Symptomatic narcolepsy, cataplexy and hypersomnia, and their implications in the hypothalamic hypocretin/orexin system.
ABSTRACT Human narcolepsy is a chronic sleep disorder affecting 1:2000 individuals. The disease is characterized by excessive daytime sleepiness, cataplexy and other abnormal manifestations of REM sleep, such as sleep paralysis and hypnagogic hallucinations. Recently, it was discovered that the pathophysiology of (idiopathic) narcolepsy-cataplexy is linked to hypocretin ligand deficiency in the brain and cerebrospinal fluid (CSF), as well as the positivity of the human leukocyte antigen (HLA) DR2/DQ6 (DQB1*0602). The symptoms of narcolepsy can also occur during the course of other neurological conditions (i.e. symptomatic narcolepsy). We define symptomatic narcolepsy as those cases that meet the International Sleep Disorders Narcolepsy Criteria, and which are also associated with a significant underlying neurological disorder that accounts for excessive daytime sleepiness (EDS) and temporal associations. To date, we have counted 116 symptomatic cases of narcolepsy reported in literature. As, several authors previously reported, inherited disorders (n=38), tumors (n=33), and head trauma (n=19) are the three most frequent causes for symptomatic narcolepsy. Of the 116 cases, 10 are associated with multiple sclerosis, one case of acute disseminated encephalomyelitis, and relatively rare cases were reported with vascular disorders (n=6), encephalitis (n=4) and degeneration (n=1), and hererodegenerative disorder (three cases in a family). EDS without cataplexy or any REM sleep abnormalities is also often associated with these neurological conditions, and defined as symptomatic cases of EDS. Although it is difficult to rule out the comorbidity of idiopathic narcolepsy in some cases, review of the literature reveals numerous unquestionable cases of symptomatic narcolepsy. These include cases with HLA negative and/or late onset, and cases in which the occurrences of the narcoleptic symptoms are parallel with the rise and fall of the causative disease. A review of these cases (especially those with brain tumors), illustrates a clear picture that the hypothalamus is most often involved. Several cases of symptomatic cataplexy (without EDS) were also reported and in contrast, these cases appear to be often associated with non-hypothalamic structures. CSF hypocretin-1 measurement were also carried out in a limited number of symptomatic cases of narcolepsy/EDS, including narcolepsy/EDS associated with tumors (n=5), head trauma (n=3), vascular disorders (n=5), encephalopathies (n=3), degeneration (n=30), demyelinating disorder (n=7), genetic/congenital disorders (n=11) and others (n=2). Reduced CSF hypocretin-1 levels were seen in most symptomatic narcolepsy cases of EDS with various etiologies and EDS in these cases is sometimes reversible with an improvement of the causative neurological disorder and an improvement of the hypocretin status. It is also noted that some symptomatic EDS cases (with Parkinson diseases and the thalamic infarction) appeared, but they are not linked with hypocretin ligand deficiency. In contrast to idiopathic narcolepsy cases, an occurrence of cataplexy is not tightly associated with hypocretin ligand deficiency in symptomatic cases. Since CSF hypocretin measures are still experimental, cases with sleep abnormalities/cataplexy are habitually selected for CSF hypocretin measures. Therefore, it is still not known whether all or a large majority of cases with low CSF hypocretin-1 levels with CNS interventions, exhibit EDS/cataplexy. It appears that further studies of the involvement of the hypocretin system in symptomatic narcolepsy and EDS are helpful to understand the pathophysiological mechanisms for the occurrence of EDS and cataplexy.
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ABSTRACT: Niemann-Pick disease type C (NPC) is an inherited lipid storage disorder, characterized by a defect in intracellular trafficking of exogenous cholesterol that leads to the lysosomal accumulation of unesterified cholesterol. We report a Japanese patient with NPC caused by a homozygous c.2974 G > T mutation of the NPC1 gene, which predicts a glycine (GGG) to tryptophan (TGG) change at codon 992 (designated as p.G992W). This is a well-known NPC1 gene mutation that causes a unique phenotype of NPC, which has been limited to a single Acadian ancestor in Nova Scotia, Canada. Our patient characteristically started presenting with cataplexy at the age of 9 years. Recent studies have shown reduced hypocretin-1 levels in the cerebrospinal fluid (CSF) of narcoleptic patients with cataplexy. In our patient, the level of hypocretin-1 was determined as moderately low, 174 pg/ml (normal, > 200 pg/ml). To date, CSF levels of hypocretin-1 have been determined by using an identical assay method in 7 cases of NPC, including our case. All of the NPC cases with cataplexy demonstrated low levels of CSF hypocretin-1, confirming the association of reduced CSF hypocretin-1 levels with cataplexy in NPC.The Tohoku Journal of Experimental Medicine 07/2006; 209(3):263-7. DOI:10.1620/tjem.209.263 · 1.28 Impact Factor
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ABSTRACT: The American Academy of Sleep Medicine (AASM) commissioned a Workgroup to develop quality measures for the care of patients with narcolepsy. Following a comprehensive literature search, 306 publications were found addressing quality care or metrics. Strength of association was graded between proposed processes or metrics and desired outcomes. Following the AASM process for quality metric development we identified three outcomes (including one outcome measure) and seven process measures. The first desired outcome was to reduce excessive daytime sleepiness by employing two process measures: quantifying sleepiness and initiating treatment. The second outcome was to improve the accuracy of diagnosis employing the two process measures: completing both a comprehensive sleep history and an objective sleep assessment. The third outcome was to reduce adverse events through three steps: ensuring treatment follow-up, documenting medical comorbidities, and documenting safety measures counseling. All narcolepsy measures described in this report were developed by the Narcolepsy Quality Measures Workgroup and approved by the AASM Quality Measures Task Force and the AASM Board of Directors. The AASM recommends the use of these metrics as part of quality improvement programs that will enhance the ability to improve care for patients with narcolepsy. © 2015 American Academy of Sleep Medicine.Journal of clinical sleep medicine: JCSM: official publication of the American Academy of Sleep Medicine 01/2015; DOI:10.5664/jcsm.4554 · 2.83 Impact Factor
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ABSTRACT: Sleep disorders are common in patients with multiple sclerosis (MS) and play a crucial role in health and quality of life; however, they are often overlooked. The most important sleep disorders in this context are as follows: insomnia, restless legs syndrome, periodic limb movement disorders, and sleep-related breathing disorders (SRBD). It is unclear if MS-related processes (lesions, brain atrophy) can cause symptomatic forms of sleep apnea. MS-related narcolepsy-like symptoms are described in the literature and, in some cases, have resolved with methylprednisolone pulse therapy. Similarly, REM sleep behavior disorder (RBD) is very rare in MS, but it can be an initial sign of MS where cortisone therapy may be helpful and can be taken into account in this specific context. Independent diagnosis and treatment is required for all of the abovementioned conditions. Treating physicians and neurologists should be aware of these comorbidities and initiate specific therapy. Highly fatigued or sleepy MS patients should have polysomnography in order not to overlook these diagnoses.Current Neurology and Neuroscience Reports 05/2015; 15(5):546. DOI:10.1007/s11910-015-0546-0 · 3.67 Impact Factor