NEFL and Parkinson disease: A recently completed 5-year study by Brit Mollenhauer et al, under the auspices of the Parkinson’s Progression Markers Initiative (PPMI), reported elevated Nfl levels in the blood of patients with PD or high risk of PD compared to healthy control subjects, and that these NfL levels increased over time and positively correlated with exacerbated motor symptoms [19].