SNCA and Parkinson disease: Using histological techniques based on the discovery that Lewy bodies and neurites are strongly stained by antibodies to alpha-synuclein, Braak et al.25 developed a new staging system suggesting that PD first appears in the brainstem (dorsal motor nucleus of the vagus nerve, Braak Stage I), then spreads rostrally over time to the pons and mesencephalon, causing cell loss in the locus ceruleus (Stage II) and substantia nigra (Stage III), until it eventually involves the basal forebrain and the cerebral cortex (Stage VI).