SNCA and Parkinson disease: Multiple studies have investigated cerebrospinal fluid (CSF) biomarkers in PD motor subtypes; CSF Aβ-42 and P-tau181 concentrations have associated with the PIGD but not with TD or intermediate phenotypes [25], while CSF α-synuclein levels were found to be significantly lower in non-TD or PIGD phenotypes compared with the TD phenotype [26, 27].