SNCA and multiple system atrophy: MSA is distinguished into two major disease subtypes, largely based on the predominant clinical symptoms underlined by different vulnerable sites of synuclein pathology and neurodegeneration: (1) the Parkinsonian variant (MSA-P), with predominant striatonigral degeneration (SND), and (2) the cerebellar variant (MSA-C), with olivopontocerebellar atrophy (OPCA) [161,162,163].