NEFL and peripheral neuropathy: Additionally, in line with previous studies (Gaiottino et al., 2013; Lu et al., 2015; Benatar et al., 2018; Feneberg et al., 2018; Verde et al., 2019; Ashton et al., 2021), we demonstrated a strong association between cNfL and pNfL, and showed that pNfL also provides a robust diagnostic marker for ALS, especially after excluding patients with peripheral neuropathy, a condition associated with a higher increase of NfL values in plasma than in CSF (Bischof et al., 2018; Mariotto et al., 2018; Sandelius et al., 2018).