For example, synaptosomal-associated protein-25 kDa (SNAP-25) [8, 18, 20] and synaptotagmin I [29, 30], were increased in CSF even at the earliest preclinical stages [31] and more recently, synaptic vesicle glycoprotein 2A (SV2A) has been proposed as a promising PET imaging target to assess decreased synaptic density in AD patients [32, 33]. Here, SNAP25 is linked to Alzheimer disease.