentially relapsing inflammatory nature of the clinical-radiological acute manifestations of the disease and the effectiveness of slow oral tapering-off after intravenous corticosteroid pulse therapy in preventing recurrences. Our results highlight the importance of differential diagnosis for spontaneous ARIA-like events in Aβ-driven diseases, including treatment-related ARIA in Alzheimer’s disease patients exposed to immunotherapy drugs.
