NEFL and multiple system atrophy: This study was therefore designed to 1) confirm our findings of NfL in CSF as diagnostic marker of early MSA using a different, high-sensitivity platform; 2) assess NfL in the plasma of the same patients using the same assay platform, compare values in plasma with those in CSF, and assess NfL-p as diagnostic marker; and 3) assess for change of NfL in both CSF and plasma over time starting at an early disease stage, and explore if the change in NfL or NfL at baseline are associated with or predict clinical disease progression.