The CSF levels of FL-Ng significantly correlated positively with all synaptic markers CT-Ng (rho = 0.595, P = 0.003), synaptotagmin, 215–223 (rho = 0.577, P = 0.004), and synaptotagmin, 238–245 (rho = 0.585, P = 0.003) [6, 7], except from SNAP-25 in AD patients (Table 3). Here, NRGN is linked to Alzheimer disease.