The aim of this study was to map the distributions of synaptic vesicle protein 2A (SV2A) and other synaptic proteins in the brain and the brain-derived extracellular vesicles (BDEVs) of AD patients, analyze their associations with Aβ, tau, and the apolipoprotein E (APOE) ε4 allele, and investigate the biological role of SV2A. Here, APOE is linked to Alzheimer disease.