Here we reported the results of a comprehensive evaluation of the diagnostic and prognostic value of NfL and α-syn seeding activity, including the comparison between cNfL and pNfL performance, and the analysis of the added value of a combined CSF analysis of NfL and α-syn seeding activity, in a large cohort of patients with parkinsonism and related prodromal syndromes. Here, NEFL is linked to Parkinson disease.