SNCA and Cognitive impairment: This is consistent with a previous study which suggested that NfL appears to be better at predicting the development of dementia than mild cognitive impairment.36 When taken together our findings of NFLs ability to predict motor, cognitive and functional progression as well as death could potentially be explained by it predicting a more malignant progression reflecting the magnitude of alpha synuclein deposition and anatomical dysfunction present.37 38