The aim of this study is to investigate longitudinal differences in Ng, BACE1 and Ng/BACE1 cerebrospinal fluid (CSF) levels in predementia Alzheimer’s disease patients as a prequel to drug trials stratified for putative subgroups with increased susceptibility to associated Alzheimer’s disease mechanisms. This evidence concerns the gene NRGN and early-onset autosomal dominant Alzheimer disease.