This is a 4 year old boy who is brought to the office by his single mother with a chief complaint of screaming at night for about a year. He has been in good health otherwise with no recent history of otitis or respiratory infection. There is no history of nervous system malformation, seizure, or sleep walking. According to his mother, she would hear a chilling scream, rush to her son, and find him sitting up in bed, sweating with a glassy stare. There is no response when she talks to him, and when she tries to hug him, he usually resists. But when her son does answer after more vigorous shaking, he seems confused and disoriented. This mostly happens approximately at midnight, 2-3 hours after his bedtime. In the morning he would seem fine and not remember having any nightmares or screaming.
Exam: VS T 37.5, P 90, R 24, BP 92/53. He is a shy, healthy looking boy in no apparent distress. His examination is normal.
He is referred to a sleep specialist who assesses the boy as having sleep terrors. His mother is taught to help avoid stresses and fatigue for her son during the daytime. Short naps of 30-60 minutes in late afternoon are suggested. His mother is told that diazepam may be prescribed if his problem worsen, but most of the time, children will outgrow this disorder.
When children present with sleep problems, a careful history should be taken (1). This includes age of onset, patterns of daytime sleepiness and napping, questions about snoring and apnea, sleep related behaviors such as talking and head banging, psychiatric assessment regarding separation anxiety and nightmares, relevant medical/neurological conditions such as headaches, and mental retardation, and family histories of sleep disorders.
Studies such as polysomnography (PSG), limb actigraphy, and multiple sleep latency test (MSLT) can be useful in diagnosing the cause of the sleep problem. PSG includes measurements of eye muscle movement, EMG, EEG, EKG, respiratory measurements (i.e., thoracic/abdominal excursion, air flow, and oximetry) during sleep. MSLT is based on PSG that objectively measures daytime sleepiness by recording sleep onset and type of sleep with 5 regularly spaced daytime naps. Limb actigraphy uses an instrument resembling a wrist watch that detects body movements continuously for 3 days. However, for disorders that are more sporadic, PSG may not be definitive. In cases of arousal disorders (sleep terror and sleep walking), having the parents record the episodes on a video camcorder may be more useful. Sleep disorders can be categorized into dyssomnias, parasomnias, and sleep disorders due to medical or psychiatric conditions (2).
Normal sleep is composed of rapid-eye-movement (REM) and non-REM (NREM) types. REM sleep is the dreaming stage of sleep, whereas NREM is sleep that is further divided into 4 stages depending on the PSG readings. Stage 1 NREM sleep can be defined as "drowsiness" where alpha waves of wakefulness are replaced by theta waves in EEG, and during which slow, rolling eye movements are observed with slightly decreased tonicity in EMG recordings. This is followed by K complexes characteristic of Stage 2 NREM sleep. Stages 3 and 4 of NREM sleep are known as slow-wave sleep where delta waves on EEG dominate. In stage 3, delta waves are present in 20-50% of the EEG, while in stage 4, delta waves are present in >50% of the EEG (3,4).
Dyssomnias are disturbances of normal sleep or sleep rhythm pattern. This disorder is characterized by not enough, too much, or inefficient sleep. Dyssomnias can be broken down into 3 categories: intrinsic dyssomnias, extrinsic dyssomnias, and circadian dyssomnias (5).
Intrinsic dyssomnias are due to causes within the body and include breathing related sleep disorders (sleep apnea) and narcolepsy. Sleep apnea occurs when air flow is completely stopped and is diagnosed when there are 5 apneas or 10 apnea-hypopnea episodes per hour of sleep. Compared to apnea, hypopnea is shorter duration of decreased ventilation. However, the precise criteria for defining hypopnea is controversial. In general, hypopnea can be thought of as episode where airflow is reduced by one-half to two-thirds (6). Audio tape recording of the episode can also aid in the diagnosis. Apnea by itself is not a problem except when it exceeds 10 seconds in duration. Patients are not aware of their apneas but sometimes do wake up with a choking feeling.
There are 3 types of sleep apnea: central, obstructive, and mixed sleep apnea. Central apnea results from no respiratory effort because of brainstem respiratory neuronal immaturity, which is commonly seen transiently in premature babies and newborns. Obstructive sleep apnea is caused by airway obstruction. In young children, the obstruction is most often due to enlarged tonsils and adenoids and not usually from severe obesity (2). Surgical removal of the enlarged tonsils and adenoids may be curative. Apnea is accompanied by increased thoracic and diaphragmatic respiratory effort without air exchange due to upper airway obstruction. Mixed sleep apnea combines features of both central and obstructive causes.
Because of apneic episodes, the patient experiences many short arousals to restore adequate oxygenation. These arousals can severely interrupt the sleep cycle. Thus, symptoms of daytime sleepiness and inattention are evident. In toddlers, growth retardation similar to that seen in failure to thrive can be observed possibly associated with disruption of growth hormone secretion during fragmented sleep.
A related disorder in children is central hypoventilation syndrome (or Ondine's curse) caused by central chemoreceptor impairment leading to nocturnal seizures and hypoxia (7). Treatment includes mechanical ventilation or phrenic nerve pacing (3). Other hypoventilation syndromes include Pickwickian syndrome (named for the Joe, the fat boy in Dickens' Pickwick Papers), a rare complication of extreme obesity characterized by hypersomnolence with apneic pauses, polycythemia, and eventual right-sided heart failure (8,9). Likewise Prader-Willi syndrome can also cause obstructive sleep apnea (10). Prader-Willi syndrome is a genetic disorder due to deletion of q12 in the long arm of the paternal chromosome 15. Initially, the infant presents with hypotonia followed by rapid weight gain after 1 year of age leading to morbid obesity (11,12, 13). In cases of Pickwickian and Prader-Willi syndromes, reducing weight is of primary importance and should be achieved as fast as is feasible (14). Examples of other conditions predisposing to obstructive sleep disorders are Down syndrome, craniofacial anomalies, mucopolysaccharidoses, and neuromuscular disorders.
Narcolepsy is the only REM sleep dyssomnia. Its peak incidence (<1%) is between 15 to 25 years of age (5). Its etiology is unknown, but there is strong genetic predisposition (with HLA-DR2 and HLA-Dqw1, and first degree relatives of affected individuals being eight times more likely to suffer from REM sleep disorders) (2). In severe cases, narcolepsy consists of a clinical tetrad: 1) sleep attack characterized by an irresistible urge to sleep for 5-20 minutes, 2) cataplexy (or an intrusion of REM atonia while awake), manifested as an abrupt muscle tone loss (total loss of whole body muscle tone) triggered by strong emotions such as anger (the patient may be fully awake, but is unable to move), 3) sleep paralysis, which is REM atonia at sleep-wake transition (when falling asleep or waking up) when the patient briefly cannot move, and 4) hypnagogic hallucinations in which dreams continue into the waking state resulting in illusions or hallucinations.
PSG is required for the diagnosis of narcolepsy. Treatment is symptomatic. Regular sleeping and rising times are recommended with scheduled naps 2-3 times a day. Psychosocial counseling and support are important as narcolepsy is a debilitating life-long condition once diagnosed. Stimulants maybe indicated by excessive daytime sleepiness. For treating cataplexy, tricyclic antidepressants and clomipramine have been successful.
Unlike intrinsic dyssomnias, extrinsic dyssomnias are due to external causes and includes protodyssomnias (an inability to fall asleep and stay asleep) of infancy and insomnias of childhood (2). Examples include night waking, and difficulty falling asleep. Predisposing factors include previous behavior reinforcement patterns, child temperament (e.g., ADHD), poor nutrition, milk allergy, marital dispute, and physical discomfort. Currently, it is not known whether these protodyssomnias progress to true dyssomnias later on (2). Individualized bedtime habits such as reading or playing a quiet game can also help.
Circadian rhythm dyssomnias are characterized by inappropriate timing of sleep. This is more likely to occur in adolescence when bedtime is pushed back later. The teenager then tries to make up for the lost sleep by sleeping long periods during the weekend. Thus, this irregular sleep pattern leads to biologic clock disruption over time resulting in circadian rhythm dyssomnias characteristic of delayed sleep phase syndrome. This syndrome presents with an inability to sleep and wake at a customary time, excessive daytime sleepiness, and many naps with no difficulty in maintaining sleep once asleep. Diary/sleep logs reveal irregular sleep times, and MSLT is helpful in quantifying sleep debt. Treatment consists of eliminating sleep debt and reinforcing appropriate bedtime and rise time. When supportive or behavioral therapy fails, chronotherapy is indicated. Chronotherapy (phase delay treatment) allows the biological clock to reset by delaying sleep and rising times by 2 hours each day until the time of sleep onset is shifted back to a more reasonable hour.
Unlike dyssomnias in which the sleep process is disrupted, parasomnias represent behavioral intrusions upon ongoing sleep. These behaviors are caused by CNS arousal, especially activation of motor and autonomic components. Parasomnias are more likely to occur in males than females, and a patient suffering from one parasomnia is likely to exhibit another. For example, a child with sleep terror may also experience sleepwalking. Parasomnias can be divided into the following categories: arousal disorders, sleep-wake transition disorders, REM parasomnias, and other miscellaneous parasomnias.
Arousal disorders include sleep terror disorder and sleepwalking. Arousal disorders occur at transition from NREM stage 4 to REM sleep, which usually occurs 1-3 hours after sleep onset. Problems occur when this normally smooth transition is characterized by autonomic activity. In sleep terror, the child typically sits up, screams, and has a glassy, unseeing gaze associated with autonomic symptoms of palpitations, diaphoresis, and irregular breathing. This lasts for about 1 to 5 minutes until the child calms down and continues to sleep. A child in this condition is difficult to wake up and appears disoriented and confused when he does awaken. Unlike nightmares, the child does not recall the incident or any dreams in the morning (15,16). Sleepwalking may accompany sleep terrors and can be dangerous. The body movements that occur during sleepwalking are purposeless and uncoordinated. Locking the doors and windows and installing alarms that alert the parents when the child rises from bed are some of the safety measures (17).
Sleep lab studies may not be helpful since arousal disorders occur sporadically. Rather, having the parents videotape the episode of attack can be more diagnostic. As daytime stress and fatigue are known precipitators of arousal disorders, they should be avoided. Short naps can reduce NREM stage 4 sleep which reduces the likelihood of sleep terrors. Benzodiazepines can reduce numbers of attacks but drug tolerance develops. In severe cases or if the onset occurs in adolescence, it is important to rule out sleep-related seizures.
Sleep-wake transition disorders occur at transitions between sleep and waking. Examples of this category of parasomnias are rhythmic movements, nocturnal leg cramps, and sleep talking. Rhythmic movements include head banging, sleep starts (defined as sudden muscle jerks at sleep onset that may involve the limbs, neck, or entire body), and body rocking that usually occurs at sleep onset for <15 minutes duration. Prevalence decreases with age, and generally, measures to prevent self injury are sufficient.
Nightmares are by far the most common of REM parasomnias. Onset occurs at 3-6 years of age and up to 50% of this age group experience nightmares severe enough to worry their parents. Nightmares are terrifying arousals from REM sleep associated with anxious dream reports. Unlike sleep terrors, a child with nightmares can recall the event well in the morning. Also, nightmares typically take place in the last third of sleep when REM sleep dominates compared to sleep terror occurrences in the first 1-3 hours after sleep onset (NREM stage 4) (18). Treatment of nightmares mainly focuses on providing comfort and reassurance during the incident and reducing daytime stress. Withdrawal from certain medications such as beta-blockers and other drugs that suppress REM sleep (including tricyclic antidepressants and alcohol) can also trigger nightmares.
There are many other miscellaneous parasomnias. But the two most common ones in children are sleep bruxism and sleep enuresis. Sleep bruxism is stereotypic mouth movements in sleep that results in teeth grinding. Dentists are usually the first one to notice this problem. Bruxism is strongly related to stress and strained emotions. Management consists of dental interocclusal appliances (to prevent enamel wear), behavioral therapies, and night alarms. Sleep enuresis, or bed wetting, is diagnosed in the absence of urologic, medical, or psychiatric conditions in children after 5 years of age.
In studying sleep in the younger age groups, one should consider the age related differences in sleep stages and their implications. During the 1st year of life, REM sleep associated with arousals is dominant. Thus, infants are more likely to suffer from dyssomnias with sleep maintenance. During the preschool years, NREM stages predominate. Because NREM arousal parasomnias more often occur at the transition from deep to REM sleep, these sleep problems are more commonly seen in the preschool to primary school years and tend to disappear by teenage years. Adolescents, on the other hand, are more likely to be sleep deprived due to increasing workloads from school, sports, and social activities and events. The disruption of regularly sleep schedules and decrease in total amount of sleep predispose them to circadian rhythm dyssomnias.
Here is a summary outline of the sleep disorders discussed so far:
A. Dyssomnias
. . . . 1. Intrinsic dyssomnias
. . . . . . . . a. Breathing related sleep disorder
. . . . . . . . . . . . 1) Central (prematurity, Ondine's curse, etc.)
. . . . . . . . . . . . 2) Obstructive (large tonsils/adenoids, Pickwickian, Prader-Willi, etc.)
. . . . . . . . . . . . 3) Mixed
. . . . . . . . b. Narcolepsy
. . . . 2. Extrinsic dyssomnias
. . . . . . . . a. Infant protodyssomnia
. . . . . . . . b. Childhood insomnias (psychosocial and physiologic stress)
. . . . 3. Circadian rhythm disturbances (adolescents)
B. Parasomnias
. . . . 1. Arousal disorders
. . . . . . . . a. Sleep terrors
. . . . . . . . b. Sleep walking
. . . . 2. Sleep-wake transition phenomena
. . . . . . . . a. Sleep talking
. . . . . . . . b. Nocturnal leg cramps
. . . . . . . . c. Rhythmic movement disorders
. . . . 3. REM parasomnias
. . . . . . . . a. Nightmares
. . . . 4. Miscellaneous parasomnias
. . . . . . . . a. Sleep bruxism
. . . . . . . . b. Sleep enuresis
Disturbed sleep related to neurologic disorders can be due to diverse causes such as headaches, seizures, mental retardation, and cerebral degenerative disorders. The severity of the sleep problem is correlated to the extent of the neurologic conditions. Psychiatric problems can also lead to night time wakings, nightmares, or difficulty going to sleep. Examples are emotional trauma, stress, separation anxiety, attention deficit hyperactivity disorder, conduct disorder, and Tourette's syndrome. In older children, generalized anxiety disorder and major depression can play a role also. Thus, in assessing sleep disorders, the physician must distinguish between primary causes and sleep disturbances related to other medical or psychiatric disorders.
Questions
1. Which of the following helps to distinguish sleep terror from nightmares?
. . . . . a. Child does not recall the incident in the morning.
. . . . . b. Child is diaphoretic upon awakening.
. . . . . c. Common sleep disorder to occur in childhood.
. . . . . d. None of the above.
2. In which of the following cases would PSG (polysomnographic recordings) not be as helpful?
. . . . . a. Narcolepsy
. . . . . b. Sleep terror
. . . . . c. Sleep apnea
. . . . . d. a & b
3. Which of the following is NOT a primary sleep disorder?
. . . . . a. Tourette's syndrome
. . . . . b. Sleep bruxism
. . . . . c. Rhythmic movement disorder
. . . . . d. Protodyssomnia of infancy
4. Describe the clinical tetrad of narcolepsy?
5. Describe at least two causes of obstructive sleep apnea and two causes of non-obstructive sleep apnea?
6. Circadian rhythm dyssomnias typically occur in which age group?
References
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3. Pearce JW. Sleep disorders medicine. Lecture on 11/16/2001, University of Hawaii John A. Burns School of Medicine, Honolulu, HI.
4. Chokroverty S. Ch. 2-An Overview of Sleep. In: Chokroverty S (ed). Sleep Disorders Medicine: Basic Science, Technical Considerations, and Clinical Aspects, 2nd edition. 1999, Boston: Butterworth-Heinemann, pp. 8-9.
5. Ch. 3-Cardinal Manifestations, Pathophysiology, and Clinical Evaluation of Sleep Disorders: Classification of Sleep Disorders. In: Culebras A. Clinical Handbook of Sleep Disorders. 1996, Boston: Butterworth-Heinemann, pp. 84-86.
6. Parisi RA. Ch. 12-Respiration and Respiratory Function: Technique of Recording and Evaluation. In: Chokroverty S (ed). Sleep Disorders Medicine: Basic Science, Technical Considerations, and Clinical Aspects, 2nd edition. 1999, Boston: Butterworth-Heinemann, pp. 220-221.
7. Haddad GG. Ch. 375.2-Congenital Central Hypoventilation Syndrome (Ondine's Curse). In: Behrman RE, Kliegman RM, Jenson HB (eds). Nelson Textbook of Pediatrics, 16th ed. 2000, Philadelphia: W.B. Saunders Company, pp. 1250-1251.
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12. Ch. 6-Genetic Disorders. In: Cotran RS, Kumar V, Collins T. Robbins Pathologic Basis of Disease, 6th ed. 1999, Philadelphia: W.B. Saunders Company, pp. 180-181.
13. Magenis RE. Ch. 34: Chromosomes and their disorders. In: Goldman L, Bennett JC (ed). Cecil Textbook of Medicine, 21st ed. 2000, Philadelphia: W.B. Saunders Company, p. 149.
14. Curran JS, Barness LA. Ch. 43-Obesity. In: Behrman RE, Kliegman RM, Jenson HB (eds). Nelson Textbook of Pediatrics, 16th ed. 2000, Philadelphia: W.B. Saunders Company, p. 175.
15. Ch. 10-Parasomnias and Motor Disorders of Sleep: Arousal Disorders. In: Culebras A. Clinical Handbook of Sleep Disorders. 1996, Boston: Butterworth-Heinemann, pp. 314-315.
16. Cartwright RD. Ch. 7-Dreaming in Sleep Disordered Patients. In: Chokroverty S (ed). Sleep Disorders Medicine: Basic Science, Technical Considerations, and Clinical Aspects, 2nd edition. 1999, Boston: Butterworth-Heinemann, pp. 132-133.
17. Chokroverty S. Ch. 18-Approach to the Patient with Sleep Complaints. In: Chokroverty S (ed). Sleep Disorders Medicine: Basic Science, Technical Considerations, and Clinical Aspects, 2nd edition. 1999, Boston: Butterworth-Heinemann, p. 282.
18. Broughton RJ. Ch. 31-Behavioral Parasomnias. In: Chokroverty S (ed). Sleep Disorders Medicine: Basic Science, Technical Considerations, and Clinical Aspects, 2nd edition. 1999, Boston: Butterworth-Heinemann, pp. 640-641.
Answers to questions
1.a, 2.b, 3.a
4. Sleep attack, cataplexy, sleep paralysis, hypnagogic hallucinations
5. Obstructive: Tonsillar enlargement, Prader-Willi syndrome, Pickwickian. Non-obstructive: Prematurity, Ondine's Curse.
6. Adolescence