The Pathophysiologic Basis of Secondary Narcolepsy and Hypersomnia

• Published in: Current neurology and neuroscience reports Vol. 11; no. 2; pp. 235 - 241
• Main Authors: Kanbayashi, Takashi, Sagawa, Yohei, Takemura, Fumi, Ito, Sachiko-Uemura, Tsutsui, Ko, Hishikawa, Yasuo, Nishino, Seiji
• Format: Journal Article
• Language: English
• Published: New York Current Science Inc 01.04.2011; Springer Nature B.V
• Subjects: Adolescent; Brain cancer; Cerebrospinal fluid; Child; Disorders of Excessive Somnolence - pathology; Disorders of Excessive Somnolence - physiopathology; Encephalitis; Head injuries; Humans; Hypothalamus; Hypothalamus - metabolism; Hypothalamus - pathology; Hypotheses; Intracellular Signaling Peptides and Proteins - metabolism; Ligands; Magnetic Resonance Imaging; Male; Medicine; Medicine & Public Health; Middle Aged; Multiple sclerosis; Narcolepsy - etiology; Narcolepsy - pathology; Narcolepsy - physiopathology; Neurology; Neuromyelitis Optica - immunology; Neuromyelitis Optica - pathology; Neuromyelitis Optica - physiopathology; Neuropeptides - metabolism; Neurosciences; Orexins; Sleep disorders; Trauma; Vein & artery diseases; Japan; NMO; EDS; MS; CSF; Narcolepsy; Hypocretin; Orexin; REM sleep; Cataplexy
• ISSN: 1528-4042; 1534-6293
• DOI: 10.1007/s11910-011-0178-y

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.