Recently, synaptic vesicle glycoprotein 2A (SV2A), a 12-transmembrane glycoprotein found in synaptic vesicles of neurons, has emerged as a promising PET imaging target for assessing synaptic density in neurodegenerative conditions, including Alzheimer disease, ischemic stroke (18–21), and traumatic brain injury (22). Here, SV2A is linked to early-onset autosomal dominant Alzheimer disease.