Recent Advances in the Treatment of Narcolepsy

Narcolepsy Beyond Medication: A Scoping Review of Psychological and Behavioral Interventions for Patients with Narcolepsy

Objectives: The present scoping review aims to map the existing evidence on psychological and behavioral interventions targeting patients with narcolepsy type 1 and type 2. Methods: A literature search was performed using the databases Scopus, PubMed, and PsycINFO. Studies were included if they (1) employed randomized controlled trials, non-randomized trials, or quasi-experimental studies; (2) were published in English; (3) were published in peer-reviewed journals; (4) examined the impact of psychological interventions on psychopathological (primary outcomes) and narcolepsy-related symptoms (secondary outcomes); and (5) involved patients with a diagnosis of narcolepsy using recognized diagnostic criteria regardless of whether they were receiving pharmacological treatment or were untreated. No restrictions were imposed on the publication date to comprehensively map the available evidence. Data were extracted to address the review aims and presented as a narrative synthesis. Results: The database search yielded six studies. Treatment options for individuals with narcolepsy encompass psychological and behavioral interventions, such as telehealth interventions, meditation/relaxation therapy, and scheduled napping. The primary outcomes were daytime sleepiness, wakefulness maintenance, sleep attacks, the severity of symptoms of narcolepsy, sleep paralysis episodes, depression, and psychological functioning. The secondary outcomes were sleep-problem-related quality of life, sleep inertia, and sleep quality. The psychological and behavioral interventions exhibited variability in terms of the intervention type, personnel involved, number of sessions, and duration. Most of the contributions also lack details regarding the training of professionals and the specifics of the interventions. Additionally, the evidence quality was deemed low based on the Crowe Critical Appraisal Tool. Conclusions: Although the importance of nonpharmacological approaches is well recognized, there is limited evidence to support the efficacy of psychological and behavioral interventions in narcolepsy. This is further complicated by the wide range of psychological and behavioral interventions available.

Pharmacologic Management of Excessive Daytime Sleepiness

Excessive daytime sleepiness (EDS) is defined as "irresistible sleepiness in a situation when an individual would be expected to be awake, and alert." EDS has been a big concern not only from a medical but also from a public health point of view. Patients with EDS have the possibility of falling asleep even when they should wake up and concentrate, for example, when they drive, play sports, or walk outside. In this article, clinical characteristics of common hypersomnia and pharmacologic treatments of each hypersomnia are described.

Pharmacologic Management of Excessive Daytime Sleepiness

Excessive daytime sleepiness (EDS) is related to medical and social problems, including mental disorders, physical diseases, poor quality of life, and so forth. According to the International Classification of Sleep Disorders, Third Edition, diseases that result from EDS are narcolepsy type 1, narcolepsy type 2, idiopathic hypersomnia, hypersomnia due to a medical disorder, and others. EDS is usually treated using amphetamine-like central nervous system stimulants or modafinil and its R-enantiomer, armodafinil, wake-promoting compounds unrelated to amphetamines; a variety of new drugs are under development. The side effects of some stimulants are potent and careful selection and management are required.

Pharmacologic Management of Excessive Daytime Sleepiness

Excessive daytime sleepiness (EDS) is related to medical and social problems, including mental disorders, physical diseases, poor quality of life, and so forth. According to the International Classification of Sleep Disorders, Third Edition, diseases that result from EDS are narcolepsy type 1, narcolepsy type 2, idiopathic hypersomnia, hypersomnia due to a medical disorder, and others. EDS is usually treated using amphetamine-like central nervous system stimulants or modafinil and its R-enantiomer, armodafinil, wake-promoting compounds unrelated to amphetamines; a variety of new drugs are under development. The side effects of some stimulants are potent and careful selection and management are required.

Evaluation of CNS involvement in myotonic dystrophy type 1 and type 2 by transcranial sonography

Myotonic dystrophies (DMs) are clinically similar but distinct multisystemic diseases related to different repeat expansion mutations. CNS involvement is one important aspect of both, myotonic dystrophy type 1 and type 2 (DM1, DM2). Transcran ial sonography (TCS) has become a reliable diagnostic tool in the evaluation of several CNS disorders. The aim of this study was to evaluate TCS-findings in DM-patients in correlation with their clinical status. Thirty-one DM-patients (DM1 = 17; DM2 = 14) were examined clinically and sonographically by independent physicians. Echogenicities of basal ganglia and mesencephalic regions were assessed according to the examination protocol for extrapyramidal disorders using a Toshiba Aplio(®) XG ultrasound system. TCS abnormalities were correlated to clinical findings and secondly compared to 31 controls. Ventricle diameters were additionally compared to 3T-MRI volumetry. Nine patients (29 %) showed hyperechogenicity of substantia nigra. Mesencephalic raphe was hypoechogenic in nine (29 %) DM-patients and was more frequently in DM1 patients (p = 0.021). Width of third ventricle was significantly larger in the patient group (p = 0.021) and correlated with MRI-based volumetry (R (2) = 0.756). Pathological raphe signal was observed mainly in patients suffering from daytime sleepiness (sensitivity = 42.1 %, specificity = 88.9 %, p = 0,044), while alterations did not correlate with symptoms of depression. As a novel finding, a relation between mesencephalic raphe echogenicity and excessive daytime sleepiness could be identified in our DM-patients. An alteration of serotonergic raphe structures might be involved in the pathogenesis of hypersomnia in DM. TCS allows for measurement of third ventricle enlargement as a feasible bedside test.

Conditional ablation of orexin/hypocretin neurons: a new mouse model for the study of narcolepsy and orexin system function

The sleep disorder narcolepsy results from loss of hypothalamic orexin/hypocretin neurons. Although narcolepsy onset is usually postpubertal, current mouse models involve loss of either orexin peptides or orexin neurons from birth. To create a model of orexin/hypocretin deficiency with closer fidelity to human narcolepsy, diphtheria toxin A (DTA) was expressed in orexin neurons under control of the Tet-off system. Upon doxycycline removal from the diet of postpubertal orexin-tTA;TetO DTA mice, orexin neurodegeneration was rapid, with 80% cell loss within 7 d, and resulted in disrupted sleep architecture. Cataplexy, the pathognomic symptom of narcolepsy, occurred by 14 d when ∼5% of the orexin neurons remained. Cataplexy frequency increased for at least 11 weeks after doxycycline. Temporary doxycycline removal followed by reintroduction after several days enabled partial lesion of orexin neurons. DTA-induced orexin neurodegeneration caused a body weight increase without a change in food consumption, mimicking metabolic aspects of human narcolepsy. Because the orexin/hypocretin system has been implicated in the control of metabolism and addiction as well as sleep/wake regulation, orexin-tTA; TetO DTA mice are a novel model in which to study these functions, for pharmacological studies of cataplexy, and to study network reorganization as orexin input is lost.

Orexin neurons suppress narcolepsy via 2 distinct efferent pathways

The loss of orexin neurons in humans is associated with the sleep disorder narcolepsy, which is characterized by excessive daytime sleepiness and cataplexy. Mice lacking orexin peptides, orexin neurons, or orexin receptors recapitulate human narcolepsy phenotypes, further highlighting a critical role for orexin signaling in the maintenance of wakefulness. Despite the known role of orexin neurons in narcolepsy, the precise neural mechanisms downstream of these neurons remain unknown. We found that targeted restoration of orexin receptor expression in the dorsal raphe (DR) and in the locus coeruleus (LC) of mice lacking orexin receptors inhibited cataplexy-like episodes and pathological fragmentation of wakefulness (i.e., sleepiness), respectively. The suppression of cataplexy-like episodes correlated with the number of serotonergic neurons restored with orexin receptor expression in the DR, while the consolidation of fragmented wakefulness correlated with the number of noradrenergic neurons restored in the LC. Furthermore, pharmacogenetic activation of these neurons using designer receptor exclusively activated by designer drug (DREADD) technology ameliorated narcolepsy in mice lacking orexin neurons. These results suggest that DR serotonergic and LC noradrenergic neurons play differential roles in orexin neuron-dependent regulation of sleep/wakefulness and highlight a pharmacogenetic approach for the amelioration of narcolepsy.

Sleep medicine pharmacotherapeutics overview: today, tomorrow, and the future (part 2: hypersomnia, parasomnia, and movement disorders)

Over the past 10 years, significant strides have been made in therapeutics for sleep disorders. In this second installment of a two-part review series, we discuss the current evidence surrounding the mechanisms of actions, indications, efficacy, and adverse side effects associated with the current over-the-counter and pharmacotherapeutics for hypersomnia, parasomnias, and movement disorders of sleep.

Methylphenidate-mediated reduction in prefrontal hemodynamic responses to working memory task: a functional near-infrared spectroscopy study

OBJECTIVE

Functional near-infrared spectroscopy (fNIRS) is a non-invasive optical technique for bedside evaluation of cerebral metabolism that has clinical potential for monitoring the efficacy of pharmacological treatment. In this pilot study, we investigated the cognitive effects of methylphenidate (MP) on prefrontal function using fNIRS in healthy subjects.

METHODS

Thirteen right-handed healthy subjects underwent working memory tasks (0-back and 2-back) after a single oral dose of MP (20 mg) or placebo administered in a double-blind crossover design on two different days separated by 1-3 days. We measured changes in oxyhemoglobin (oxy-Hb) and deoxyhemoglobin (deoxy-Hb) concentrations during the tasks in bilateral prefrontal regions after MP or placebo administration using two-channel fNIRS.

RESULTS

There were significantly more correct responses and fewer missed responses during the 2-back task performance after MP treatment as compared with placebo. Baseline-corrected oxy-Hb was significantly decreased after MP treatment compared with the placebo in the 2-back task in the right frontal region but was not different in the 0-back task. Baseline-corrected deoxy-Hb and total-Hb concentrations were not significant between MP and placebo conditions in either of the cognitive tasks.

CONCLUSIONS

These data are consistent with previous positron emission tomography findings of MP-mediated reduction in lateral prefrontal activity accompanied by improved cognitive performance.

Cognitive-enhancing substance use at German universities: frequency, reasons and gender differences

BACKGROUND

The purpose of this study was to give an overview whether German students regularly use stimulants for enhancing their academic performance. Reasons associated with the use of these substances were explored. Moreover, gender differences were analyzed.

METHODS

A cross-sectional survey study was performed analyzing a random sample of 1,053 students of different fields of study in Germany. Students were asked to complete an anonymous self-administered web-based survey containing questions on cognitive performance-enhancing substance use. We used statistical analyses, e.g. non-parametric tests to evaluate the data of our questionnaire.

RESULTS

Among 1,053 students, 61 % responded to our questionnaire. The average age was M = 24.58; 635 participants were female and 418 were male students. Total 1-13 % of the participating students have taken prescription stimulants (e.g. modafinil) or illicit drugs (e.g. cannabis) at least once in their lifetime. The most common reasons for taking stimulants were to support concentration, to relax and to increase alertness. We found significant gender differences with regard to frequency and reason for using performance-enhancing substances.

CONCLUSIONS

Our study results give an overview about the actual situation on frequency and reasons for taking performance-enhancing substances. Departments of Public Health should address this issue in national health debates and discussions. Based on our study findings health education programmes should be developed.

Methylphenidate exposure induces dopamine neuron loss and activation of microglia in the basal ganglia of mice

Background

Methylphenidate (MPH) is a psychostimulant that exerts its pharmacological effects via preferential blockade of the dopamine transporter (DAT) and the norepinephrine transporter (NET), resulting in increased monoamine levels in the synapse. Clinically, methylphenidate is prescribed for the symptomatic treatment of ADHD and narcolepsy; although lately, there has been an increased incidence of its use in individuals not meeting the criteria for these disorders. MPH has also been misused as a “cognitive enhancer” and as an alternative to other psychostimulants. Here, we investigate whether chronic or acute administration of MPH in mice at either 1 mg/kg or 10 mg/kg, affects cell number and gene expression in the basal ganglia.

Methodology/Principal Findings

Through the use of stereological counting methods, we observed a significant reduction (∼20%) in dopamine neuron numbers in the substantia nigra pars compacta (SNpc) following chronic administration of 10 mg/kg MPH. This dosage of MPH also induced a significant increase in the number of activated microglia in the SNpc. Additionally, exposure to either 1 mg/kg or 10 mg/kg MPH increased the sensitivity of SNpc dopaminergic neurons to the parkinsonian agent 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Unbiased gene screening employing Affymetrix GeneChip® HT MG-430 PM revealed changes in 115 and 54 genes in the substantia nigra (SN) of mice exposed to 1 mg/kg and 10 mg/kg MPH doses, respectively. Decreases in the mRNA levels of gdnf, dat1, vmat2, and th in the substantia nigra (SN) were observed with both acute and chronic dosing of 10 mg/kg MPH. We also found an increase in mRNA levels of the pro-inflammatory genes il-6 and tnf-α in the striatum, although these were seen only at an acute dose of 10 mg/kg and not following chronic dosing.

Conclusion

Collectively, our results suggest that chronic MPH usage in mice at doses spanning the therapeutic range in humans, especially at prolonged higher doses, has long-term neurodegenerative consequences.