Cataplexy associated with narcolepsy: epidemiology, pathophysiology and management

Symptom measures in pediatric narcolepsy patients: a review

Purpose

This study aimed to provide a summary of the measures to assess narcoleptic symptoms or complications in pediatric narcolepsy patients.

Methods

We searched in the National Center for Biotechnology Information (NCBI) for measures of narcoleptic symptoms for pediatric patients. Further review was conducted if relevant questionnaires or information were mentioned.

Results

There were only two narcolepsy-specific questionnaires, the narcolepsy severity scale and Ullanlinna Narcolepsy Scale, neither of them was developed or validated in the pediatric population. For cataplexy, all the measures were study-specific diaries and were not validated questionnaires. For excessive daytime sleepiness, the Epworth Sleepiness Scale was most frequently used to measure excessive daytime sleepiness in children. For nighttime sleep, the Children’s Sleep Habits Questionnaire was most frequently used. For depression, the Children Depression Inventory was the most frequently used. For attention-deficit/hyperactivity disorder, the Child Behavior Checklist was the most frequently used. For quality of life, KIDSCREEN was most frequently used.

Conclusions

At present, there is a lack of disease-specific and validated questionnaires for pediatric narcoleptic patients. This need can be met by modifying and adjusting the existing adult questionnaires and developing new questionnaires for pediatric narcoleptic patients.

Narcolepsy and emotional experience: a review of the literature

Narcolepsy is a chronic sleep disorder characterized by excessive daytime sleepiness, cataplexy, hypnagogic hallucinations, and sleep paralysis. This disease affects significantly the overall patient functioning, interfering with social, work, and affective life. Some symptoms of narcolepsy depend on emotional stimuli; for instance, cataplectic attacks can be triggered by emotional inputs such as laughing, joking, a pleasant surprise, and also anger. Neurophysiological and neurochemical findings suggest the involvement of emotional brain circuits in the physiopathology of cataplexy, which seems to depending on the dysfunctional interplay between the hypothalamus and the amygdala associated with an alteration of hypocretin levels. Furthermore, behavioral studies suggest an impairment of emotions processing in narcolepsy-cataplexy (NC), like a probable coping strategy to avoid or reduce the frequency of cataplexy attacks. Consistently, NC patients seem to use coping strategies even during their sleep, avoiding unpleasant mental sleep activity through lucid dreaming. Interestingly, NC patients, even during sleep, have a different emotional experience than healthy subjects, with more vivid, bizarre, and frightening dreams. Notwithstanding this evidence, the relationship between emotion and narcolepsy is poorly investigated. This review aims to provide a synthesis of behavioral, neurophysiological, and neurochemical evidence to discuss the complex relationship between NC and emotional experience and to direct future research.

Patient-Reported Measures of Narcolepsy: The Need for Better Assessment

STUDY OBJECTIVES

Narcolepsy, a chronic disorder of the central nervous system, is clinically characterized by a symptom pentad that includes excessive daytime sleepiness, cataplexy, sleep paralysis, hypnopompic/hypnagogic hallucinations, and disrupted nighttime sleep. Ideally, screening and diagnosis instruments that assist physicians in evaluating a patient for type 1 or type 2 narcolepsy would be brief, easy for patients to understand and physicians to score, and would identify or rule out the need for electrophysiological testing.

METHODS

A search of the literature was conducted to review patient-reported measures used for the assessment of narcolepsy, mainly in clinical trials, with the goal of summarizing existing scales and identifying areas that may require additional screening questions and clinical practice scales.

RESULTS

Of the seven scales reviewed, the Epworth Sleepiness Scale continues to be an important outcome measure to screen adults for excessive daytime sleepiness, which may be associated with narcolepsy. Several narcolepsy-specific scales have demonstrated utility, such as the Ullanlinna Narcolepsy Scale, Swiss Narcolepsy Scale, and Narcolepsy Symptom Assessment Questionnaire, but further validation is required.

CONCLUSIONS

Although the narcolepsy-specific scales currently in use may identify type 1 narcolepsy, there are no validated questionnaires to identify type 2 narcolepsy. Thus, there remains a need for short, easily understood, and well-validated instruments that can be readily used in clinical practice to distinguish narcolepsy subtypes, as well as other hypersomnias, and for assessing symptoms of these conditions during treatment.

Current and future therapeutic approaches in narcolepsy

Narcolepsy with cataplexy (NC) is a disabling orphan sleep disorder characterized by excessive daytime sleepiness, cataplexy and other dissociated manifestations of rapid eye movement sleep (hypnagogic hallucinations and sleep paralysis), as well as frequent movement and awakening during night-time sleep. In this article, we will describe the main symptoms and the current and future treatments of NC. Pathophysiological studies have shown that NC is caused by the early loss of neurons in the hypothalamus that produce hypocretin/orexin, a wakefulness-associated neurotransmitter present in cerebrospinal fluid. The cause of neural loss could be autoimmune since most patients have the human leukocyte antigen DQB1*0602 allele that predisposes individuals to NC. The treatment of narcolepsy has evolved over the past few years with the widespread use of modafinil for daytime sleepiness, antidepressants for cataplexy and γ-hydroxybutyrate (sodium oxybate) for both symptoms. Potential development of new wake-promoting drugs, anticataplectic medications, slow-wave sleep-enhancing treatments, hypocretin-replacement therapy and immunotherapy at early stages of the disease needs to be evaluated in the near future.

Treatment of cataplexy in Niemann-Pick disease type C with the use of miglustat

Cataplexy is the sudden muscle weakness brought on by strong emotions, particularly joking, laughter, or anger. Cataplexy may involve only certain group of muscles or the entire voluntary musculature. In rare cases, symptoms of cataplexy can be seen during the course of some inherited diseases (Niemann-Pick type C (NPC), Prader-Willi syndrome, myotonic dystrophy, Norrie disease). We report the successful use of miglustat, a reversible inhibitor of the enzyme glucosylceramide synthase, approved for use in Gaucher's disease, and which catalyses the first step in the biosynthesis of most glycosphingolipid, in a boy with NPC with cataplexy. A 9-year-old boy was admitted for assessments of frequent "drop attacks" while laughing. The filipin fluorescence tests of cultured skin fibroblasts revealed massive accumulation of unesterified cholesterol, confirming the diagnosis of NPC disease. Molecular studies confirmed the diagnosis of NPC too. After approval from the bioethics committee, miglustat was initiated on the child at 100mg three times a day. Cataplectic attacks disappeared completely after 6 months on treatment, and patient continues to be in remission from the cataplectic attacks at 16 months follow-up. There was no further progression of neurological signs or symptoms or splenomegaly, with some improvement in cognitive function as well as social, affective and attention problems, up-gaze, and gait. Miglustat was well tolerated with no side effects observed. In summary, this is the first report of miglustat treatment of cataplexy in NPC. Long-term follow-up for continuing efficacy and tolerability in a larger cohort with NPC is needed to substantiate our observation.

Treatment of narcolepsy

Narcolepsy is a neurological disorder characterized, in its classical form, by excessive daytime sleepiness (EDS) with irresistible episodes of sleep, cataplexy, disrupted nocturnal sleep, hypnagogic/hypnopompic hallucinations and sleep paralysis. It is often under-diagnosed, however, if it is suitably diagnosed, symptoms can be well treated by means of targeted drugs, such as modafinil to treat EDS, sodium oxybate for cataplexy, as well as EDS and disrupted nocturnal sleep, and tricyclic and newer antidepressants for cataplexy. Hallucinations and sleep paralysis can be treated with the same drugs used for cataplexy. Amphetamines and amphetamine-like stimulants are used less nowadays. Behavioral measures are also important and useful. The discovery of hypocretin deficiency in narcoleptic patients opens new perspectives for the development of newer therapeutic approaches for both EDS and cataplexy. Therapy for narcolepsy is chronic, hence symptomatic. However, the correct use of available drugs enables patients to gain a better quality of life, keeping the symptoms under control, which, mainly from a social point of view, are heavily disabling.

Management of narcolepsy

BACKGROUND

Narcolepsy is a rare chronic sleep disorder classically characterized by excessive daytime sleepiness. Other symptoms of the disease, including cataplexy, sleep paralysis, hypnagogic hallucinations and disturbed nocturnal sleep, may follow later. The disease can be incapacitating and frequently results in impaired psychosocial interaction. In the absence of a cure for narcolepsy, medical therapy is directed at symptom control.

OBJECTIVES

The aim of this study was to review the current approach to the treatment of narcolepsy.

METHODS

A search of three bibliographic databases (MEDLINE/PubMed, EMBASE and the Cochrane Library Database) was conducted from 1966 to January 2008 using the National Library of Medicine MeSH search terms narcolepsy and cataplexy. Relevant studies, case reports, review articles, editorials, short communications and chapters from selected textbooks were then extracted and manually cross-referenced.

RESULTS/CONCLUSIONS

Traditionally, stimulants have been used to improve the symptoms of excessive daytime sleepiness. However, the treatment of narcolepsy has evolved recently with the widespread use of newer drugs, including modafinil for daytime sleepiness, newer antidepressants for cataplexy and gamma-hydroxybutyrate (sodium oxybate) for both excessive daytime sleepiness and cataplexy.

Therapies for narcolepsy with or without cataplexy: evidence-based review

(1) Narcolepsy is a rare disorder of unknown aetiology characterized by excessive daytime sleepiness and typically associated with cataplexy. It is extremely incapacitating, and frequently results in impaired psychosocial functioning and reduced work performance. Currently there is no cure for narcolepsy, so treatment focuses on control of symptoms.(2) Although the sympathomimetic stimulants, such as amphetamines or methylphenidate, are effective in improving excessive daytime sleepiness in patients with narcolepsy, they have the potential for dependence, have sometimes disabling sympathomimetic side-effects and are associated with tolerance.(3) To date, there is clear evidence of the efficacy of modafinil, armodafinil and sodium oxybate in patients with narcolepsy. Modafinil and armodafinil improve excessive daytime sleepiness symptoms and have little abuse potential, but have no effect on cataplexy, so other drugs, such as antidepressants, are required to control cataplexy attacks.(4) Sodium oxybate improves both excessive daytime sleepiness and cataplexy. However, there is potential for abuse and possibly dependence.

Sodium oxybate: a review of its use in the management of narcolepsy

Sodium oxybate (Xyrem) is the sodium salt of the CNS depressant gamma-hydroxybutyric acid (GHB) and is therefore subject to prescription restrictions. It is approved in the US for the treatment of cataplexy and excessive daytime sleepiness (EDS) in patients with narcolepsy, and in the EU for the treatment of narcolepsy with cataplexy. Sodium oxybate is generally well tolerated and effective in the treatment of symptoms of narcolepsy with cataplexy. While its short half-life necessitates twice-nightly administration, it is highly effective in reducing the frequency of cataplexy, improving sleep architecture and reducing EDS in patients with narcolepsy. Sodium oxybate therefore offers a valuable alternative or addition to the use of TCAs, SSRIs and stimulants in the treatment of the symptoms of narcolepsy including cataplexy and EDS.

Narcolepsy with cataplexy

Narcolepsy with cataplexy is a disabling sleep disorder affecting 0.02% of adults worldwide. It is characterised by severe, irresistible daytime sleepiness and sudden loss of muscle tone (cataplexy), and can be associated with sleep-onset or sleep-offset paralysis and hallucinations, frequent movement and awakening during sleep, and weight gain. Sleep monitoring during night and day shows rapid sleep onset and abnormal, shortened rapid-eye-movement sleep latencies. The onset of narcolepsy with cataplexy is usually during teenage and young adulthood and persists throughout the lifetime. Pathophysiological studies have shown that the disease is caused by the early loss of neurons in the hypothalamus that produce hypocretin, a wakefulness-associated neurotransmitter present in cerebrospinal fluid. The cause of neural loss could be autoimmune since most patients have the HLA DQB1*0602 allele that predisposes individuals to the disorder. Treatment is with stimulant drugs to suppress daytime sleepiness, antidepressants for cataplexy, and gamma hydroxybutyrate for both symptoms. Because narcolepsy is an under-recognised disease, it is important that general practitioners and other primary health-care workers identify abnormal daytime sleepiness early.