title: The pathophysiologic basis of secondary narcolepsy and hypersomnia.
abstract: The symptoms of narcolepsy can occur during the course of other neurologic conditions (ie, symptomatic narcolepsy). Inherited disorders, tumors, and head trauma were the three most frequent causes for symptomatic narcolepsy. Other causes include multiple sclerosis (MS), vascular disorders, and encephalitis. Cerebrospinal fluid hypocretin-1 measures were carried out in some recent cases with symptomatic narcolepsy, and moderate decreases in hypocretin levels were seen in a large majority of these cases. Excessive daytime sleepiness (EDS) in these symptomatic cases was sometimes reversible with an improvement of the causative neurologic disorder and with an improvement of the hypocretin (orexin) status. Recently, we found that several symptomatic narcoleptic cases with MS show unique bilateral symmetric hypothalamic lesions associated with significant hypocretin ligand deficiency. In addition, these patients often share the clinical characteristics of neuromyelitis optica (NMO) and the detection of NMO-IgG (or anti-aquaporin-4 [AQP4] antibodies), suggesting a new clinical entity. Further studies of the involvement of the hypocretin system in symptomatic narcolepsy and EDS are helpful to understand the pathophysiologic mechanisms for occurrence of EDS and cataplexy.
authors.affiliation: Department of Neuropsychiatry, Akita University School of Medicine, Akita, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Kanbayashi
authors.forename: Yohei
authors.initials: Y
authors.lastname: Sagawa
authors.forename: Fumi
authors.initials: F
authors.lastname: Takemura
authors.forename: Sachiko-Uemura
authors.initials: SU
authors.lastname: Ito
authors.forename: Ko
authors.initials: K
authors.lastname: Tsutsui
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Hishikawa
authors.forename: Seiji
authors.initials: S
authors.lastname: Nishino
mesh_terms: D000293:Adolescent; D002648:Child; D006970:Disorders of Excessive Somnolence / Q000473:pathology / Q000503:physiopathology*; D006801:Humans; D007031:Hypothalamus / Q000378:metabolism / Q000473:pathology; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009290:Narcolepsy / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology*; D009471:Neuromyelitis Optica / Q000276:immunology / Q000473:pathology / Q000503:physiopathology; D009479:Neuropeptides / Q000378:metabolism; D000068797:Orexins
chemical_list: C000596229:HCRT protein, human; D047908:Intracellular Signaling Peptides and Proteins; D009479:Neuropeptides; D000068797:Orexins