HCRT and Parkinson disease: Since the first report by Drouot et al. (2003), who described decreased ventricular CSF orexin levels in PD patients, which were related with the severity of the disease, other authors have confirmed decreased CSF orexin in PD (Fronczek et al., 2007; Asai et al., 2009) and in other neurodegenerative parkinsonisms (Yasui et al., 2006), and the relation of CSF orexin with severity of PD (Asai et al., 2009), and with the presence of sleep attacks (Asai et al., 2009).