SNCA and Parkinson disease: Braak staging of PD [29] describes the presence of α-synuclein aggregates in different brain regions, appearing in six stages, with pathology originating in the region of the olfactory bulb and/or dorsal motor nucleus of the vagus and spreading to nigrostriatal regions, and then on to hippocampal and cortical regions, coincident with the manifestation of pre-motor, motor, and cognitive/emotional symptoms, respectively.