INTRODUCTION: Synaptic damage, axonal neurodegeneration, and neuroinflammation 
are common features in Alzheimer's disease (AD), frontotemporal dementia (FTD), 
and Creutzfeldt-Jakob disease (CJD).
METHODS: Unicentric cohort of 353 participants included healthy control (HC) 
subjects, AD continuum stages, genetic AD and FTD, and FTD and CJD. We measured 
cerebrospinal fluid neurofilament light (NF-L), neurogranin (Ng), 14-3-3, and 
YKL-40 proteins.
RESULTS: Biomarkers showed differences in HC subjects versus AD, FTD, and CJD. 
Disease groups differed between them except AD versus FTD for YKL-40. Only NF-L 
differed between all stages within the AD continuum. AD and FTD symptomatic 
mutation carriers presented differences with respect to HC subjects. Applying 
the AT(N) system, 96% subjects were positive for neurodegeneration if 14-3-3 was 
used, 94% if NF-L was used, 62% if Ng was used, and 53% if YKL-40 was used.
DISCUSSION: Biomarkers of synapse and neurodegeneration differentiate HC 
subjects from neurodegenerative dementias and between AD, FTD, and CJD. NF-L and 
14-3-3 performed similar to total tau when AT(N) system was applied.