Intrinsic Dyssomnias

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.