Disorders of Arousal


Disorders of Arousal




Introduction


Parasomnias represent a broad group of sleep disorders that are defined as undesirable phenomena occurring predominantly during sleep, first described by Broughton.1 These sleep disorders are of great interest to sleep specialists, primary care providers, and patients (and their parents) because this group comprises some of the most common and bizarre sleep problems seen in children. Disorders of arousal are the most common of the parasomnias seen in children. Disorders of arousal are defined similarly by the Diagnostic and Statistical Manual of Mental Disorders, 5th edition (DSM-V)2 and the International Classification of Sleep Disorders, 3rd edition (ICSD-3).3 Both classification schema define subtypes: sleepwalking, confusional arousals and sleep terrors.



Clinical Description


The clinical features common to most children experiencing any of the disorders of arousal include the timing during the nighttime sleep cycle, misperception of and unresponsiveness to the environment, automatic behavior, a high arousal threshold, varying levels of autonomic arousal, and (on waking after an event or in the morning) variable retrograde amnesia. The disorders of arousal typically begin abruptly at the transition from the first period of the deepest phase of non-REM (NREM) sleep (slow-wave sleep, stage N3) of the night (Figures 39.1 and 39.2), which accounts for the typical timing 60 to 90 minutes after sleep onset at the end of the first sleep cycle. The duration of each event can vary from less than 1 minute to over 30 minutes. In most cases, the arousal terminates with the child returning to sleep without ever fully awakening. Although only a single event usually occurs on a given night, some children may have multiple ones. When there are multiple events, they often will recur at 60- to 90-minute intervals during the night, corresponding to subsequent transitions out of slow-wave sleep at the end of each subsequent ultradian sleep cycle, though the arousals may occur at any time during the night. Successive events on the same night tend to be progressively milder.




Although the clinical manifestations of the disorders of arousal occur along a spectrum, for ease of description and to establish a common nomenclature, the DSM-V and ICSD-3 have divided the spectrum of arousal disorders into three distinct entities: sleepwalking, confusional arousals, and sleep terrors; however, in the pediatric literature, no clear distinction is generally made between confusional arousals and sleep terrors. Confusional arousals are much more common in children, especially in young children. Sleep terrors occur much less frequently, are more violent, and typically occur in older children and adolescents. At the mildest end of the clinical spectrum, a child will simply awaken from sleep, sit up in bed, look around briefly, lie back down, and return to sleep. These arousals are rarely noticed unless the child sleeps with a parent. This type of arousal is usually not characterized as a problem by parents and is seldom brought to the attention of the child’s physician. These arousals may be noted as an incidental finding in children who are studied by overnight polysomnography for other reasons. At the other end of the spectrum are sleep terrors, which are the most dramatic and least common of the disorders of arousal. They are seen more often in older children and young adults. The events usually begin precipitously with the child bolting upright with a scream. There is generally a high level of autonomic arousal. The eyes are usually open, the heart is racing, and often there is diaphoresis and mydriasis. The facial expression is one of intense fear. A youngster may jump out of bed and run blindly as if to frantically avoid some unseen threat.



Sleepwalking


The presentation of sleepwalking is similar at all ages. At a minimum, there is a partial arousal from sleep with some ambulation. The young child may simply awaken and crawl about in the crib before returning to sleep; such events may go unnoticed unless the child sleeps with another family member. An older child may get up and walk to the parents’ room, or he may simply be found asleep at a location different from where he went to bed, with no recollection of having left his bed. Some inappropriate behavior, such as urinating in the closet or next to the toilet, is common. A sleepwalking child may be easily led back to bed, with little evidence of a complete awakening and no recall of the event the next day. Sleepwalking can be triggered in most children by simply standing them up within the first few hours of sleep onset. Because the child is unaware of their environment during a sleepwalking episode, they may be injured or put themselves into dangerous situations during a quiet sleepwalking episode.


Sleepwalking is common in children, as documented in two large, population-based studies by Klackenberg4 in Sweden, and Laberge and Petit5,6 in Quebec. Klackenberg studied a group of 212 randomly selected children in Stockholm, longitudinally from ages 6 to 16 years. The prevalence of quiet sleepwalking (occurring at least once during the 10-year data collection period in this group) was 40%. The yearly incidence varied from 6% to 17%, although only 3% had more than one episode per month. In Klackenberg’s study, the sleepwalking persisted for 5 years in 33% of children and for over 10 years in 12%.


Laberge5 and Petit et al.6 studied 2675 randomly selected children in Quebec who were part of the Québec Longitudinal Study of Child Development conducted by the Québec Institute of Statistics . The parents completed a yearly sleep questionnaire regarding the presence of parasomnias in their children from 2.5 to 13 years of age. Occasional or frequent sleepwalking was present in 14% of the children at some time during that period. The yearly incidence of sleepwalking, as shown in Table 39.1, varied from 2.5% to 7.5%. Table 39.2 describes the ages of onset and offset of sleepwalking and confusional arousals/night terrors . In the majority of these children, the sleepwalking began and ended between the ages of 3 and 13 years. At 13 years of age 3% of the children were still sleepwalking. There was no gender difference in sleepwalking prevalence. In the studies of Laberge, Petit and Klackenburg, sleepwalking was frequently seen in those children who had confusional arousals at a younger age.





Confusional Arousals/Sleep Terrors


The Confusional arousal/sleep terrors seem bizarre and are frightening for parents. The arousal usually starts with some movements and moaning, progressing to crying, often in association with intense thrashing about in the bed or crib. An infant may be described simply as crying inconsolably. These arousals are common in infants and toddlers. The child is typically described as appearing confused, with the eyes open or closed. These events can last anywhere from a few minutes to over 1 hour, with 5 to 15 minutes being typical. Even if the child calls for the parents, the child often does not recognize them. Even vigorous attempts to wake the child are often unsuccessful. Holding and cuddling usually do not provide reassurance; instead, the child often resists, twists, and pushes away and may become more agitated. It is the parents’ inability to comfort their child, who appears to be in great distress, that is often of the greatest concern to them.


In the studies of Laberge5 and Petit,6 there was no distinction between confusional arousals, sleep terrors, and night terrors. However, from the age distribution and the description of the events, the current nomenclature would characterize these as confusional arousals. In the Laberge and Petit studies, the prevalence of confusional arousals between the ages of 2.5 and 6 years was 39.8% (see Table 39.1). The yearly incidence was 19.9% at age 2.5 years, 11.3% at age 6 years, 3.8% at 11 years of age, and 1.2% at 13 years of age . In 85% of the children the confusional arousals first appeared between the ages of 3 and 10 years, and in the majority of these children, they disappeared before the age of 10 years (see Table 39.2). The confusional arousals persisted beyond 13 years of age in 6.7% of the children.


In the studies of Laberge, Petit, and Klackenberg, sleepwalking and confusional arousals were often seen in the same child at different ages Thirty-six percent of the children with sleepwalking in the study of Laberge had confusional arousals as preschoolers, and all of the children with confusional arousals in Klackenburg’s study had at least one episode of sleepwalking when they were older.



Pathophysiology of Disorders of Arousal


Disorders of arousal are best understood as a dissociated state during which elements of wakefulness, and NREM sleep occur simultaneously resulting in behavior that is neither fully awake or fully asleep. This concept, first put forward by Mahowald7,8 is consistent with the current understanding of sleep neurophysiology. During the disorders of arousal, some facets of wakefulness appear during the transition out of slow-wave sleep. This usually occurs at the end of the first sleep cycle. As a consequence, the transition out of slow-wave sleep, which is usually behaviorally inapparent, can be dramatic. The child appears caught between deep NREM sleep and wakefulness. The child’s behavior at this time has elements that we associate with wakefulness (walking, talking, crying, running) complex motor behaviors) and sleeping (misperception of and unresponsiveness to the environment, high arousal threshold, amnesia, automatic behavior) occurring simultaneously. The EEG during these arousals from sleep is typically characterized by a mixture of waking and sleeping rhythms with the simultaneous occurrence of alpha, theta, and delta frequencies, and suggests that different areas of the brain are in different states simultaneously. This dissociated state is inherently unstable, and eventually one state is fully declared. In most cases, the child appears to simply return to quiet sleep. Alternatively, the child may awaken totally but will have no recall of the arousal and will usually rapidly return to sleep.


The causes of the disorders of arousal are multifactorial. Genetic predisposition, homeostatic drive, sleep–wake cycling and synchronization, and behavioral and emotional states all seem to play some role in the clinical appearance of the disorders of arousal. Of these factors, genetic predisposition is probably the most important, though the mechanism is unknown. Sleep–wake cycling and synchronization are affected by age, homeostatic factors, circadian factors, hormones, and drugs. Affective disorders, anxiety, and environmental stress have all been identified as important factors in the appearance of the disorders of arousal in clinical studies,9,10 although the mechanisms by which these factors lead to the arousal is not known.



Genetics of Disorders of Arousal


A familial predisposition toward the disorders of arousal has been recognized since these disorders were first described. The genetics of the disorders of arousal has been explored by Hublin et al.11,12 and Nguyen et al.13 (in population-based twin studies) and also by Lecendreux.14 In Hublin’s retrospective study of adults the phenotypic variance of sleepwalking was attributable to genetic factors at 65%, which he believed was the result of many genes, each with minor effects. In Nguyen’s study, environmental information was gathered in an attempt to understand the relative contribution of genetic, shared environmental, and non-shared environmental factors leading to confusional arousals in children. They concluded that the best explanation was a two-component model with 44% of the variance explained by genetic factors and 56% of the variance explained by non-shared environmental factors. These results are consistent with the results of Lecendreux, who looked at human leukocyte antigens and sleepwalking. The familial predisposition to disorders of arousal may be secondary to the familial aggregation of restless leg syndrome or sleep-disordered breathing, which are recognized as triggers for disorders of arousal.18 A positive family history of a first-degree relative with a disorder of arousal is present in 60% of the children with a disorder of arousal compared with 30% in children without disorders of arousal.



Sleep Homeostasis and Disorders of Arousal


There is good theoretical support and some experimental evidence that the familial predisposition toward the disorders of arousal is mediated by the genetic control of the of the sleep homeostatic process. This process has been shown to be under strong genetic control in animal studies.16 Studies in mice have demonstrated that sleep loss leads to an increase in homeostatic drive, with a change in slow-wave sleep activity as measured by delta power, in a dose–response fashion that varies with the duration of prior wakefulness and is different in different genotypes. A quantitative trait–loci analysis revealed that this trait is the product of multiple genes. Human EEG studies have also shown that slow-wave sleep and EEG slow-wave activity are markers for measuring homeostatic drive.17–19 Increases in slow-wave sleep and slow-wave activity occur after sleep deprivation and decline after sleep. The synchronization of the homeostatic and circadian processes optimizes the quality of sleep and wakefulness. This interaction is described in a comprehensive article by Dijk and Lockley.18 Adequate sleep duration occurs only when the circadian and homeostatic systems are fully synchronized. The clinical implication of this observation is that a child with an irregular and/or chaotic sleep–wake schedule will simply not be able to have optimum synchronization of the homeostatic and circadian systems; this inevitably leads to sleep disruption and sleep deprivation, which may lead to a clinical event in a child who may be predisposed to the disorders of arousal.

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Jul 11, 2016 | Posted by in PEDIATRICS | Comments Off on Disorders of Arousal

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