Improved vigilance after sodium oxybate treatment in narcolepsy: a comparison between in-field and in-laboratory measurements

Impaired cognition in narcolepsy: clinical and neurobiological perspectives

In addition to well-known symptoms such as sleepiness and cataplexy, many people with narcolepsy have impaired cognition, reporting inattention, poor memory, and other concerns. Unfortunately, research on cognition in narcolepsy has been limited. Strong evidence demonstrates difficulties with sustained attention, but evidence for executive dysfunction and impaired memory is mixed. Animal research provides some insights into how loss of the orexin neurons in narcolepsy type 1 may give rise to impaired cognition via dysfunction of the prefrontal cortex, and cholinergic and monoaminergic systems. This paper reviews some of these clinical and preclinical findings, provides a neurobiological framework to understand these deficits, and highlights some of the many key unanswered questions.

Executive function performance in children and adolescent patients with narcolepsy type 1

OBJECTIVE

The executive function profile in patients with narcolepsy type 1 (NT1) has been mentioned; however, limited research exists on children and adolescent patients with NT1.This study aims to assess executive function in children and adolescent patients with NT1 in China, examine potential influencing factors and evaluate the short-term treatment effect on executive function.

METHODS

53 NT1 patients (36 males, age 12.2 ± 3.4 years) and 37 healthy controls (23 males, age 12.2 ± 2.5 years) underwent self-reported measures assessing subjective sleepiness, depression, anxiety and sleep quality. A comprehensive neuropsychological test was administered to assess executive function domains, including processing speed, inhibitory control, cognitive flexibility and working memory. These assessments were repeated in NT1 patients after three-day regular drug treatment.

RESULTS

NT1 patients exhibited higher levels of excessive daytime sleepiness, depression, anxiety, and poor sleep quality compared to healthy controls. Patients showed impaired processing speed, inhibitory control and cognitive flexibility (p < 0.05), whereas working memory was unaffected (p > 0.05). Regression analysis revealed that parameters from sleep monitoring, such as sleep efficiency and sleep latency, were correlated with executive function performance after controlling for age, gender, and education years. The short-term treatment led to improvements in inhibitory control, cognitive flexibility, and working memory.

CONCLUSION

The findings showed that executive function was impaired among children and adolescent patients with NT1, which was associated with objective sleep parameters. Furthermore, this study emphasizes the necessity of neuropsychological assessments and early interventions among children and adolescent NT1 patients.

Accidental calcium, magnesium, potassium and sodium oxybates (Xywave) overdose: mistiming of a single night's narcolepsy medication leading to respiratory failure requiring mechanical ventilation

While typically thought of as an illicit substance, oxybate salts or gamma-hydroxybutyrate (GHB) has more recently been prescribed to treat narcolepsy by enhancing night-time sleep resulting in decreased daytime drowsiness. This case involves a college-aged female with prescribed GHB for narcolepsy who took her second nightly dose too early. This resulted in mental depression, respiratory failure, intubation and mechanical ventilation. The patient was successfully extubated in the intensive care unit several hours later with no residual morbidity. We were unable to identify any prior reports of mixed-salt oxybate toxicity following mistimed drug administration. This case should serve as a warning to emergency physicians to be on the lookout for GHB as part of the differential diagnosis for patients with narcolepsy presenting with altered mental status. It should also serve as a warning to patients and prescribers that this medication can have outcomes that require immediate medical intervention.

Objective evaluation of excessive daytime sleepiness

Excessive daytime sleepiness (EDS) is multifactorial. It combines, among other things, an excessive propensity to fall asleep ("physiological sleepiness") and a continuous non-imperative sleepiness (or drowsiness/hypo-arousal) leading to difficulties remaining awake and maintaining sustained attention and vigilance over the long term ("manifest sleepiness"). There is no stand-alone biological measure of EDS. EDS measures can either capture the severity of physiological sleepiness, which corresponds to the propensity to fall asleep, or the severity of manifest sleepiness, which corresponds to behavioral consequences of sleepiness and reduced vigilance. Neuropsychological tests (The psychomotor vigilance task (PVT), Oxford Sleep Resistance Test (OSLeR), Sustained Attention to Response Task (SART)) explore manifest sleepiness through several sustained attention tests but the lack of normative values and standardized protocols make the results difficult to interpret and use in clinical practice. Neurophysiological tests explore the two main aspects of EDS, i.e. the propensity to fall asleep (Multiple sleep latency test, MSLT) and the capacity to remain awake (Maintenance of wakefulness test, MWT). The MSLT and the MWT are widely used in clinical practice. The MSLT is recognized as the "gold standard" test for measuring the severity of the propensity to fall asleep and it is a diagnostic criterion for narcolepsy. The MWT measures the ability to stay awake. The MWT is not a diagnostic test as it is recommended only to evaluate the evolution of EDS and efficacy of EDS treatment. Even if some efforts to standardize the protocols for administration of these tests have been ongoing, MSLT and MWT have numerous limitations: age effect, floor or ceiling effects, binding protocol, no normal or cutoff value (or determined in small samples), and no or low test-retest values in some pathologies. Moreover, the recommended electrophysiological set-up and the determination of sleep onset using the 30‑sec epochs scoring rule show some limitations. New, more precise neurophysiological techniques should aim to detect very brief periods of physiological sleepiness and, in the future, the brain local phenomenon of sleepiness likely to underpin drowsiness, which could be called "physiological drowsiness".

Applicability of the Sustained Attention to Response Task (SART) in hypersomnolence: Experience and results from a tertiary referral center

OBJECTIVE/BACKGROUND

Evaluation of hypersomnolence disorders ideally includes an assessment of vigilance using the short Sustained Attention to Response Task (SART). We evaluated whether this task can differentiate between hypersomnolence disorders, whether it correlates with subjective and objective sleepiness, whether it is affected by the time of day, and symptoms of anxiety and depression.

PATIENTS/METHODS

We analyzed diagnostic data of 306 individuals with hypersomnolence complaints diagnosed with narcolepsy type 1 (n=100), narcolepsy type 2 (n=20), idiopathic hypersomnia (n=49), obstructive sleep apnea (n=27) and other causes or without explanatory diagnosis (n=110). We included the Multiple Sleep Latency Test (MSLT), polysomnography, Epworth Sleepiness Scale (ESS), Hospital Anxiety and Depression Scale and SART, which were administered five times during the day (outcomes: reaction time, total, commission and omission errors).

RESULTS

The SART outcomes did not differ between groups when adjusted for relevant covariates. Higher ESS scores were associated with longer reaction times and more commission errors (p<.01). The main outcome, total errors, did not differ between times of the day. Reaction times and omission errors were impacted (p<.05).

CONCLUSIONS

The SART quantifies disturbed vigilance, an important dimension of disorders of hypersomnolence. Results do not suggest that depressive symptoms influence SART outcomes. A practice session is advised. Testing time should be taken into account when interpreting results. We conclude that the SART does not differentiate between central disorders of hypersomnolence. It may be a helpful addition to the standard diagnostic workup and monitoring of these disorders.

The Treatment of Parkinson's Disease with Sodium Oxybate

Sodiun Oxybate (SO) has a number of attributes that may mitigate the metabolic stress on the substantia nigra pars compacta (SNpc) dopaminergic (DA) neurons in Parkinson's disease (PD). These neurons function at the borderline of energy sufficiency. SO is metabolized to succinate and supplies energy to the cell by generating ATP. SO is a GABAB agonist and, as such, also arrests the high energy requiring calcium pace-making activity of these neurons. In addition, blocking calcium entry impedes the synaptic release and subsequent neurotransmission of aggregated synuclein species. As DA neurons degenerate, a homeostatic failure exposes these neurons to glutamate excitotoxicity, which in turn accelerates the damage. SO inhibits the neuronal release of glutamate and blocks its agonistic actions. Most important, SO generates NADPH, the cell's major antioxidant cofactor. Excessive free radical production within DA neurons and even more so within activated microglia are early and key features of the degenerative process that are present long before the onset of motor symptoms. NADPH maintains cell glutathione levels and alleviates oxidative stress and its toxic consequences. SO, a histone deacetylase inhibitor also suppresses the expression of microglial NADPH oxidase, the major source of free radicals in Parkinson brain. The acute clinical use of SO at night has been shown to reduce daytime sleepiness and fatigue in patients with PD. With long-term use, its capacity to supply energy to DA neurons, impede synuclein transmission, block excitotoxicity and maintain an anti-oxidative redox environment throughout the night may delay the onset of PD and slow its progress.

Sleep-Related Drug Therapy in Special Conditions: Children

Pharmacologic treatment of the most common pediatric sleep disorders lacks evidence, and alternative methods, which have been proved to alleviate the symptoms, are preferred in most cases. The implementation of specific guidelines is of great importance because sleep disorders in children are not rare and they can negatively affect children's development and their cognitive and social skills. This article summarizes the current therapeutic management of sleep disorders in children, bearing in mind the absence of evidence-based guidelines on this topic.

Usefulness of the maintenance of wakefulness test in central disorders of hypersomnolence: a scoping review

Study Objectives

To review the Maintenance of Wakefulness Test (MWT) as assessment of daytime sleepiness in the evaluation of treatment effects and driving fitness in central disorders of hypersomnolence (CDH).

Methods

We performed a scoping review of studies using the MWT in patients with CDH (i.e. narcolepsy types 1 and 2, and idiopathic hypersomnia). N = 20 articles were included, comprising 683 patients and 129 controls. MWT effect sizes were compared to the Clinical Global Impression (GCI) scale and the Epworth Sleepiness Scale (ESS). MWT sleep latency was correlated to objective driving performances. The role of motivation was evaluated by comparing MWTs of treatment studies (low motivation) to driving fitness studies (high motivation to stay awake). Healthy controls were compared to norm values.

Results

MWT and CGI were both impacted by the same treatment; however, the MWT has higher effect sizes and was more sensitive to measure these effects. The MWT correlated fairly to moderately (ρ = −0.26 to −0.56; p ≤ .05) to objective driving performance. Motivation played a major role on MWT sleep latencies (d = 0.76 to 1.43; p ≤ .001). Current norm values may not be valid, as sleep latency may be impacted by age.

Conclusions

The MWTs applicability to measure treatment effects in CDH was confirmed, but age-adjusted norm values are needed. For a more complete evaluation of EDS it should be combined with subjective measures. Its reliability for driving fitness evaluation is insufficient, and motivation plays a major role. To predict or monitor driving performance in CDH, valid and easy methods should be developed.

The Psychomotor Vigilance Test as a measure of alertness and sleep inertia in people with central disorders of hypersomnolence

STUDY OBJECTIVES

The central disorders of hypersomnolence (CDH) manifest with daytime sleepiness, often accompanied by cognitive symptoms. Objective tests characterizing cognitive dysfunction may have diagnostic utility. Further, because some people with CDH report worsening cognition upon awakening, cognitive testing before and after napping may provide additional diagnostic information.

METHODS

Patients with CDH with idiopathic hypersomnia (n = 76), narcolepsy type 1 (n = 19), narcolepsy type 2 (n = 22), and self-reported excessive daytime sleepiness not meeting current diagnostic criteria (n = 76) and nonsleepy controls (n = 33) underwent testing with the Psychomotor Vigilance Test (PVT), a 10-minute reaction-time test. A subset of participants underwent repeat testing during a Multiple Sleep Latency Test, before and immediately after naps 2 and 4.

RESULTS

Most PVT metrics were significantly better in controls than in patients with CDH. Minimal group differences in PVT performance were observed by CDH diagnosis. PVT performance was weakly correlated to Epworth Sleepiness Scale and Multiple Sleep Latency Test mean sleep latency in the CDH group. Before and after naps, PVT metrics were minimally different for controls, while PVT performance generally worsened following naps in the CDH group, with significant worsening compared with controls for nap 2 mean, median, lapses, and fastest 10% of responses and nap 4 lapses and slowest 10% of responses. Change in performance did not differ based on CDH diagnostic group for any metric on either nap.

CONCLUSIONS

The PVT, at baseline and following a short nap, may provide adjunctive diagnostic utility in separating individuals with CDH from controls.

CITATION

Trotti LM, Saini P, Bremer E, et al. The Psychomotor Vigilance Test as a measure of alertness and sleep inertia in people with central disorders of hypersomnolence. J Clin Sleep Med. 2022;18(5):1395-1403.

Toxicological Characterization of GHB as a Performance-Enhancing Drug

Performance-enhancing drugs (PEDs) are represented by several compounds used to ameliorate the image, the appearance, or an athletic or non-athletic performance. Gamma-hydroxybutyrate (GHB) is an endogenous molecule first used as anesthetic and then marketed as a nutritional supplement with a wide diffusion in the bodybuilding community. The aim of the present work is to provide a toxicological characterization of the use of GHB as a PED, including the scientific basis for its use, the patterns of use/abuse, and the health risks arising from its consumption in this peculiar recreative setting. A literature search was performed on multiple databases including experimental studies on humans and animals as well as epidemiological reports and forensic case reports/series. Experimental studies demonstrated that the use of GHB as a PED is motivated by the release of growth hormone and the induction of sleep. However, the panel of desired performance-related effects was much wider in real cases and epidemiological studies. Even though the use of GHB among bodybuilders has decreased, its use to enhance some kind of performance, particularly sexual ones or social-communicative ones, as well as means to increase mood and perceived energy, is still common.

Treatment of central disorders of hypersomnolence: an American Academy of Sleep Medicine systematic review, meta-analysis, and GRADE assessment

INTRODUCTION

This systematic review provides supporting evidence for the accompanying clinical practice guideline on the treatment of central disorders of hypersomnolence in adults and children. The review focuses on prescription medications with U.S. Food & Drug Administration approval and nonpharmacologic interventions studied for the treatment of symptoms caused by central disorders of hypersomnolence.

METHODS

The American Academy of Sleep Medicine commissioned a task force of experts in sleep medicine to perform a systematic review. Randomized controlled trials and observational studies addressing pharmacological and nonpharmacological interventions for central disorders of hypersomnolence were identified. Statistical analyses were performed to determine the clinical significance of all outcomes. Finally, the Grading of Recommendations Assessment, Development and Evaluation (GRADE) process was used to assess the evidence for the purpose of making specific treatment recommendations.

RESULTS

The literature search identified 678 studies; 144 met the inclusion criteria and 108 provided data suitable for statistical analyses. Evidence for the following interventions is presented: armodafinil, clarithromycin, clomipramine, dextroamphetamine, flumazenil, intravenous immune globulin (IVIG), light therapy, lithium, l-carnitine, liraglutide, methylphenidate, methylprednisolone, modafinil, naps, pitolisant, selegiline, sodium oxybate, solriamfetol, and triazolam. The task force provided a detailed summary of the evidence along with the quality of evidence, the balance of benefits and harms, patient values and preferences, and resource use considerations.

CITATION

Maski K, Trotti LM, Kotagal S, et al. Treatment of central disorders of hypersomnolence: an American Academy of Sleep Medicine systematic review, meta-analysis, and GRADE assessment. J Clin Sleep Med. 2021;17(9):1895-1945.

Cognitive dysfunction in central disorders of hypersomnolence: A systematic review

Central disorders of hypersomnolence (CDH) are characterized by excessive daytime sleepiness not related to comorbid sleep or medical disturbances. We systematically examined scientific literature on cognitive functions in patients suffering from CDH. Forty-eight studies proved eligible and were analyzed separately for Narcolepsy Type 1 (NT1), Narcolepsy Type 2 (NT2), Idiopathic hypersomnia (IH) and Kleine-Levin syndrome (KLS). Results were grouped into the cognitive domains of attention, memory, executive functions and higher order cognition. Consistent attention impairments emerged in NT1, NT2 and IH patients, with NT1 patients showing the most compromised profile. Memory functions are largely unimpaired in CDH patients except for KLS patients who display memory deficit. Executive functions and higher-order cognition have been assessed in NT1 while they received little-to-no attention in the other CDH. NT1 patients display high performance in executive functions but exhibit a complex pattern of impairment in higher-order cognition, showing poor decision-making and impaired emotional processing. Moreover, NT1 patients show increased creative abilities. Assessing and monitoring cognitive impairments experienced by CDH patients will allow the design of personalized interventions, parallel to pharmacological treatment, aimed at improving daytime functioning and quality of life of these patients.

Sleep, Narcolepsy, and Sodium Oxybate

Sodium oxybate (SO) has been in use for many decades to treat narcolepsy with cataplexy. It functions as a weak GABAB agonist but also as an energy source for the brain as a result of its metabolism to succinate and as a powerful antioxidant because of its capacity to induce the formation of NADPH. Its actions at thalamic GABAB receptors can induce slow-wave activity, while its actions at GABAB receptors on monoaminergic neurons can induce or delay REM sleep. By altering the balance between monoaminergic and cholinergic neuronal activity, SO uniquely can induce and prevent cataplexy. The formation of NADPH may enhance sleep’s restorative process by accelerating the removal of the reactive oxygen species (ROS), which accumulate during wakefulness. SO improves alertness in normal subjects and in patients with narcolepsy. SO may allay severe psychological stress - an inflammatory state triggered by increased levels of ROS and characterized by cholinergic supersensitivity and monoaminergic deficiency. SO may be able to eliminate the inflammatory state and correct the cholinergic/ monoaminergic imbalance.

On-the-road driving performance of patients with central disorders of hypersomnolence

INTRODUCTION

Excessive Daytime Sleepiness is a core symptom of narcolepsy and idiopathic hypersomnia, which impairs driving performance. Adequate treatment improves daytime alertness, but it is unclear whether driving performance completely normalizes. This study compares driving performance of patients with narcolepsy and idiopathic hypersomnia receiving treatment to that of healthy controls.

METHODS

Patients diagnosed with narcolepsy type 1 (NT1, n = 33), narcolepsy type 2 (NT2, n = 7), or idiopathic hypersomnia (IH, n = 6) performed a standardized one-hour on-the-road driving test, measuring standard deviation of lateral position (SDLP).

RESULTS

Results showed that mean SDLP in patients did not differ significantly from controls, but the 95%CI of the mean difference (+1.02 cm) was wide (-0.72 to +2.76 cm). Analysis of subgroups, however, showed that mean SDLP in NT1 patients was significantly increased by 1.90 cm as compared to controls, indicating impairment. Moreover, four NT1 patients requested to stop the test prematurely due to self-reported somnolence, and two NT1 patients were stopped by the driving instructor for similar complaints.

CONCLUSION

Driving performance of NT1 patients may still be impaired, despite receiving treatment. No conclusions can be drawn for NT2 and IH patients due to the low sample sizes of these subgroups. In clinical practice, determination of fitness to drive for these patients should be based on an individual assessment in which also coping strategies are taken into account.

Neuropsychological Alterations in Narcolepsy with Cataplexy and the Expression of Cognitive Deficits

OBJECTIVES

The objective of our study was to assess attention processes and executive function in patients with narcolepsy with cataplexy (NT1). To do so, we compared the results with those of a control group from the general population using an extensive neuropsychological test battery.

METHODS

We studied 28 patients with NT1 and 28 healthy control participants matched for age, gender, and educational level. They all completed questionnaires on sleepiness, anxiety, and depression symptoms. In addition, they underwent neuropsychological tests. The ability to maintain attention was assessed using three computer tasks with different levels of complexity.

RESULTS

Patients had significantly more daytime sleepiness than controls. A significant negative correlation between depression and disease duration was found in NT1 patients. The results of the anxiety questionnaire correlated with the presence of sleep paralysis. There were significant differences in information processing speed subtasks. Patients made significantly more omissions and generally reacted slower and more variably than controls in computerized tasks. As for executive function, patients performed worse in phonologic fluency tasks than controls. However, when the influence of processing speed on fluency tasks was statistically controlled, part of this significant difference disappeared.

CONCLUSIONS

Our results indicate that the negative correlation between depression and disease duration probably reflects progressive adaptation to the functional burden of the disease. Information processing speed plays a fundamental role in the expression of cognitive deficits. We emphasized the need to control the influence of processing speed and sustained attention in the neuropsychological assessment of NT1 patients.

Sleep-Related Drug Therapy in Special Conditions: Children

Sleep disorders in children may lead to neurodevelopmental and neurocognitive deficits; it is important to diagnose and treat them properly. Apart from the existing challenges in diagnosis, another drawback is that few therapies are currently approved. In this article, a comprehensive summary of the most common pediatric sleep disorders, along with the various pharmacologic and nonpharmacologic approaches for their management, is presented. Special attention has been paid to the currently available treatment options for pediatric insomnia, obstructive sleep apnea, parasomnias, narcolepsy, and restless legs syndrome, and comparisons are made with the corresponding treatment options for sleep disorders in adults.

Treatment of narcolepsy and other organic hypersomnias in children

The comprehensive management of chronic disorders such as hypersomnias of childhood requires combining life-style changes with rational pharmacotherapy that is based on treating the symptoms that are most bothersome, the age, comorbidities, and metabolic and endocrine status of the patient. The excessive sleepiness of narcolepsy and idiopathic hypersomnia is best treated with dextroamphetamine or methylphenidate preparations or modafinil/armodafinil. Cataplexy treatment requires sodium oxybate, tricyclic agents, selective norepinephrine reuptake inhibitors or selective serotonin reuptake inhibitors. Sodium oxybate is approved only for adults, thus its use in children is only on an off-label basis. Dual therapy, with both anti-cataplectic and stimulant medications may be required, as is close monitoring for treatment-emergent side effects.

The cost-utility of sodium oxybate as narcolepsy treatment

AIMS AND OBJECTIVES

Based on class-I studies, sodium oxybate is regarded as a first-line treatment for both EDS and cataplexy. The cost-effectiveness of sodium oxybate is largely unknown, though. In this study, we estimate the cost-effectiveness of sodium oxybate as treatment for patients with narcolepsy as compared to standard treatment, by calculating incremental cost-effectiveness ratios (cost per quality-adjusted life year, QALY) for patients in a Swedish setting.

MATERIALS AND METHODS

Calculations were performed using a Markov model with a 10-year time horizon. The study population consisted of adult patients treated for narcolepsy with cataplexy. Healthcare utilization and quality-adjusted life years (QALYs) for each treatment alternative were calculated assuming no treatment effect on survival. Sensitivity analyses were performed for treatment effectiveness and healthcare cost parameters.

RESULTS

The cost per additional quality-adjusted life year was estimated at SEK 563,481. The cost-effectiveness measure was demonstrated to be particularly sensitive to the duration of the relative quality-of-life improvements accruing to patients treated with sodium oxybate.

CONCLUSIONS

The estimated cost per additional QALY for the sodium oxybate treatment alternative compared with standard treatment was estimated above the informal Swedish willingness-to-pay threshold (SEK 500,000). The estimated cost per additional QALY obtained here is likely to overestimate the true cost-effectiveness ratio as potentially beneficial effects on productivity of treatment with sodium oxybate were not included (due to lack of data).

Narcolepsy

Narcolepsy is a chronic sleep disorder that has a typical onset in adolescence and is characterized by excessive daytime sleepiness, which can have severe consequences for the patient. Problems faced by patients with narcolepsy include social stigma associated with this disease, difficulties in obtaining an education and keeping a job, a reduced quality of life and socioeconomic consequences. Two subtypes of narcolepsy have been described (narcolepsy type 1 and narcolepsy type 2), both of which have similar clinical profiles, except for the presence of cataplexy, which occurs only in patients with narcolepsy type 1. The pathogenesis of narcolepsy type 1 is hypothesized to be the autoimmune destruction of the hypocretin-producing neurons in the hypothalamus; this hypothesis is supported by immune-related genetic and environmental factors associated with the disease. However, direct evidence in support of the autoimmune hypothesis is currently unavailable. Diagnosis of narcolepsy encompasses clinical, electrophysiological and biological evaluations, but simpler and faster procedures are needed. Several medications are available for the symptomatic treatment of narcolepsy, all of which have quite good efficacy and safety profiles. However, to date, no treatment hinders or slows disease development. Improved diagnostic tools and increased understanding of the pathogenesis of narcolepsy type 1 are needed and might lead to therapeutic or even preventative interventions.