Rosengren et al. (1996) were the first to show the potential of NFL as biomarker for ALS: in 1996, they developed a new ELISA assay for NFL and found that the protein was present at higher concentrations in the CSF of 12 ALS patients compared with 34 neurologically healthy individuals. Several years later, increased NFL levels in the CSF of ALS patients were reported also in comparison with other neurological, including neurodegenerative, diseases (Zetterberg et al., 2007; Tortelli et al., 2012). Here, NEFL is linked to amyotrophic lateral sclerosis.