The parasomnias are a group of sleep disorders that consist of undesirable behavioral phenomena that occur predominantly during sleep. The parasomnias represent disorders of arousal, partial arousal, and sleep stage transition.1 Although these disorders are quite variable in their manifestations, activation of the autonomic nervous system and skeletal muscles are common features. Parents and other caregivers often view parasomnias as frightening nighttime episodes that are disruptive to family life. In some situations, these events lead to concern over other medical problems such as nocturnal seizures, respiratory difficulties, or emotional problems. Some parasomnias are associated with potentially injurious behavior, such as sleepwalking into dangerous situations. Each of the parasomnias can occur in otherwise healthy children, and thus, many children are thought to manifest altered physiologic processes during sleep, rather than experience true pathologic changes. Nonetheless, when these nighttime events occur frequently or with extreme severity, children may experience discomfort, embarrassment, or anxiety, and sleep may be disrupted for other family members. The parasomnias rarely cause complaints of insomnia or excessive daytime sleepiness.
The purpose of this article is to provide an introduction to the parasomnias, including a brief review of the physiologic basis, proper identification and classification, and a practical approach to diagnosis and treatment. As with all episodic disturbances, the cornerstone of diagnosis is a detailed history.
OVERVIEW OF SLEEP PHYSIOLOGY AND PARASOMNIA CLASSIFICATION
The parasomnias are divided into four broad groups: the arousal disorders, the sleep-wake transition disorders, parasomnias usually associated with rapid eye movement (REM) sleep, and the other parasomnias.1 Table 1 summarizes the parasomnias seen commonly in pediatric patients. This classification is based on the International Classification of Sleep Disorders (1990), which is the accepted standard for diagnostic and epidemiologic purposes in sleep disorders medicine.
Sleep is a dynamic physiologic process characterized by varying degrees of unresponsiveness to the environment. During the first few years of life, a number of important developmental changes occur, leading to the normal adult sleep/wake pattern. Two distinct sleep states have been identified based on specific physiologic variables - rapid eye movement (REM) and non-rapid eye movement (non-REM) sleep. With maturation of the child's central nervous system, predictable changes occur with regard to the timing and character of these states. Thus, certain age-related differences exist with regard to the presentation and natural history of the parasomnias, and a full understanding of the parasomnias requires an introduction to sleep physiology. The following overview is provided as background, leading to a rational approach for classification of the parasomnias based on known patterns of sleep physiology. Several excellent sources are available to provide greater detail regarding sleep physiology.2-4
Non-REM sleep occupies the majority of nighttime sleep in older children and adults. This state is subdivided into four discrete stages based on the electroencephalogram (EEG). The four stages of nonREM sleep range from stage 1 (roughly equivalent to drowsiness) to stage 4 (deep non-REM sleep with a high arousal threshold). Stage 1 is characterized by mild slowing of the EEG, low threshold for arousal, and mild amnesia for events just before sleep onset. Stage 2 sleep is identified by the appearance of sleep spindles and K complexes on the EEG. Stages 3 and 4 (collectively known as slow-wave sleep) are characterized by high-voltage slow waves in all regions on the EEG, as well as deepening of respirations and gradual slowing of heart rate. The arousal threshold for stage 4 sleep is quite high in children, as manifested by failure of the child to arouse during loud noises and despite being moved to a new location.
REM sleep is a physiologically distinct stage characterized by EEG activation resembling a wakefulness pattern, bursts of REMs, and relative atonia in the major muscle groups. There is a predictable cycle of non-REM and REM sleep throughout the night. REM and non-REM sleep alternate with a period of 90 to 100 minutes, with progressive increases in the duration of REM episodes across the night. The majority of dreaming occurs during REM sleep, and non-REM sleep is associated with a paucity of mentation. The sleep of older children and adults includes approximately 75% non-REM and 25% REM sleep. In normal individuals, sleep proceeds through an orderly sequence characterized by descent from drowsiness into deeper stages of non-REM sleep, interrupted periodically by episodes of REM sleep of increasing duration followed by spontaneous arousal in the morning. Modulation of sleep/wake states across the 24-hour day is accomplished through the complex interaction of several neuronal populations, including cortical, subcortical, and brain stem pathways, which function in concert to support normal sleep/wake cycling.
The parasomnias are not thought to indicate pathologic disruption of these processes, but to represent undesirable behaviors that result from central nervous system activation during sleep. As previously stated, for most individuals, sleep consists of an orderly progression from one stage to the next in a predictable fashion. In some individuals, the various physiologic and behavioral markers of sleep become dissociated leading to problems with transitions between states, or abnormal "hybrid" states in which the subject exhibits features of more than one state simultaneously. For example, the child with sleepwalking exhibits behavioral evidence of arousal and low levels of interaction with the environment while EEG background continues to reflect deep non-REM sleep.
THE AROUSAL DISORDERS
The disorders of arousal are grouped together because they are thought to occur due to impaired arousal (partial arousal) from deep non-REM sleep. Sleepwalking, sleep terrors, and confusional arousals are common in children and are the prototypic parasomnias.5,6
Confusional arousals, which were previously referred to as sleep drunkenness or excessive sleep inertia, consist of disorientation in time and space, slow speech and mentation, and memory impairment.5,6 Individuals may exhibit bizarre behavior such as placing a piece of clothing in the refrigerator. The confusional episode may last minutes to hours, and most individuals have no recollection of events during the period of confusion. At times, the episodes can be precipitated by sudden or forced arousal during the first third of the night, when deep non-REM sleep predominates. Recovery from sleep deprivation and taking certain central nervous system depressants may increase the likelihood of confusional arousals. Confusional arousals are almost universal among young children, and the natural history usually involves a gradual decrease in frequency with age. In rare cases, the individual experiences aggressive or injurious behavior. Some patients exhibit complex motor automatisms, which may require differentiation from nocturnal seizures. Diagnosis can usually be reached with patient history, but certain patients may require an EEG or video/EEG monitoring to evaluate for possible seizures.
Sleepwalking consists of a series of complex behaviors that are initiated during non-REM sleep and result in walking during sleep.6,7 Episodes can range from quiet walking about the room to frantic, agitated attempts to run or "escape." Often, the child walks toward the parents' bedroom or toward a light or noise. The child's eyes are typically open but the expression is dull or glassy, with slow or absent response to questions. When the child is returned to bed, he or she typically returns to sleep uneventfully and later has no recollection of the episode. In some cases, the parent is unaware of the sleepwalking until the child is found in a new location the following morning. In rare cases, subjects may walk into dangerous situations, such as walking out into a busy street or into the snow, falling down stairs, running into or through windows, or emerging from the home into an unsafe neighborhood. In cases involving the potential for injury, parents should consider the use of barriers to keep the child in his or her bedroom. Examples include "infant gates" applied to the bedroom door or latches to outside doors.
The typical age of onset for sleepwalking is 4 to 8 years, although the problem can occur any time after the child learns to walk.7 In a longitudinal study by Klackenberg8 involving 212 randomly selected children from Stockholm, the incidence of quiet sleepwalking was 40%. The yearly prevalence ranged from 6% to 17%, but only 2% to 3% of the children experienced more than one episode per month. Sleepwalking persisted for over 10 years in 12%. Genetic and developmental factors are thought to play a role in sleepwalking, and several studies have demonstrated a familial tendency.7,9 Sleepwalking may coexist with other disorders of arousal, such as confusional arousals, and the agitated form of sleepwalking may show overlap with sleep terrors. The likelihood of sleepwalking may increase during febrile illness and following sleep deprivation. Several medications can exacerbate sleepwalking, including chloral hydrate, lithium, and certain phenothiazines. Episodes may be precipitated by internal or external stimuli such as a distended bladder or loud noises. Diagnosis is based on the history, and, in rare cases, a routine EEG or video/EEG monitoring may be necessary to exclude seizures when complex automatisms or unusual behaviors are present. Intense fear or panic during the episodes should lead to consideration of other parasomnias such as the REM sleep behavior disorder or panic attacks. Psychosocial complications may occur in children with frequent sleepwalking, including avoidance of visiting overnight with friends or summer camp because of embarrassment or ridicule.
Classification of Parasomnias*
Sleep terrors are characterized by a sudden arousal from non-REM sleep with a piercing scream or cry accompanied by autonomic and behavioral manifestations of intense fear.5,6,9"11 The events begin abruptly with the child sitting up in bed followed by what parents often describe as a dramatic "blood-curdling" scream. There is prominent autonomic activity including racing heartbeat, wide open eyes, rapid breathing, diaphoresis, and flushing. The child is usually unresponsive to stimuli and shows little awareness despite vigorous attempts by the parent to reorient or calm the child. Amnesia occurs with the episodes, although there may be brief fragments of memory or dream-like mentation.
Sleep terrors occur most commonly in children between 4 and 12 years of age. They usually resolve during adolescence, but they can occur in adults. Although the incidence of psychopathology among children with sleep terrors is no different than that in the general population, adults with this disorder may have an increased association with psychiatric problems. Sleep terrors are somewhat more common in boys than girls, and the disorder may occur in more than one family member. Episodes can be precipitated by fever, sleep deprivation, or medications that affect the central nervous system. Complications of sleep terrors can include social embarrassment and potential injury due to running or attempting to fight with others. Sleep terrors should be differentiated from nightmares, which are characterized by vivid dream recall and fairly rapid return of consciousness when awakened. Nightmares usually occur in the last third of the night, when REM sleep predominates, whereas sleep terrors occur in the first third of the night during deep non-REM sleep. Nightmares have less autonomic activation than sleep terrors and there are fewer vocalizations noted. At times, children may exhibit "overlap" episodes with features of sleep terrors, confusional arousal, and sleepwalking. In some cases, sleep terrors should be differentiated from nocturnal seizures with prominent autonomic activity.
SLEEP-WAKE TRANSITION DISORDERS
The sleep-wake transition disorders are very common during childhood and occur during the transition from wakefulness to sleep, from sleep to wakefulness, or, less commonly, during sleep stage transitions. Each of these disorders can occur in otherwise healthy individuals, and the problem is often regarded as altered physiology rather than pathophysiology.12 When the problem occurs with great frequency or severity, the disorder can lead to significant discomfort or pain in the child and anxiety for the caregiver. Rhythmic movement disorders may also occur during wakefulness, particularly in children with mental retardation, autism, or other neurologic problems.
Rhythmic movement disorder is defined as a group of stereotyped, repetitive movements involving large muscles, usually of the head and neck, which typically occur immediately before sleep onset and are sustained into light sleep.13,14 Repetitive head banging, body rocking, and head rolling are the most common forms of this disorder. In the past, a variety of other terms were used, including jactaub capitis nocturna and head banging, but the preferred term is rhythmic movement disorder because the events often involve parts of the body other than the head and the episodes are associated with sleep during the day or night.
In a study involving 525 healthy children, Sallustio and Atwell15 documented body rocking in 19%, head rolling in 6.3%, and head banging in 5.1%. Among those with head banging, there were almost three times as many boys as girls, whereas no sex differences were noted in the other two behaviors. Klackenberg reported a combined incidence of all rhythmic movement disorders of 60% at 9 months, 22% at 2 years, and 5% at 5 years.14 The age at onset is typically in the first 9 months of life, and onset after 2 years is unusual. Most episodes occur during sleep onset and last up to 15 minutes, although some children have prolonged episodes lasting up to several hours. Most children experience spontaneous improvement or complete resolution by 4 years of age, although the movements can persist for years in certain individuals. The movements are persistent in several groups of children, including those with mental retardation, autism, posttraumatic encephalopathy, and severe psychiatric disturbances. The precise etiology for the episodes is unknown, but vestibular stimulation has been proposed as one explanation.13 Traumatic injury due to head banging is rare but subdural hematomas, corneal abrasions, cataracts, and retinal petechiae can occur in more dramatic cases. Chronic skin irritation can predispose to skin breakdown or callus formation. The sounds associated with rhythmic head banging are often distressing to family members, and in severe cases, protective measures such as padding the head of the bed and bedrails or use of a helmet may be necessary. Head banging may be the sole manifestation of seizure activity in rare cases.16
Sleep starts (also known as hyponic jerks) are sudden, brief contractions of the legs, sometimes involving the arms and head, which occur at sleep onset. On some occasions, the movements are associated with a feeling of tailing or a sudden visual image. The jerks may be spontaneous or induced by external stimuli such as noise or light.17,18 Sleep starts may occur at any age but they are most common in adults. The experience of sleep starts is almost universal among adults and they usually require no specific evaluation or treatment. The frequency of sleep starts may be increased by excessive caffeine or other stimulants, intense physical activity just before the time of sleep, and emotional stress.
Sleep talking is an almost universal experience that consists of the utterance of speech or sounds during sleep wirhout simultaneous subjective awareness of the event. The speech is usually brief and fragmentary, but more severe cases can involve long, rambling speeches with strong emotional content such as anger or hostility. The speech can be spontaneous or induced by conversation from another person. As with the other parasomnias, fever and emotional stress may exacerbate sleep talking. The episodes have been documented to occur during any stage of sleep, and sleep talking may coexist with sleepwalking.19 The disorder is benign and usually self-limited.
Nocturnal leg cramps are painful sensations of muscular tightness or tension, usually in the calf but occasionally in the foot, that occur during the sleep episode.20,21 The cramp can usually be relieved by local massage, heat, or movement of the affected limb. Nocturnal leg cramps can occur at any time beyond infancy, but incidence is greatest during adulthood. The problem may appear for the first time during pregnancy or in association with diabetes mellitus, metabolic disorders, neuromuscular disorders, or arthritis. In some cases, leg cramps may lead to insomnia or daytime fatigue due to sleep disruption.
PARASOMNIAS USUALLY ASSOCIATED WITH REM SLEEP
Nightmares are frightening dreams that usually awaken the child from REM sleep.5,22.23 Often the nightmare is long and complicated, leading to increasing fright followed by arousal. There is mild to moderate autonomic activity such as tachypnea, tachycardia, and diaphoresis. The child usually recalls the dream in vivid detail. In comparison with sleep terrors, there is less motoric activity and autonomic activation. Nightmares usually appear during the preschool or early elementary years, with a waxing and waning in frequency. A distinct subgroup will have nightmares that persist into adolescence or even adulthood. Among those with persistent nightmares, psychiatric problems or a history of adjustment problems during childhood may be present. Certain medications may trigger nightmares, including L-dopa, beta-adrenergic blockers, and withdrawal of REM-suppressant drugs. Parents of children with occasional nightmares should be reassured about the benign nature of these episodes, but children with frequent or highly disturbing nightmares may require psychological evaluation and intervention.
Key Elements in the History Regarding Parasomnias
Sleep paralysis consists of a period of inability to perform voluntary movements either at sleep onset or on awakening from sleep.24,25 This disorder is an example of state dissociation, in which features of wakefulness and REM-related atonia are present simultaneously. The experience is often frightening for the individual, and there may be a sensation of inability to breathe. The episodes usually last for a few seconds to a few minutes and may terminate following stimulation such as being touched by another person or noise. Sleep paralysis usually begins during adolescence but it may occur during childhood or adulthood. Isolated sleep paralysis occurs at some point in at least 50% of the general population. It may also occur in association with other sleep disorders such as narcolepsy.
The REM sleep behavior disorder is a recently recognized problem characterized by the appearance of elaborate motor activity associated with dream mentation along with intermittent loss of REM sleep muscle atonia.26 Examples of motor activity include punching, kicking, leaping, and running from the bed, often associated with risk of injury to the patient or bed partner. These violent episodes typically occur approximately 90 minutes after sleep onset, during the first REM sleep episode. Although this interesting sleep disorder has been observed mainly in older adults, it is likely that the problem will be identified in young adults and even children with greater frequency. Although most cases are idiopathic, several neurologic conditions are associated with REM sleep behavior disorder, including stroke, multiple sclerosis, Parkinson's disease, and dementia. Pathologic findings at autopsy in some cases have indicated bilateral thalamic or brain stem lesions, or diffuse hemispheric lesions.27
The other parasomnias are listed in Table 1. They are a diverse group of disorders with no single pathologic basis. It is likely that this group will grow and that certain of the disorders can be grouped together based on underlying physiology.
The approach to management of parasomnias in children begins with a thorough history directed toward establishment of a proper diagnosis. Table 2 reviews the key elements of the history that may help differentiate the parasomnias from other episodic disturbances. Many parents have difficulty providing a detailed history, and significant time may be required to reconstruct the exact order of events. The physical examination is useful in searching for underlying medical conditions, but the examination rarely adds new information that changes the clinical impression formed from the history. In some situations, parents can be instructed to keep a detailed log of sleep/wake cycling and to record observations of episodes in writing for review with the physician. Personal video cameras are commonplace, and parents can provide significant information for the physician by videotaping representative episodes in the home environment. The history and physical examination are usually adequate to identify most parasomnias. In some situations, particularly when nocturnal seizures are a possibility, routine EEG or a sleep-deprived EEG may be helpful in searching for epileptiform abnormalities. Video/EEG monitoring may be required in some cases and the study should be scheduled to occur during times when the child is most likely to experience clinical events. Newer techniques with ambulatory EEG may offer the advantage of recording activity in the home environment at less cost than inpatient video/EEG monitoring. Possible artifact and the absence of videotape confirmation of the episode are drawbacks, however. When the differential diagnosis includes respiratory disturbance during sleep, overnight polysomnography is indicated, and the study can be adapted to include additional EEG channels if necessary. Neuroimaging is typically not necessary unless there is concern over the possibility of a structural lesion such as an intracranial mass, congenital brain malformation, or hydrocephalus.
Parasomnias are often disturbing to parents and family members, and proper diagnosis and education of the family are important aspects of management. Parents should be counseled regarding removing dangerous objects and providing barriers to the child's escape when there is potential for injury. Reassurance that the episodes are not harmful is important, and some families may require additional emotional support or counseling. Efforts should be directed toward maximizing the child's quality of life through proper education and encouraging a full and normal lifestyle. Although some parents may pressure the physician to "fix" the problem with medications, pharmacologic intervention is usually not indicated and is rarely helpful over the long term. Many medications may actually contribute to greater sleep disruption. Counseling regarding proper sleep hygiene and the natural history of the parasomnias is important.
In summary, management of the parasomnias is based on a thorough history and appropriate diagnosis. The parasomnias occur most often in otherwise healthy children and adolescents, but frequent or severe episodes may signal underlying medical or psychological dysfunction. Ancillary diagnostic tests are occasionally required for more difficult cases, including EEG, video/EEG monitoring, overnight polysomnography, and neuroimaging.
1. Diagnostic Classification Steering Committee, Thorpy MJ, chairman. International Classification of Sleep Disorders: Diagnostic and Coding Manual. Rochester, Minn: American Sleep Disorders Association; 1990:141.
2. Carskadon MA, Dement W. Normal human sleep: an overview. In: Kryger MH, Roth T, Dement WC, eds. Principles end Practice of Sleep Medicine. 2nd ed. Philadelphia, Pa: WB Saunders Coi 1994:16-25.
3. Anders TF, Sadeh A, Appareddy V. Normal sleep in neonates and children. In: Fetber R, Kryger M, eds. Principle] and Practice of Sleep Medicine in the Child. Philadelphia, Pa: WB Saunders Co; 1995:7-18.
4. Rofrwarg H, Muzio J, Dement W. Ontogenetic development of the human sleepdream cycle. Science. 1966:152:604.
5. MahowaM MW, Rosen GM. Parasomnias in children. Pediatrician. 1990;17:21-31.
6. Rosen G, Mahowald M, Ferber R. Sleepwalking, confusional arousals, and sleep terrors in the child. In: Ferber R, Kryger M, eds. Principles and Practice of Sleep Medicine in the Child. Philadelphia, Pa: WB Saunders Co; 1995:99-106.
7. Diagnostic Classification Steering Committee, Thorpy MJ, chairman internarionai Classification of Sleep Disorders: Diagnostic and Coding Manual. Rochester. Minn: American Sleep Disorders Association; 1990:145-147.
8. Klackenberg G. Somnambulism in children: prevalence, course and behavioral correlations. Acta Pediatr Scand. 1982;71:495-499.
9. Kales A, Soldatos CR, Bixler BO, et al. Hereditary factors in sleep walking and night terrors. Br J Psychiatry. 1980;137:111-118.
10. Fisher C, Kahn E, Edwards D, Davis D. A psychophysiological study of nightmares and night tenors: physiological aspects of the stage 4 night terror. J Nerv Mem Dis. 1973;157:75-98.
11. Diagnostic Classification Steering Committee, Thorpy MJ, chairman, Intemarionai Classification of Sleep Disorders: Diagnostic and Coding Manual. Rochester, Minn: American Sleep Disorders Association; 1990:147-150.
12. Diagnostic Classification Steering Committee, Thotpy MJ, chairman. International Classification of Sleep Disorders: Diagnostic and Coding Manual. Rocheste', Minn: American Sleep Disorders Association; 1990:151.
13. Diagnostic Classification Steering Committee, Thorpy MJ, chairman. Iruemauonoi Classification of Sleep Disorders: Diagnostic and Coding Manual. Rochester, Minn: American Sleep Disorders Association-, 1990:151-154.
14. Klackenburg G. Rhythmic movements in infancy and earty childhood. Acta Pediao Stand Supft. 1971;224:74-83.
15. Sallustio F, Atwell C Body rocking, head banging and head rolling in normal children. J Pediatr. 1978:93:704-708.
16. Guillerninaule C, Syrvestri R. Disorden of arousal and epilepsy during sleep. In: Scerman MB, Shouse MN. Passouant P, eds. Sleep and Epilepsy. New York, NY: Academic Press; 1982:513-531.
17. Diagnostic Classification Steering Committee, Thotpy MJ, chairman. International Classification of Sleep Disorders: Diagnostic and Coding Manual. Rochester, Minn: American Sleep Disorders Association; 1990:155-157.
18. Oswald I. Sudden bodily jerks on falling asleep. Brom 1959;2:92-93.
19. Diagnostic Classification Steering Committee, Thorpy MJ, chairmar. International Classification of Sleep Disorders: Diagnostic and Coding Manual. Rochester. Minn: American Sleep Disorders Association; 1990:157-159.
20. Weiner IH, Weiner HL. Nocturnal leg muscle cramps. JAMA. 1980;244:2332-2333.
21. Diagnostic Classification Steering Committee. Thotpy MJ, chairman. International Classification of Sleep Disorders: Diagnostic and Coding Manual. Rochester, Minn: American Sleep Disorders Association; 1990:159-161.
22. Fisher CJ, Byrne J1 Edwards T, Kahn E. A psychophysiological study of nightmares. J Am Psychoanal Assoc. 1970;18:747-782.
23. Diagnostic Classification Steering Committee, Thorpy MJ, chairman. International Classification of Sleep Disorders: Diagnostic and Coding Manual. Rochester, Minn; American Sleep Disorders Association; 1990:162-165.
24. Goode GB. Sleep paralysis. Arch Neurol. 1962;6:228-234.
25. Diagnostic Classification Steering Committee, Thorpy MJ, chairman. International Classification of Sleep Disorders: Diagnostic and Coding Manual. Rochester, Minn: American Sleep Disorders Association; 1990:166-169.
26. Schenck CH. Bundlie SR, Patterson AL, Muhowald MW. Rapid eye movement sleep behavior disorder: a treatable parasomnia affecting older males. JAMA. 1987;257:1786-1789.
27. Diagnostic Classification Steering Committee. Thorpy MJ, chairman. International Classification of Sleep Disorders: Diagnostic and Coding Manual. Rochester, Minn: American Sleep Disorders Association; 1990:177-180.
Classification of Parasomnias*
Key Elements in the History Regarding Parasomnias