SNCA and Classical progressive supranuclear palsy: α-syn: α-synuclein; CBS: corticobasal syndrome; CSF: cerebrospinal fluid; DAergic: dopaminergic; FDG: fluoro-deoxy-glucose; IHC: immunohistochemistry; IHF: immunohistofluorescence; MIBG: metaiodbenzylguanidin; MRI: magnetic resonance imaging; MSA: multiple system atrophy; MSA: multiple system atrophy; PD: Parkinson’s disease; PD: Parkinson’s disease; PET: positron emission tomography; PSP: progressive supranuclear palsy; PSP: progressive supranuclear palsy; SAA: seeding amplification assay; SPECT: single-photon emission computerized tomography