NRGN and Alzheimer disease: We tested the specific hypotheses that the CSF Ng levels were altered in patients with AD and had diagnostic utility for AD, that the CSF Ng correlated with AD core biomarkers (CSF Aβ, phosphorylated tau (p-tau) and total tau (t-tau)), cognitive decline and imaging evidence of neurodegeneration and that the CSF Ng levels predicted future cognitive impairment at the early asymptomatic stage.