SNCA and Parkinson disease: Similarly, others have reported decreased levels of α-synuclein, raised levels of o-α-syn and increased o-α-syn/total α-synuclein ratio in the CSF of PD patients compared to that in age-matched control subjects or various non-PD neurological controls (Tokuda et al., 2010; Hansson et al., 2014; Park et al., 2011; Parnetti et al., 2014a,b; van Steenoven et al., 2018).