SNCA and Parkinson disease: Nonetheless, studies showed that some PD cases cannot be staged by the Braak staging system, as some patients presented with evident LB pathology first in the locus coeruleus, SNpc, and the amygdala, and then in the dorsal motor nucleus of the vagus (DMV) and gut, representing a rostro-caudal route of α-synuclein transmission from the CNS to the ENS [9].