Although we did not find significant differences in CSF Ng concentrations between MCI and mild AD, as previously reported [35], probably because of the small sample, Aβ42/Ng was found to be higher in MCI than moderate AD, and the same was true for the Aβ 42/40 ratio, while we found no difference for α-Syn and Aβ 42/α-Syn. This evidence concerns the gene NRGN and Alzheimer disease.