SNCA and Parkinson disease: Braak α-synuclein stage (p = 0.01), Thal amyloid-β (Aβ) phase (p = 0.001), Braak NFT stage (p = 0.003) and CERAD neuritic plaque score (p < 0.001) were all higher in PDD compared to PD patients (Figure 1 and Supplementary Table 2).