NEFL and Parkinson disease: The relation between NfL and motor performance has been studied in MS (Allali et al., 2020), Parkinson disease (Aamodt et al., 2021; Ye et al., 2021) and in motoneuron disease, using Expanded Disability Status Scale, Unified Parkinson’s Disease Rating Scale and ALS Functional Rating Scale-revised, respectively (Vacchiano et al., 2021).