SNAP25 and Alzheimer disease: Moreover, cerebrospinal fluid SNAP 25 is a newly discovered marker of synaptic damage, and its increase indicates that patients with early AD (i.e., AD-induced SCI) have an elevated ratio of CSF SNAP25 and SNAP25 to Aβ42, while the ratio of CSF SNAP25 and SNAP25 to Aβ42 is very sensitive for the diagnosis of AD.