NEFL and Alzheimer disease: Besides the core AD biomarkers CSF Aβ42, Aβ40, p-tau181 and total tau, the markers include α-synuclein as a gauge of synaptic dysfunction; S100b, YKL-40 and glial fibrillary acidic protein (GFAP) [97] as markers of astrocyte activation; soluble TREM2 and IL-6 as markers of microglial activation and inflammation [98]; and neurofilament light (NfL) and neurogranin [99] as markers of axonal injury and synaptic dysfunction.