[Excessive daytime sleepiness and low CSF orexin-A/hypocretin-I levels in a patient with probable progressive supranuclear palsy].

We report a 74-year-old woman with excessive daytime sleepiness (EDS) who were diagnosed as probable progressive supranuclear palsy (PSP). Her EDS mimicked narcolepsy without cataplexy, because multiple sleep latency tests showed short latencies, human leukocyte antigen testing was positive for DR2/DQB1, and orexin A (hypocretin-I) concentration in her cerebrospinal fluid was undetectable. In PSP, neurofibrillary tangles appears in the hypothalamus, neuronal loss and gliosis are seen in a number of pontine and mesencephalic tegmental nuclei, substantia nigra, locus caeruleus. These neuropathological changes of PSP may cause decreased pre- or post-synaptic hypothalamic orexin neurotransmission because orexin neurons are located in the hypothalamus and project widely to the forebrain and the brain stem. In our patient, the treatment with methylphenidate HCl was effective on EDS.