NEFL and Parkinson disease: Evidence indicates the potential diagnostic and prognostic merit of cerebrospinal fluid (CSF) and blood biomarkers authentically mirroring the pathogenesis of PD, such as α-synuclein isoforms, lysosomal enzymes, amyloid and tau pathology markers, and neurofilament light chain (NFL) (Parnetti et al., 2019; Bouthour et al., 2019; Ashton et al., 2020).