NRGN and Alzheimer disease: Our data of higher CSF Ng concentrations in patients with AD are in agreement with previous reports [8, 9, 50–54], as well as with a meta-analysis comparing CSF Ng levels in patients with AD and other neurodegenerative diseases including FTLD [55], highlighting the connection with AD-specific pathophysiological processes that appear to be markedly different from those driving FTLD in the context of markers of postsynaptic dysfunction.