HCRT and Parkinson disease: Other clinical studies have also investigated orexin levels using either plasma, spinal CSF or ventricular CSF in alpha-synucleinopathies such as PD [29, 30], MSA [52, 53], and DLB [31, 54], and even in the prodromal stage of alpha-synucleinopathies such as RBD [55, 56].