NEFL and neurodegenerative disease: Blood levels of NfL show promise as a marker of general neurodegeneration; plasma or serum NfL levels are altered and correlate with MMSE scores in dementia syndromes and other neurodegenerative diseases (Al Shweiki et al., 2019; Khalil et al., 2020; Mattsson, Andreasson, et al., 2017; Sugarman et al., 2020; Zetterberg, 2016).