Excerpt from Somnambulism (Sleep Walking)

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Background

Somnambulism (ie, sleepwalking) is a disorder of arousal that falls under the parasomnia group. Parasomnias are undesirable motor, verbal, or experiential events that occur during sleep. These phenomena occur as primary sleep events or secondary to systemic disease. They are categorized as those occurring in rapid eye movement (REM) sleep; those occurring during non–rapid eye movement (NREM) sleep; and miscellaneous types that do not relate to any specific sleep state.

Pathophysiology

The parasomnias have been thought to represent not pathologic cerebral functioning but rather a response to CNS activation that results in sleep-wake or REM-NREM state confusion, instability, or overlap. Recent studies, however, demonstrate differences between sleep patterns and neuronal sleep control mechanisms in individuals with parasomnias compared with those without. Normal sleep involves cyclic hypnic patterns throughout the night between wakefulness, NREM, and REM states. The CNS remains active during all sleep-wake states, although rapid changes are required in neural networks, rhythms, and neurotransmitters with state changes. The length of each cycle averages 50 minutes for a full-term newborn, increasing to approximately 90 minutes by adolescence.

Slow wave sleep (SWS) normally occurs in the first 2 hypnic cycles; younger children have an additional SWS period toward the end of the sleep period. Children typically enter their deepest sleep within 15 minutes of sleep onset, and this first SWS period lasts from 45-75 minutes. This explains why it is easy to move children without rousing them soon after sleep onset. Parasomnias occur as children are caught in a mixed state of transition from one sleep cycle to the next (eg, NREM-wakefulness). This transition state is characterized by a high arousal threshold, mental confusion, and unclear perception.

Sleepwalkers appear to have an abnormality in slow wave sleep regulation. The dissociation that occurs between body and mind sleep appears to arise from activation of thalamocingulate pathways with persisting deactivation of other thalamocortical arousal systems. The first slow wave sleep period of the night is considered to be more disturbed in somnambulistic individuals, and the entire NREM-REM sleep cycle is more fragmented. Because these disorders occur more frequently in children, these differences have been suggested as signs of CNS immaturity.

Frequency

United States

Disorders of arousal are all more prevalent in children than adults. Confusional arousals are reported in 5-15% of children. Sleep terrors have an incidence of approximately 1%.

International

In Sweden, the incidence of quiet sleepwalking is reported as 40% with a yearly prevalence of 6-17%. Only 2-3% report more than 1 episode per month, and 33% report only a single episode.

In a survey of adults in the United Kingdom, 2.2% reported having night terrors, 2.0% reported sleep walking, and 4.2% reported confusional arousals.

Mortality/Morbidity

The NREM parasomnias are rarely associated with any significant morbidity, although children can strike objects during sleepwalking and occasionally become injured. Sleep-disordered breathing and, to a lesser extent, restless legs syndrome have been associated in children, although with less frequency than reported in adults. The incidence of associated sleep disorders has been reported to be as high as 61%.

Morbidity in adolescents and adults may be more significant. More complex motor behaviors such as driving a car, cooking, eating, or playing a musical instrument have been reported. Injurious behaviors to the patient and/or bed partner may be associated with forensic medicine implications. An increased incidence of psychiatric disorders such as neuroses, panic disorder, phobias, and suicidal ideations has been reported in both these groups. Sleep-disordered breathing, including a sense of choking or blocked breathing, has also been reported. The respiratory events may have a deleterious effect on sleep by increasing arousals and sleep fragmentation.

Race

No racial predilection is known.

Sex

Sleepwalking and confusional arousals have an equal incidence in males and females. Sleep terrors are more common in boys.

Age

Sleepwalking occurs most commonly in middle childhood and preadolescence, with a peak incidence in children aged 11-12 years. Confusional arousals are most common in toddlers and preschool-aged children. Sleep terrors occur most commonly in children aged 4-12 years.

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