A clinician's guide to recurrent isolated sleep paralysis

Morphological characteristics of cerebellum, pons and thalamus in Reccurent isolated sleep paralysis - A pilot study

Introduction

Recurrent isolated sleep paralysis (RISP) is a rapid eye movement sleep (REM) parasomnia, characterized by the loss of voluntary movements upon sleep onset and/or awakening with preserved consciousness. Evidence suggests microstructural changes of sleep in RISP, although the mechanism of this difference has not been clarified yet. Our research aims to identify potential morphological changes in the brain that can reflect these regulations.

Materials and methods

We recruited 10 participants with RISP (8 women; mean age 24.7 years; SD 2.4) and 10 healthy control subjects (w/o RISP; 3 women; mean age 26.3 years; SD 3.7). They underwent video-polysomnography (vPSG) and sleep macrostructure was analyzed. After that participants underwent magnetic resonance imaging (MRI) of the brain. We focused on 2-dimensional measurements of cerebellum, pons and thalamus. Statistical analysis was done in SPSS program. After analysis for normality we performed Mann-Whitney U test to compare our data.

Results

We did not find any statistically significant difference in sleep macrostructure between patients with and w/o RISP. No evidence of other sleep disturbances was found. 2-dimensional MRI measurements revealed statistically significant increase in cerebellar vermis height (p = 0.044) and antero-posterior diameter of midbrain-pons junction (p = 0.018) in RISP compared to w/o RISP.

Discussion

Our results suggest increase in size of cerebellum and midbrain-pons junction in RISP. This enlargement could be a sign of an over-compensatory mechanism to otherwise dysfunctional regulatory pathways. Further research should be done to measure these differences in time and with closer respect to the frequency of RISP episodes.

The Parasomnias

Parasomnias usually present in childhood and resolve spontaneously. The diagnosis of non-rapid eye movement-related parasomnias is mainly based on clinical descriptors and can be challenging. Rapid eye movement-related parasomnias may index an underlying psychiatric disorder. Even if benign, parasomnias can affect quality of life. Pediatricians and child psychiatrists should be familiarized with these sleep disorders and suggest adequate sleep hygiene, avoidance of sleep deprivation, and regular bedtimes even on weekends as the first step in management of these disorders. Clinicians should pursue the opportunity for tailoring treatments and consider referral to a sleep expert when indicated.

All-night spectral and microstate EEG analysis in patients with recurrent isolated sleep paralysis

The pathophysiology of recurrent isolated sleep paralysis (RISP) has yet to be fully clarified. Very little research has been performed on electroencephalographic (EEG) signatures outside RISP episodes. This study aimed to investigate whether sleep is disturbed even without the occurrence of a RISP episode and in a stage different than conventional REM sleep. 17 RISP patients and 17 control subjects underwent two consecutive full-night video-polysomnography recordings. Spectral analysis was performed on all sleep stages in the delta, theta, and alpha band. EEG microstate (MS) analysis was performed on the NREM 3 phase due to the overall high correlation of subject template maps with canonical templates. Spectral analysis showed a significantly higher power of theta band activity in REM and NREM 2 sleep stages in RISP patients. The observed rise was also apparent in other sleep stages. Conversely, alpha power showed a downward trend in RISP patients' deep sleep. MS maps similar to canonical topographies were obtained indicating the preservation of prototypical EEG generators in RISP patients. RISP patients showed significant differences in the temporal dynamics of MS, expressed by different transitions between MS C and D and between MS A and B. Both spectral analysis and MS characteristics showed abnormalities in the sleep of non-episodic RISP subjects. Our findings suggest that in order to understand the neurobiological background of RISP, there is a need to extend the analyzes beyond REM-related processes and highlight the value of EEG microstate dynamics as promising functional biomarkers of RISP.

A Dynamic Foundation: Aberrations of Sleep Architecture and Its Association With Clinical and Sub-clinical Psychopathology

This investigation centered on the hypnagogic and hypnopompic wake-sleep/sleep-wake transition states and the associated exploration of hypnagogic and hypnopompic experiences (HHEs), and sleep paralysis (SP) on psychiatric exacerbation and paradoxical masking. The study aims to discern causality by examining how these sleep-related experiences may contribute to the emergence or exacerbation of psychiatric and neurodegenerative conditions, particularly, pertaining to the clinical or sub-clinical demographic of Schizotypal Personality Disorder (STPD), Mood Disorders, Schizophrenia, Post-Traumatic Stress Disorder (PTSD), Generalized Anxiety Disorder (GAD), Narcolepsy, Panic Disorder, specific phobias, or heightened psychotic sensitivity. Methodologically, this study employed a comprehensive literature review, drawing from a range of studies across sleep medicine, psychiatry, and psychology, utilizing PubMed-indexed peer-reviewed scientific literature, sourcing from academic institutions, Google Scholar, and open-access publications. This interdisciplinary approach allowed for a nuanced and systematic understanding of the potential links between specific sleep-wake/wake-sleep aberrations and their masking or exacerbation of clinical/sub-clinical psychiatric symptomatology in this particular demographic. Insights gained from the outcome of this study hold promise for advancing understanding of the interrelationship between sleep neurobiology and psychiatric disorders. Additionally, the findings may inform targeted therapeutic interventions tailored to mitigate the impact of sleep-wake disruptions on vulnerable populations. The overarching objective is to bridge current gaps in knowledge, cultivating a more profound understanding with direct implications for both clinical practice and ongoing research endeavors. The study outcomes provide an intriguing understanding of the complex relationship between sleep neurobiology and psychiatric disorders, paving the way for targeted therapeutic interventions to alleviate the effects of sleep-wake disruptions, and addressing critical gaps in knowledge with direct implications for clinical practice and ongoing research.

Prevalence and Clinical Characteristics of Sleeping Paralysis: A Systematic Review and Meta-Analysis

Sleep paralysis (SP) is a mixed state of consciousness and sleep, combining features of rapid eye movement (REM) sleep with those of wakefulness. The exact cause of SP is unknown, and its prevalence varies among the studies. We aim to identify SP's global prevalence, the affected population's characteristics, and the SP's clinical picture. We searched three databases (PubMed, Scopus, and Web of Science (WoS)) using a unique search strategy to identify eligible studies. All observational studies identifying the prevalence or frequency of sleeping paralysis were included. No exclusions are made based on country, race, or questionnaire. The analysis was performed using the latest version of R software (R Core Team, Vienna, Austria). The analysis included 76 studies from 25 countries with 167,133 participants. The global prevalence of SP was 30% (95% CI (22%, 39%)). There were similar frequencies of isolated SP and SP (33%, 95% CI (26%, 42%), I2 = 97%, P <0.01; 31%, 95% CI (21%, 43%), I2 = 100%, P = 0, respectively). A subgroup analysis showed that the majority of those who experienced SP were psychiatric patients (35%, 95% CI (20%, 55%), I2 = 96%, P <0.01). The prevalence among non-psychiatric patients was among students (34%, 95% CI (23%, 47%), I2 = 100%, P = 0). Auditory and visual hallucinations were reported in 24.25% of patients. Around 4% had only visual hallucinations. Meta-regression showed no association between the frequency of SP and sex. Publication bias was detected among the included studies through visual inspection of funnel plot asymmetry. Our findings revealed that 30% of the population suffered from SP, especially psychiatric patients and students. The majority of SP cases lacked associated hallucinations, while a noteworthy proportion experienced combined visual and auditory hallucinations.

Isolated sleep paralysis: Clinical features, perception of aetiology, prevention and disruption strategies in a large international sample

STUDY OBJECTIVES

Isolated sleep paralysis is a benign but frightening condition characterised by a temporary inability to move at sleep onset or upon awakening. Despite the prevalence of this condition, little is known concerning its clinical features, associated demographic characteristics, and prevention as well as disruption strategies.

METHODS

An online cross-sectional study was conducted. The sample comprised 3523 participants who had reported at least one lifetime episode of ISP and 3288 participants without a lifetime episode. Participants answered a survey including questions about sleep quality, sleep paralysis, and sleep paralysis prevention/disruption techniques.

RESULTS

A total of 6811 participants were investigated (mean age = 46.9, SD = 15.4, age range = 18-89, 66.1% female). Those who reported experiencing ISP at least once during their lives reported longer sleep onset latencies, shorter sleep duration, and greater insomnia symptoms. Females (vs. male) and younger (vs. older) participants were more likely to experience ISP. Significant fear during episodes was reported by 76.0% of the participants. Most people (63.3%) who experienced ISP believed it to be caused by 'something in the brain'. A minority endorsed supernatural causes (7.1%). Five prevention strategies (e.g., changing sleep position, adjusting sleep patterns) with at least 60.0% effectiveness, and five disruption strategies (e.g., physical/bodily action, making noise) with varying degrees of effectiveness (ranging from 29.5 to 61.8) were identified through open-ended responses.

CONCLUSIONS

ISP is associated with shorter sleep duration, longer sleep onset latency, and greater insomnia symptoms. The multiple prevention and disruption techniques identified in this study support existing treatment approaches and may inform subsequent treatment development. Implications for current diagnostic criteria are discussed.

Spontaneous and induced out-of-body experiences during sleep paralysis: Emotions, "AURA" recognition, and clinical implications

Sleep paralysis is characterized by the incapacity to perform voluntary movements during sleep/wake transitions, and could bring great discomfort. During sleep paralysis, out-of-body experiences can occur. Out-of-body experiences refers to the sensation of being outside of the physical body and perceiving the world from this outside perspective; however, they are pleasant in comparison with other sleep paralysis hallucinations. Lucid dreams are dreams in which a subject becomes aware of being dreaming while the dream occurs. Here, we designed an online survey to study the predominant and specific emotions during sleep paralysis and/or out-of-body experience events as well as the somatosensory perceptions that preceded their occurrence. The sample (N = 329) was divided into experimental groups depending on the presence/absence of out-of-body experiences, capacity to induce (or not) out-of-body experiences, and perception/no-perception of the sleep paralysis. We showed that more positive emotions were associated with out-of-body experiences and more negative emotions were associated with sleep paralysis episodes, and for those who claim the ability to induce out-of-body experiences, positive emotions were more frequent in their episodes. We found that subjects perceived auditory, tactile and visual sensations before sleep paralysis episodes, and we proposed that these could be an "aura" of sleep paralysis. Furthermore, subjects that had out-of-body experiences but had never felt the sleep paralysis, perceived tactile and visual sensations to the same extent as subjects with out-of-body experiences that felt the sleep paralysis. Therefore, we proposed that the "aura" recognition could be used under controlled conditions for out-of-body experiences induction in patients with sleep paralysis to diminish the negative symptoms associated with sleep paralysis episodes.

The associations between paranormal beliefs and sleep variables

Previous studies have found significant associations between paranormal beliefs and sleep variables. However, these have been conducted on a small scale and are limited in the number of sleep variables investigated. This study aims to fill a gap in the literature by investigating paranormal beliefs in relation to a wide range of sleep variables in a large sample. Participants (N = 8853) completed a survey initiated by the BBC Focus Magazine. They reported on their demographics, sleep disturbances and paranormal beliefs. Poorer subjective sleep quality (lower sleep efficiency, longer sleep latency, shorter sleep duration and increased insomnia symptoms) was associated with greater endorsement of belief in: (1) the soul living on after death; (2) the existence of ghosts; (3) demons; (4) an ability for some people to communicate with the dead; (5) near-death experiences are evidence for life after death; and (6) aliens have visited earth. In addition, episodes of exploding head syndrome and isolated sleep paralysis were associated with the belief that aliens have visited earth. Isolated sleep paralysis was also associated with the belief that near-death experiences are evidence for life after death. Findings obtained here indicate that there are associations between beliefs in the paranormal and various sleep variables. This information could potentially better equip us to support sleep via psychoeducation. Mechanisms underlying these associations are likely complex, and need to be further explored to fully understand why people sometimes report "things that go bump in the night".

Sleep-related motor disorders

Sleep-related motor disorders include non-rapid-eye movement (NREM) sleep parasomnias, rapid-eye movement (REM), sleep parasomnias including REM sleep behavior disorder (RBD), isolated motor phenomena in sleep, and periodic limb movement disorder. Restless legs syndrome (RLS) occurs while awake but is closely related to sleep and has a circadian pattern. The pontine sublaterodorsal tegmental nucleus has an important role in aligning motor control with sleep states, and dysfunction in this region can explain motor activities including cataplexy and loss of REM atonia seen in REM sleep behavior disorder. This chapter begins with a review of motor control in sleep. The rest of the chapter summarizes the clinical presentation, epidemiology, differential and treatment of NREM, REM, and isolated sleep-related motor disorders as well as restless legs syndrome.

Detection of Sleep Paralysis by using IoT Based Device and Its Relationship Between Sleep Paralysis And Sleep Quality

When a person wakes up in the middle of the night, they are paralyzed. Despite the fact that most episodes are associated with extreme terror and some might cause clinically significant suffering, little is understood about the experience. This study will analyze existing research on the relationship between sleep paralyses and sleep in general. Many studies have connected poor sleep quality to an increased risk of sleep paralysis. Awake yet unable to act, sleep paralysis occurs. This might happen between awake and sleeping. The problem is approached in three steps: Data collection, data storage, calculation and machine learning prediction of sleep paralysis. The data came from the Smart Device. The dataset has several (independent) and dependent variables (Outcome). This device has been put to the test. Each exam has its own set of features and predicted outcomes. To assess the system's validity, we executed a posture recognition accuracy test. The device was hidden on top of the bed. The controller is in charge of measurement and data collection. Experiments were conducted by collecting pressure data from a patient lying down. The person acted out his sleeping positions on a mat for a while. Machine learning has been used to predict sleep paralysis. By comparing sleep postures to the outcome, we were able to show the link between sleep qualities and sleep paralysis. Machine learning approaches have been used to predict sleep paralysis. Comparing sleeping positions with the results showed the link between sleep quality and sleep paralysis. Sleep paralysis correlates with poor sleep quality. The Random Forest model has the highest accuracy of 91.9 percent in predicting sleep paralysis in the given dataset. SVM with Linear Kernel was 80.49 percent accurate, RBF was 42.68 percent, and Polynomial was 47.56 percent. The accuracy of logistic regression was 76.83 percent. KNN had a dismal performance of 60.98%. Decision Trees and Gradient Boosting both fared well at 85.37 percent.

Successful treatment of sleep paralysis with the Sleep Position Trainer: a case report

Sleep paralysis is a period of paralysis at either sleep onset or upon awakening and is often accompanied by terrifying hallucinations. We report a case of a 32-year-old healthy men with a history of mild positional obstructive sleep apnea and sleep paralysis. The positional sleep apnea was successfully treated with the Sleep Position Trainer. Remarkably, he did no longer experience episodes of sleep paralysis since using the Sleep Position Trainer. This case highlights a possible elegant noninvasive long-term solution for the treatment of sleep paralysis.

CITATION

Cui N, van Looij MA, Kasius KM. Successful treatment of sleep paralysis with the Sleep Position Trainer: a case report. J Clin Sleep Med. 2022;18(9):2317-2319.

Sleep terrors-A parental nightmare

Sleep terrors (STs) are sleep disorders characterized by abrupt arousal from sleep with autonomic hyperactivity and inappropriate behavior. Though a common condition in childhood that usually affects children between 4 and 12 years of age, STs, however, may be present even in adulthood. The exact etiology of STs is not known yet, however, several hypotheses have been proposed over the years, identifying some potential genetic, neurodevelopmental, or other causes. Nevertheless, a useful pathophysiological model identified a common cascade of predisposing, priming, and precipitating factors, which could help to explain and sometimes prevent STs. Establishing a correct diagnosis is mandatory for appropriate management, as several conditions (such as other parasomnias or nocturnal seizures) may mimic STs. Furthermore, we also described some conditions which can be comorbid to STs, like some medical or psychological disorders. A number of treatment options have been proposed, ranging from only sleep hygiene practices to pharmacological therapies; we reviewed some of the most prominent ones. In spite of the fact that STs have long been considered benign disorders, which tend to reduce spontaneously over the years, they may have unexpected consequences on the child but also on the caregivers.

Characteristics of Sleep Paralysis and Its Association with Anxiety Symptoms, Perceived Stress, PTSD, and Other Variables Related to Lifestyle in Selected High Stress Exposed Professions

Sleep paralysis (SP) is a hypnagogic or hypnopompic state associated with the inability to move while conscious. Recurrent isolated sleep paralysis (RISP) is a type of REM parasomnia. Individuals experiencing anxiety disorders, PTSD, exposure to chronic stress, or shift work are at risk of developing this sleep disorder. This study aimed to assess: (1) the prevalence, frequency, and symptomatology of SP, and (2) the impact of the severity of anxiety symptoms, perceived stress, and lifestyle mode variables on the frequency and severity of SP in four professional groups at high risk of SP (n = 844): nurses and midwives (n = 172), policemen (n = 174), teachers (n = 107), and a group of mixed professions—“other professions” (n = 391). The study used a battery of online questionnaires: the Sociodemographic and Health Status Questionnaire, the SP-EPQ, the PCL -5, the STAI-T, the PSWQ and the PSS-10. The prevalence of SP was the lowest among policemen (15.5%) and the highest in the group of “other professions” (39.4%). The association of SP with symptoms of PTSD and anxiety was confirmed in the group of nurses and “other professions”. Among other factors modulating the incidence and severity of SP were: age, BMI, smoking, alcohol consumption, sleep duration, and perceived stress. This study indicates that there exist links between SP and psychological and lifestyle factors, suggesting a complex etiology for this sleep disorder. Due to the high prevalence of SP in the studied groups of occupations, further research is necessary to develop preventive and therapeutic methods for SP.

Risk factors of sleep paralysis in a population of Polish students

BACKGROUND

Sleep paralysis (SP) is a transitional dissociative state associated with the REM sleep phase that affects approximately 28.3% of the student population during their lifetime. The reasons for the high prevalence of SP in the student population are not entirely clear. Research indicates possible influencing factors such as the intensification of anxiety symptoms, a tendency to worry, the presence of PTSD symptoms, and behavioral factors such as the consumption of psychoactive substances (caffeine, alcohol, nicotine), sleep deprivations and poor sleep hygiene. The study aimed to assess the prevalence of SP and determine the risk factors for the occurrence of SP in the population of Polish students.

METHODS

The study used a battery online consisting of a set of questionnaires 1) a personal questionnaire, 2) the SP-EPQ, 3) the PCL -5, 4) the STAI-T, 5) the PSWQ. The questionnaire was sent via Facebook to 4500 randomly selected students from different universities in Poland. The questionnaire was completed by 2598 students. To unify the participant sample, people over 35 were excluded from the study (45 students). Ultimately, data from 2553 students were analyzed.

RESULTS

A total of 33.14% of individuals experienced at least one episode of SP in their lives. The highest odds ratio for SP was associated with: the presence of three or more health problems (OR: 2.3; p = 0.002), the presence of any mental disorder (OR: 1.77; p = 0.002), including mood disorders (OR: 2.07; p = 0.002), suffering from at least one somatic disease (OR: 1.34; p = 0.002), a high level of anxiety as a constant personality trait (OR: 1.20; p = 0.035) and smoking (OR: 1.48; p = 0.0002), alcohol consumption (OR: 1.52; p < 0.0001), physical activity (OR: 1.31; p = 0.001).

CONCLUSIONS

The results of our research indicate that a large proportion of students experienced isolated sleep paralysis. Mental and somatic health problems and lifestyle factors were found to predispose individuals to this disorder. Due to the numerous risk factors for SP, it is necessary to conduct additional research to confirm the impact of these factors and to investigate the mechanisms of their influence on SP.

Post-traumatic stress disorder, suggestibility, and dissociation related to alleged alien abductions

OBJECTIVES

Thousands of people throughout the world are convinced that they have been abducted by aliens. We aimed to assess the emotional reaction to such an implausible event and propose some explanations alternative to severe psychopathology.

METHODS

A total of 19 individuals who reported memories of having been abducted by aliens were compared to a control group of 32 participants. We employed a battery of tests measuring post-traumatic stress disorder, suggestibility, and dissociation within all participants.

RESULTS

The abductee group showed higher scores in measures of post-traumatic stress disorders and dissociation, but lower in suggestibility. Nevertheless, these differences were statistically significant only in suggestibility.

CONCLUSIONS

The emotional reaction to memories of an implausible experience can be similar to an individual's response to a genuinely traumatic event. Dissociation might be involved in the clarification of some cases. Explanations alternative to psychosis for these testimonies are proposed.

Sleep Paralysis among Professional Firefighters and a Possible Association with PTSD-Online Survey-Based Study

The prevalence of sleep paralysis (SP) is estimated at approximately 7.6% of the world’s general population. One of the strongest factors in the onset of SP is PTSD, which is often found among professional firefighters. Our study aimed to assess in the professional firefighter population (n = 831) (1) the prevalence of SP, (2) the relationship between SP and PTSD and (3) the relationship between SP and other factors: the severity of the stress felt, individual tendency to feel anxious and worried and lifestyle variables. The incidence of SP in the study group was 8.7%. The high probability of PTSD was found in 15.04% of subjects and its presence was associated with 1.86 times the odds of developing SP [OR = 1.86 (95% CI: 1.04–3.33); p = 0.04]. Officers who experienced at least 1 SP during their lifetime had significantly higher results in the scales: PCL-5, STAI-T, PSWQ. The number of SP episodes was positively correlated with the severity of symptoms measured by the PCL-5, PSS-10, STAI and PSWQ questionnaires. Further research is needed to assess the importance of SP among the firefighter population in the context of mental and somatic health and to specify methods of preventing SP episodes.

Objective REM sleep characteristics of recurrent isolated sleep paralysis: a case-control study

STUDY OBJECTIVES

Recurrent isolated sleep paralysis (RISP) is a rapid eye movement (REM) parasomnia characterized by a dissociative state with characteristics of REM sleep and wakefulness. Pathophysiology has not yet been clarified and very little research has been performed using objective polysomnographic measures with inconsistent results. The main aim of our study was to find whether higher REM sleep fragmentation is consistent with the theory of state dissociation or whether signs of dissociation can be detected by spectral analysis.

METHODS

Nineteen participants in the RISP group and 19 age- and gender-matched participants in the control group underwent two consecutive full-night video-polysomnography recordings with 19-channel electroencephalography. Apart from sleep macrostructure, other REM sleep characteristics such as REM arousal index, percentage of wakefulness and stage shifts within REM sleep period were analyzed, as well as power spectral analysis during REM sleep.

RESULTS

No difference was found in the macrostructural parameters of REM sleep (percentage of REM sleep and REM latency). Similarly, no significant difference was detected in REM sleep fragmentation (assessed by REM sleep arousal index, percentage of wakefulness and stage shifts within REM sleep). Power spectral analysis showed higher bifrontal beta activity in the RISP group during REM sleep.

CONCLUSIONS

The results showed an underlying persistent trait of higher cortical activity that may predispose patients with SP to be more likely to experience recurrent episodes, without any apparent macrostructural features including higher REM sleep fragmentation.

The Parasomnias

Parasomnias usually present in childhood and resolve spontaneously. The diagnosis of non-rapid eye movement-related parasomnias is mainly based on clinical descriptors and can be challenging. Rapid eye movement-related parasomnias may index an underlying psychiatric disorder. Even if benign, parasomnias can affect quality of life. Pediatricians and child psychiatrists should be familiarized with these sleep disorders and suggest adequate sleep hygiene, avoidance of sleep deprivation, and regular bedtimes even on weekends as the first step in management of these disorders. Clinicians should pursue the opportunity for tailoring treatments and consider referral to a sleep expert when indicated.

Recognizing the Symptom Spectrum of Narcolepsy to Improve Timely Diagnosis: A Narrative Review

Narcolepsy is a chronic sleep disorder with a strong negative impact on quality of life, especially when untreated. Diagnostic delay is a persistent problem, with obvious detrimental effects on patients. A diagnosis of narcolepsy may be delayed because of its broad symptom presentation which is much more encompassing than the classical "tetrad" of sleepiness, cataplexy, hallucinations, and sleep paralysis. Furthermore, symptoms can vary over time. Presentation of symptoms can also be markedly different between children and adults. Finally, common sleep-related comorbidities increase the risk of narcolepsy being masked by overlapping symptoms or treatment. In this review, we provide a detailed description of the broad and dynamic symptom spectrum of narcolepsy, with specific attention to the different manifestations in both adults and children. The overarching goal is to help not only sleep specialists, but general practitioners, pediatricians, and other caregivers with early recognition and prompt diagnosis of this severe but treatable disorder.

Differentiating Oneiric Stupor in Agrypnia Excitata From Dreaming Disorders

Oneiric Stupor (OS) in Agrypnia Excitata represents a peculiar condition characterized by the recurrence of stereotyped gestures such as mimicking daily-life activities associated with the reporting of a dream mentation consisting in a single oneiric scene. It arises in the context of a completely disorganized sleep structure lacking any physiological cyclic organization, thus, going beyond the concept of abnormal dream. However, a proper differential diagnosis of OS, in the complex world of the “disorders of dreaming” can become quite challenging. The aim of this review is to provide useful clinical and videopolygraphic data on OS to differentiate it from other dreaming disorders. Each entity will be clinically evaluated among the areas of dream mentation and abnormal sleep behaviors and its polygraphic features will be analyzed and distinguished from OS.

Could sleep paralysis be pleasant?

Sleep paralysis is an inability to move at sleep onset or upon awakening. It is often a distressing experience that can be associated with significant clinical consequences. Few studies have focussed on pleasant sleep paralysis episodes. The present study aimed to determine the relative prevalence of pleasant episodes of sleep paralysis as well as variables that may make them more likely to occur. Participants (N = 172) with recurrent episodes of sleep paralysis completed a battery of questionnaires investigating sleep paralysis episodes, trauma symptoms, life satisfaction, and Big Five personality traits. Pleasant sleep paralysis was found to be a fairly common experience (i.e. 23%). Episodes were emotionally complex, with pleasant episodes often involving some admixture of fear. In terms of hallucinations, pleasant episodes were more likely to involve vestibular-motor sensations (i.e. illusory body movements) and some individuals reported an ability to induce these hallucinations. Contrary to expectation, neither lower trauma symptomatology nor higher levels of reported life satisfaction predicted pleasant sleep paralysis. However, the ability to lucid dream and higher levels of trait openness to new experiences appeared to make pleasant episodes more likely. Clinical implications are discussed.

The Neurology of Death and the Dying Brain: A Pictorial Essay

As neurologists earn their living with the preservation and restoration of brain function, they are also well-positioned to address the science behind the transition from life to death. This essay in pictures highlights areas of neurological expertise needed for brain death determination; shows pitfalls to avoid during the clinical examination and interpretation of confirmatory laboratory tests in brain death protocols; illustrates the great variability of brain death legislations around the world; discusses arguments for the implementation of donation after circulatory death (DCD); points to unresolved questions related to DCD and the time between cardiac standstill and organ procurement (“hands-off period”); provides an overview of the epidemiology and semiology of near-death experiences, including their importance for religion, literature, and the visual arts; suggests biological mechanisms for near-death experiences such as dysfunction of temporoparietal cortex, N-methyl-D-aspartate receptor antagonism, migraine aura, and rapid eye movement sleep; hypothesizes that thanatosis (aka. death-feigning, a common behavioral trait in the animal kingdom) represents the evolutionary origin of near-death experiences; and speculates about the future implications of recent attempts of brain resuscitation in an animal model. The aim is to provide the reader with a thorough understanding that the boundaries within the neurology of death and the dying brain are being pushed just like everywhere else in the clinical neurosciences.

Update on nonpharmacological interventions in parasomnias

Parasomnias are abnormal behaviors that occur during sleep and can be associated, in particular during adulthood, with impaired sleep quality, daytime dysfunction, and occasionally with violent and harmful nocturnal behaviors. In these cases, therapies are often considered. Longterm pharmacological treatments are not always well tolerated and often have limited efficacy. Therefore, behavioral approaches remain an important treatment option for several types of parasomnias. However, the evidence-based approaches are limited. In the current review, we highlight results from various nonpharmacological techniques on different types of parasomnias and provide a glimpse into the future of nonpharmacological treatments in this field.

RECURRENT SLEEP PARALYSIS - FEAR OF SLEEPING

Objective:

To report a case of recurrent isolated sleep paralysis (RISP), a benign parasomnia with worrisome and frightening sleep paralysis episodes.

Case

description: We describe a case of RISP in a sixteen-year-old girl who seeks medical attention for anxiety symptoms. The sleep paralysis and associated auditory and tactile hallucinations began three years before with worsening in the last year, causing fear of sleeping. The episodes were intensely frightening causing negative impact in patient’s sleep, school performance and social function. Medical conditions were excluded, and she started treatment with a selective serotonin reuptake inhibitor with complete resolution of symptoms.

Comments:

Sleep complaints are often devalued. Therefore, clinicians should actively ask their patients about their sleep during health assessment.

HLA and sleep parameter associations in post-H1N1 narcolepsy type 1 patients and first-degree relatives

Study Objectives

To explore HLA (human leukocyte antigen) in post-H1N1 narcolepsy type 1 patients (NT1), first-degree relatives and healthy controls, and assess HLA associations with clinical and sleep parameters in patients and first-degree relatives.

Methods

Ninety post-H1N1 NT1 patients and 202 of their first-degree relatives were HLA-genotyped (next generation sequencing) and phenotyped (semistructured interviews, Stanford Sleep Questionnaire, polysomnography, and multiple sleep latency test). HLA allele distributions were compared between DQB1*06:02-heterozygous individuals (77 patients, 59 parents, 1230 controls). A subsample (74 patients, 114 relatives) was investigated for associations between HLA-loci and continuous sleep variables using logistic regression. Identified candidate HLA-loci were explored for HLA allele associations with hypnagogic hallucinations and sleep paralysis in 90 patients, and patient allele findings were checked for similar associations in 202 relatives.

Results

DQB1*06:02 heterozygous post-H1N1 NT1 patients (84.4% H1N1-vaccinated) showed several significant HLA associations similar to those reported previously in samples of mainly sporadic NT1, i.e. DQB1*03:01, DRB1*04:01, DRB1*04:02, DRB1*04:07, DRB1*11:04, A*25:01, B*35:03, and B*51:01, and novel associations, i.e. B*14:02, C*01:02, and C*07:01. Parents HLA alleles did not deviate significantly from controls. The HLA-C locus was associated with sleep parameters in patients and relatives. In patients C*02:02 seems to be associated with protective effects against sleep paralysis and hypnagogic hallucinations.

Conclusions

Our findings of similar risk/protective HLA-alleles in post-H1N1 as in previous studies of mainly sporadic narcolepsy support similar disease mechanisms. We also report novel allelic associations. Associations between HLA-C and sleep parameters were seen independent of NT1 diagnosis, supporting involvement of HLA-C in sleep subphenotypes.

Culturally sensitive assessment of anxious-depressive distress in the Cambodian population: Avoiding category truncation

In a large national survey in Cambodia (N = 2689), the present study investigated the prominence of certain culturally salient symptoms and syndromes in the general population and among those with anxious-depressive distress (as determined by the Hopkins Symptom Checklist-25, or HSCL). Using an abbreviated Cambodian Symptom and Syndrome Addendum (CSSA), we found that the CSSA complaints were particularly elevated among those with anxious-depressive distress. Those with anxious-depressive distress had statistically greater mean scores on all the CSSA items as well as severity of endorsement analyzed by percentage: among those with HSCL caseness, 75.3% were bothered "quite a bit" or "extremely" by "thinking a lot" (vs. 27.5% without caseness); 53.8% were bothered by "standing up and feeling dizzy" (vs. 13.8%); and 45.6% by blurry vision (vs. 16.8%). In a logistic regression analysis to predict anxious-depressive distress, 51% of the variance was accounted for by five predictors: "weak heart," "thinking a lot," dizziness, "khyâl hitting up from the stomach," and sleep paralysis. Using ROC analysis, a cut-off score of 1.81 on the CSSA was optimal as a screener to indicate anxious-depressive distress, giving a sensitivity of 0.86. The study results suggest that to avoid category truncation (i.e., the omission of key complaints that are part of an assessed distress domain) when profiling anxious-depressive distress among Cambodia population that items other than those in standard psychopathology measures should be assessed such as "thinking a lot," "weak heart," "blurry vision," and "dizziness upon standing up."

What do we know about sleep paralysis?

Introduction: Sleep paralysis (SP) is a condition that widely occurs among people all over the world. It has been known for thousands of years and is rooted in the culture of many countries. It arouses strong emotions, though still little is known about it. The clinical picture of the disorder can be very diverse. It is often accompanied by hypnopompic and hypnagogic hallucinations, somatic complaints and the feeling of intense anxiety. A feeling of paralysis in the body with inhibited consciousness is always observed with the experience. SP pathophysiology is not fully understood, however, most theories explaining this phenomenon are based on the assumption that it results from dysfunctional overlap of REM sleep and wakefulness. It is experienced by healthy people, but it is more often associated with somatic and mental disorders, which is why it is becoming an object of interest for researchers.

Aim: The aim of this work is to present the most important information about the disorder known as sleep paralysis - its history, cultural context, pathophysiology, prevalence, symptomatology, coexistence with other somatic and mental disorders as well as diagnostics and available forms of prevention and treatment.

Materials and methodology: The available literature was reviewed using the Google Scholar bibliographic databases searching the following keywords: sleep paralysis, REM sleep parasomnias, sleep disorder, night terrors and time descriptors: 1980-2018.

Results 1. Sleep paralysis has already been described in antiquity, and interpretations related to its occurrence are largely dependent on culture and beliefs.

2. Symptomatology of the disorder is very diverse: both mental and somatic symptoms are present.

3. The pathophysiology of the disorder has not been fully explained. The basis of most theories regarding sleep paralysis is the assumption that it results from the dysfunctional overlap of REM sleep and wakefulness.

4. The prevalence of SP at least once in a lifetime is 7.6% in the general population, although it is estimated that it is much more frequent in people with various mental and somatic disorders.

5. Treatment of SP is associated with a change in lifestyle and the use of pharmacotherapy and psychotherapy.

The neuropharmacology of sleep paralysis hallucinations: serotonin 2A activation and a novel therapeutic drug

Sleep paralysis is a state of involuntary immobility occurring at sleep onset or offset, often accompanied by uncanny "ghost-like" hallucinations and extreme fear reactions. I provide here a neuropharmacological account for these hallucinatory experiences by evoking the role of the serotonin 2A receptor (5-HT2AR). Research has shown that 5-HT2AR activation can induce visual hallucinations, "mystical" subjective states, and out-of-body experiences (OBEs), and modulate fear circuits. Hallucinatory experiences triggered by serotonin-serotonergic ("pseudo") hallucinations, induced by hallucinogenic drugs-tend to be "dream-like" with the experiencer having insight ("meta-awareness") that he is hallucinating, unlike dopaminergic ("psychotic" and "life-like") hallucinations where such insight is lost. Indeed, hallucinatory experiences during sleep paralysis have the classic features of serotonergic hallucinations, and are strikingly similar to perceptual and subjective states induced by hallucinogenic drugs (e.g., lysergic acid diethylamide [LSD] and psilocybin), i.e., they entail visual hallucinations, mystical experiences, OBEs, and extreme fear reactions. I propose a possible mechanism whereby serotonin could be functionally implicated in generating sleep paralysis hallucinations and fear reactions through 5-HT2AR activity. Moreover, I speculate on the role of 5-HT2C receptors vis-à-vis anxiety and panic during sleep paralysis, and the orbitofrontal cortex-rich with 5-HT2A receptors-in influencing visual pathways during sleep paralysis, and, in effect, hallucinations. Finally, I propose, for the first time, a drug to target sleep paralysis hallucinations and fear reactions, namely the selective 5-HT2AR inverse agonist, pimavanserin. This account implicates gene HTR2A on chromosome 13q as the underlying cause of sleep paralysis hallucinations and could be explored using positron emission tomography.

Culturally Sensitive Assessment of Anxious-Depressive Distress in Vietnam: Avoiding Category Truncation

The present study investigated what complaints are prominent in psychologically distressed Vietnamese in Vietnam beyond standard symptoms assessed by Western diagnostic instruments for anxiety and depression. To form the initial Vietnamese Symptom and Cultural Syndrome Addendum (VN SSA), we reviewed the literature, consulted experts, and conducted focus groups. The preliminary VN SSA was then used in a general survey (N = 1004) of five provinces in Vietnam. We found that the VN SSA items were highly and significantly correlated with a measure of anxious-depressive psychopathology (a composite measure of the General Anxiety Disorder-7; Posttraumatic Diagnostic Scale; and Patient Health Questionnaire-9). The VN SSA item most highly correlated to anxious-depressive psychopathology was "thinking a lot" ( r = .54), reported by 15.8% of the sample. Many other symptoms in the addendum also were prominent, such as orthostatic dizziness (i.e., dizziness upon standing up; r = .41), reported by 22.9% of the sample. By way of comparison, somatic complaints more typically assessed to profile Western anxious-depressive distress, such as palpitations, were less prominent, as evidenced by being less strongly correlated to Western psychiatric symptoms and being less frequent (e.g., palpitations: r = .31, 7.1% of the sample). Study results suggest that to avoid category truncation when profiling anxious-depressive distress among Vietnamese that items other than those in standard psychopathology measures should also be assessed.

Relationships between sleep paralysis and sleep quality: current insights

Sleep paralysis is the unusual experience of waking up in the night without the ability to move. Currently little is known about the experience, despite the fact that the vast majority of episodes are associated with extreme fear and in a minority of cases can lead to clinically significant levels of distress. The aim of this work was to review the existing literature pertaining to the relationship sleep paralysis has to sleep more generally, measured both with subjective questionnaires and objective laboratory recordings. In terms of subjective sleep variables, worse sleep quality has been found in multiple studies to be associated with increased odds of sleep paralysis occurrence. In addition, insomnia symptoms (but not a diagnosed insomnia disorder) have also been found to predict sleep paralysis. Associations between sleep paralysis and other unusual and/or threatening sleep experiences such as nightmares, exploding head syndrome, and lucid dreaming have been reported. In terms of objective measurements, the limited literature to date shows sleep paralysis to be a "mixed" state of consciousness, combining elements of rapid eye movement sleep with elements of wakefulness. Future research needs to focus on longitudinal designs to disentangle the direction of effects and more typically employ a broader assessment of sleep paralysis that better captures associated features such as hallucinations, fear, and distress.

Sleep-related movement disorders and disturbances of motor control

PURPOSE OF REVIEW

Review of the literature pertaining to clinical presentation, classification, epidemiology, pathophysiology, diagnosis, and treatment of sleep-related movement disorders and disturbances of motor control.

RECENT FINDINGS

Sleep-related movement disorders and disturbances of motor control are typically characterized by positive motor symptoms and are often associated with sleep disturbances and consequent daytime symptoms (e.g. fatigue, sleepiness). They often represent the first or main manifestation of underlying disorders of the central nervous system, which require specific work-up and treatment. Diverse and often combined cause factors have been identified. Although recent data provide some evidence regarding abnormal activation and/or disinhibition of motor circuits during sleep, for the majority of these disorders the pathogenetic mechanisms remain speculative. The differential diagnosis is sometimes difficult and misdiagnoses are not infrequent. The diagnosis is based on clinical and video-polysomnographic findings. Treatment of sleep-related motor disturbances with few exceptions (e.g. restless legs/limbs syndrome) are based mainly on anecdotal reports or small series.

SUMMARY

More state-of-the-art studies on the cause, pathophysiology, and treatment of sleep-related movement disorders and disturbances of motor control are needed.

Prevalence Rates of the Incubus Phenomenon: A Systematic Review and Meta-Analysis

BACKGROUND

The incubus phenomenon is a paroxysmal sleep-related disorder characterized by compound hallucinations experienced during brief phases of (apparent) wakefulness. The condition has an almost stereotypical presentation, characterized by a hallucinated being that exerts pressure on the thorax, meanwhile carrying out aggressive and/or sexual acts. It tends to be accompanied by sleep paralysis, anxiety, vegetative symptoms, and feelings of suffocation. Its prevalence rate is unknown since, in prior analyses, cases of recurrent isolated sleep paralysis with/without an incubus phenomenon have been pooled together. This is unfortunate, since the incubus phenomenon has a much greater clinical relevance than isolated sleep paralysis.

METHODS

PubMed, Embase, and PsycINFO were searched for prevalence studies of the incubus phenomenon, and a meta-analysis was performed.

RESULTS

Of the 1,437 unique records, 13 met the inclusion criteria, reporting on 14 (k) independent prevalence estimates (total N = 6,079). The pooled lifetime prevalence rate of the incubus phenomenon was 0.19 [95% confidence interval (CI) = 0.14-0.25, k = 14, N = 6,079] with heterogeneous estimates over different samples. In selected samples (e.g., patients with a psychiatric disorder, refugees, and students), prevalence rates were nearly four times higher (0.41, 95% CI = 0.25-0.56, k = 4, n = 1,275) than in the random samples (0.11, 95% CI = 0.08-0.14, k = 10, n = 4,804). This difference was significant (P < 0.001).

CONCLUSION

This review and meta-analysis yielded a lifetime prevalence of the incubus phenomenon in the general population of 0.11 and, in selected samples, of 0.41. This is slightly higher than the prevalence rates in previous analyses that included cases of recurrent isolated sleep paralysis without an incubus phenomenon. Based on the condition's robust clinical presentation and the relatively high prevalence rates, we advocate inclusion of the incubus phenomenon as a diagnostic category in major classifications such as the International Classification of Diseases and Related Health Problems and the Diagnostic and Statistical Manual of Mental Disorders. Recommendations are also made for clinical practice and future research.