SNCA and Parkinson disease: For instance, α-synuclein is increased in the dorsal motor nucleus of the vagus nerve, the locus ceruleus, and the substantia nigra during the early phase of PD and in the cerebral cortical areas of advanced PD, ultimately affecting motor skills and causing a decline in cognitive function [1,4,5] Kang and his colleagues, demonstrated that measures of Aβ1-42, T-tau (total tau), P-tau181(tau phosphorylated at threonine181), and α-synuclein in CSF have prognostic and diagnostic potential in early-stage of PD.