Significant association of baseline CSF Ng levels and 18F-Fluorodeoxyglucose positron emission tomography (FDG-PET) was identified in subjects with CN (β = -0.06, P = 0.002), MCI (β = -0.04, P = 0.017) and AD (β = -0.15, P = 0.009). The gene discussed is NRGN; the disease is Alzheimer disease.