Juxtacortical Lesion Precedes Lobar Microbleed During Anti-amyloid β Immunotherapy

Amyloid-related imaging abnormalities (ARIAs), including edema/effusion (ARIA-E) and hemosiderin deposition (ARIA-H), are complications of anti-amyloid β (Aβ) monoclonal antibody therapy for Alzheimer's disease (AD). A Japanese woman in her 70s with mild cognitive impairment due to AD, confirmed by positive amyloid positron emission tomography, developed a new lobar cerebral microbleed (CMB) after participating in aducanumab clinical trials. Magnetic resonance imaging revealed juxtacortical white matter hyperintensities on fluid-attenuated inversion recovery, which were later resolved as a novel CMB. Juxtacortical white matter hyperintensities may precede ARIA-H and may suggest cerebral amyloid angiopathy-related changes during anti-Aβ therapy. Monitoring of these lesions is essential.