Schelle J, Wegenast-Braun BM, Fritschi SK, et al. - Since the causal role of Aβ for cerebral amyloid angiopathy (CAA) and associated hemorrhages was not disputed, so researchers assessed the benefits of Aβ reduction at early disease time points in order to prevent CAA in the absence of parenchymal amyloid. For visualizing CAA and assessing Aβ in CSF and the brain, 3D-ultramicroscopy and immunoassays were used. This is the first study demonstrating that when parenchymal amyloid is lacking, lowering Aβ at early illness time points mostly prevents CAA. Beginning at the onset of CAA and continuing for 4 months, BACE1 inhibitor treatment showed a 90% Aβ reduction in CSF and basically prevented CAA progression and related pathologies. The observation offers a preclinical foundation for Aβ-reducing therapies in patients with CAA risk and presymptomatic HCHWA-D.