Intrinsic Dyssomnias

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The two intrinsic dyssomnias that most commonly affect children and adolescents are both disorders of excessive somnolence: obstructive sleep apnea syndrome and narcolepsy. In the former, children may be sleepy during the daytime because of the multiple brief obstructive apneas that arouse them repeatedly from sleep. Over time, they become significantly sleep deprived and show compensatory daytime sleepiness. In narcolepsy, irresistible attacks of REM sleep interrupt wakefulness.

Sleep Apnea Syndromes

A sleep apnea event is an interruption of breathing during sleep that exceeds 10 seconds; a hypopnea is a period of reduced ventilation below 50% of waking ventilation (Krieger 1990). Sleep apnea syndromes are characterized by an apnea index greater than 5 apneas or 10 apnea/hypopnea combinations per hour of sleep. Apneas can last from 10 seconds to 3 minutes, usually having a duration of 30-40 seconds. Three types of sleep apneas have been described (Guilleminault and Ariagno 1989):

1. Obstructive sleep apnea is characterized by persistent diaphragmatic respiratory movements without passage of air through a hypopharyngeal-glottal obstruction.
2. Central sleep apnea is characterized by absent respiratory movements and no airflow.
3. Mixed sleep apnea begins with no observable respiration or airflow followed by vigorous thoracic and abdominal efforts to move air against an obstructed glottis.

Apneas may be triggered by immaturities or dysfunction of the respiratory center (central apneas) or by collapse of the airway so that glottal airflow is regularly obstructed during sleep (obstructive apneas). In children, obstructive sleep apnea syndrome may result from mechanical obstruction of the upper airway related to enlarged tonsils and adenoids or to excessive obesity; central apneas may be related to medical and neurological conditions of the lungs or of the respiratory control systems in the central nervous system.

When apneas occur during sleep, blood and brain oxygen saturation may fall to dangerous levels. A brief arousal to waking restores breathing and oxygenation, and the subject then returns to sleep. The arousal is most often a microarousal, lasting 1-2 seconds, too short to be remembered by the sleeper in the morning. Microarousals after sleep apneas may recur 200-300 times nightly in serious disorders. Because of the cumulative loss of sleep, these children may present with symptoms of daytime sleepiness, chronic fatigue, and cognitive and attention deficits. The presenting complaint may be deteriorating school performance. Sometimes children do not recognize or acknowledge their sleepiness; rather, they react by fidgeting and squirming to “fight” sleepiness to remain awake. Such children may be mistakenly identified by teachers and professionals as having attention-deficit/hyperactivity disorder (ADHD). When the multiple awakenings from sleep at night also interrupt the normal secretion of growth hormone during Stage 4 NREM sleep, a child may present initially with mild growth retardation or, in extreme cases, a full-blown failure-to-thrive syndrome. In other words, all children who present with ADHD or a failure-to-thrive syndrome should be evaluated for possible obstructive sleep apnea syndrome.

Sleep apnea must be investigated by polysomnography in a sleep laboratory. Only this technique provides an accurate description of the type of apnea episode and its association with REM or NREM sleep. The degree of oxygen desaturation, the presence of secondary cardiac arrhythmias, and the amount of sleep fragmentation (arousal) are further indicators of the severity of the condition. Another diagnostic procedure, the Multiple Sleep Latency Test (MSLT), may be indicated. This test is a standardized daytime polysomnographic procedure that attempts to elicit daytime naps at regular intervals so that the amount of daytime sleepiness or sleep debt that has accumulated can be assessed.

Until recently, medical practice in the United States advocated the routine removal of children’s tonsils and adenoids. With a change in practice patterns over the past two decades, obstructive sleep apnea syndrome has become common, although epidemiological data are not available. Characteristically, children with this syndrome are referred for fragmented sleep, mouth breathing and snoring during sleep, daytime fatigue, or daytime ADHD. A careful history confirms the symptom of noisy breathing. When questioned, parents may also recognize a verbal description of “stopped” breathing during sleep. The physical examination may reveal hypertrophied tonsils, but retropharyngeal adenoidal enlargement is not always obvious without a more formal ear, nose, and throat evaluation. Surgical removal of obstructing tonsils and adenoids usually is curative. Occasionally, regeneration of obstructive tissue postoperatively necessitates a second surgical intervention. Children with craniofacial abnormalities are likely to have obstructive sleep apnea syndrome that does not respond to tonsil and adenoid surgery. Other surgical treatments for severe, refractory cases include uvulopalatopharyngoplasty, mandibular and maxillary advancement, and tracheostomy.

RELATED STORIES:
Daytime Sleepiness   REM Parasomnias   Sleep-Wake Transition Disorders   Classification of Sleep Disorders   General Evaluation of Childhood Sleep-Wake Disorders   Dyssomnias   Narcolepsy   Circadian Rhythm Dyssomnias in Adolescence   Disorders of Arousal   Developmental Aspects of Sleep-Wake Organization

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