NRGN and Alzheimer disease: Since synapse degeneration occurs in all neurodegenerative processes, it is an unexpected finding that CSF neurogranin concentrations are not increased in other neurodegenerative disorders such as Parkinson’s disease, frontotemporal dementia, Lewy body dementia, progressive supranuclear palsy, or multiple system atrophy, indicating that high CSF neurogranin might be specific for Alzheimer’s disease [14, 15•].