It is not yet known whether the glymphatic dysfunction (i) is an early event in frontotemporal dementia, already detectable in presymptomatic disease stages; (ii) is associated with a specific FTLD proteinopathy or may represent a common pathway related to neurodegeneration; (iii) is a marker of disease severity; (iv) correlates with markers of neuronal dysfunction or axonal damage, such as plasma neurofilament light chain (NfL) or glial fibrillary acidic protein (GFAP)25,26; and/or (v) predicts disease progression over time. Here, NEFL is linked to frontotemporal dementia.