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      A Practical Guide to the Therapy of Narcolepsy and Hypersomnia Syndromes

      review-article
      Neurotherapeutics
      Springer-Verlag
      Narcolepsy, Hypocretin, Orexin, Sodium oxybate, Modafinil, Venlafaxine

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          Summary

          Narcolepsy and other syndromes associated with excessive daytime sleepiness can be challenging to treat. New classifications now distinguish narcolepsy/hypocretin deficiency (also called type 1 narcolepsy), a lifelong disorder with well-established diagnostic procedures and etiology, from other syndromes with hypersomnolence of unknown causes. Klein-Levin Syndrome, a periodic hypersomnia associated with cognitive and behavioral abnormalities, is also considered a separate entity with separate therapeutic protocols. Non hypocretin-related hypersomnia syndromes are diagnoses of exclusion. These diagnoses are only made after eliminating sleep deprivation, sleep apnea, disturbed nocturnal sleep, and psychiatric comorbidities as the primary cause of daytime sleepiness. The treatment of narcolepsy/hypocretin deficiency is well-codified, and involves pharmacotherapies using sodium oxybate, stimulants, and/or antidepressants, plus behavioral modifications. These therapies are almost always needed, and the risk-to-benefit ratio is clear, notably in children. Detailed knowledge of the pharmacological profile of each compound is needed to optimize use. Treatment for other syndromes with hypersomnolence is more challenging and less codified. Preferably, therapy should be conservative (such as modafinil, atomoxetine, behavioral modifications), but it may have to be more aggressive (high-dose stimulants, sodium oxybate, etc.) on a case-by-case, empirical trial basis. As cause and evolution are unknown in these conditions, it is important to challenge diagnosis and therapy over time, keeping in mind the possibility of tolerance and the development of stimulant addiction. Kleine-Levin Syndrome is usually best left untreated, although lithium can be considered in severe cases with frequent episodes. Guidelines are provided based on the literature and personal experience of the author.

          Electronic supplementary material

          The online version of this article (doi:10.1007/s13311-012-0150-9) contains supplementary material, which is available to authorized users.

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          Most cited references82

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          Imaging dopamine's role in drug abuse and addiction.

          Dopamine is involved in drug reinforcement but its role in addiction is less clear. Here we describe PET imaging studies that investigate dopamine's involvement in drug abuse in the human brain. In humans the reinforcing effects of drugs are associated with large and fast increases in extracellular dopamine, which mimic those induced by physiological dopamine cell firing but are more intense and protracted. Since dopamine cells fire in response to salient stimuli, supraphysiological activation by drugs is experienced as highly salient (driving attention, arousal, conditioned learning and motivation) and with repeated drug use may raise the thresholds required for dopamine cell activation and signaling. Indeed, imaging studies show that drug abusers have marked decreases in dopamine D2 receptors and in dopamine release. This decrease in dopamine function is associated with reduced regional activity in orbitofrontal cortex (involved in salience attribution; its disruption results in compulsive behaviors), cingulate gyrus (involved in inhibitory control; its disruption results in impulsivity) and dorsolateral prefrontal cortex (involved in executive function; its disruption results in impaired regulation of intentional actions). In parallel, conditioning triggered by drugs leads to enhanced dopamine signaling when exposed to conditioned cues, which then drives the motivation to procure the drug in part by activation of prefrontal and striatal regions. These findings implicate deficits in dopamine activity-inked with prefrontal and striatal deregulation-in the loss of control and compulsive drug intake that results when the addicted person takes the drugs or is exposed to conditioned cues. The decreased dopamine function in addicted individuals also reduces their sensitivity to natural reinforcers. Therapeutic interventions aimed at restoring brain dopaminergic tone and activity of cortical projection regions could improve prefrontal function, enhance inhibitory control and interfere with impulsivity and compulsive drug administration while helping to motivate the addicted person to engage in non-drug related behaviors.
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            Narcolepsy onset is seasonal and increased following the 2009 H1N1 pandemic in China.

            Narcolepsy is caused by the loss of hypocretin/orexin neurons in the hypothalamus, which is likely the result of an autoimmune process. Recently, concern has been raised over reports of narcolepsy in northern Europe following H1N1 vaccination. The study is a retrospective analysis of narcolepsy onset in subjects diagnosed in Beijing, China (1998-2010). Self-reported month and year of onset were collected from 629 patients (86% children). Graphical presentation, autocorrelations, chi-square, and Fourier analysis were used to assess monthly variation in onset. Finally, 182 patients having developed narcolepsy after October 2009 were asked for vaccination history. The occurrence of narcolepsy onset was seasonal, significantly influenced by month and calendar year. Onset was least frequent in November and most frequent in April, with a 6.7-fold increase from trough to peak. Studying year-to-year variation, we found a 3-fold increase in narcolepsy onset following the 2009 H1N1 winter influenza pandemic. The increase is unlikely to be explained by increased vaccination, as only 8 of 142 (5.6%) patients recalled receiving an H1N1 vaccination. Cross-correlation indicated a significant 5- to 7-month delay between the seasonal peak in influenza/cold or H1N1 infections and peak in narcolepsy onset occurrences. In China, narcolepsy onset is highly correlated with seasonal and annual patterns of upper airway infections, including H1N1 influenza. In 2010, the peak seasonal onset of narcolepsy was phase delayed by 6 months relative to winter H1N1 infections, and the correlation was independent of H1N1 vaccination in the majority of the sample. Copyright © 2011 American Neurological Association.
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              Effects of modafinil on dopamine and dopamine transporters in the male human brain: clinical implications.

              Modafinil, a wake-promoting drug used to treat narcolepsy, is increasingly being used as a cognitive enhancer. Although initially launched as distinct from stimulants that increase extracellular dopamine by targeting dopamine transporters, recent preclinical studies suggest otherwise. To measure the acute effects of modafinil at doses used therapeutically (200 mg and 400 mg given orally) on extracellular dopamine and on dopamine transporters in the male human brain. Positron emission tomography with [(11)C]raclopride (D(2)/D(3) radioligand sensitive to changes in endogenous dopamine) and [(11)C]cocaine (dopamine transporter radioligand) was used to measure the effects of modafinil on extracellular dopamine and on dopamine transporters in 10 healthy male participants. The study took place over an 8-month period (2007-2008) at Brookhaven National Laboratory. Primary outcomes were changes in dopamine D(2)/D(3) receptor and dopamine transporter availability (measured by changes in binding potential) after modafinil when compared with after placebo. Modafinil decreased mean (SD) [(11)C]raclopride binding potential in caudate (6.1% [6.5%]; 95% confidence interval [CI], 1.5% to 10.8%; P = .02), putamen (6.7% [4.9%]; 95% CI, 3.2% to 10.3%; P = .002), and nucleus accumbens (19.4% [20%]; 95% CI, 5% to 35%; P = .02), reflecting increases in extracellular dopamine. Modafinil also decreased [(11)C]cocaine binding potential in caudate (53.8% [13.8%]; 95% CI, 43.9% to 63.6%; P < .001), putamen (47.2% [11.4%]; 95% CI, 39.1% to 55.4%; P < .001), and nucleus accumbens (39.3% [10%]; 95% CI, 30% to 49%; P = .001), reflecting occupancy of dopamine transporters. In this pilot study, modafinil blocked dopamine transporters and increased dopamine in the human brain (including the nucleus accumbens). Because drugs that increase dopamine in the nucleus accumbens have the potential for abuse, and considering the increasing use of modafinil, these results highlight the need for heightened awareness for potential abuse of and dependence on modafinil in vulnerable populations.
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                Author and article information

                Contributors
                mignot@stanford.edu
                Journal
                Neurotherapeutics
                Neurotherapeutics
                Neurotherapeutics
                Springer-Verlag (New York )
                1933-7213
                1878-7479
                11 October 2012
                11 October 2012
                October 2012
                : 9
                : 4
                : 739-752
                Affiliations
                Stanford Center for Sleep Sciences and Medicine, Stanford University Medical School, Palo Alto, CA 94304 USA
                Article
                150
                10.1007/s13311-012-0150-9
                3480574
                23065655
                37e1904d-8a69-4c6f-b0c9-981dfc650737
                © The Author(s) 2012
                History
                Categories
                Article
                Custom metadata
                © The American Society for Experimental NeuroTherapeutics, Inc. 2012

                Neurology
                hypocretin,orexin,sodium oxybate,modafinil,narcolepsy,venlafaxine
                Neurology
                hypocretin, orexin, sodium oxybate, modafinil, narcolepsy, venlafaxine

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