This article includes discussion of sleepwalking, nocturnal automatism, and somnambulism. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.
In this article, the author provides a review of sleepwalking disorder. Sleepwalking is a disorder of arousal with ambulation, and it usually originates from deep (N3) NREM sleep but can also arise out of N2 (37). Sleepwalking, like other disorders of arousal (DOA), is primed by conditions that increase the homeostatic sleep drive, such as sleep deprivation, and it is precipitated by conditions that lead to sudden arousal, such as obstructive sleep apnea. Many drug-induced sleepwalking cases occur after patients with restless legs syndrome (RLS) are treated with a sedative hypnotic medication. Patients with restless legs syndrome have difficulty falling asleep and are predisposed to nocturnal ambulation. Commonly prescribed sedatives, such as the benzodiazepine receptor agonists, when prescribed for sleep initiation in restless legs syndrome, may unleash complex sleepwalking behaviors, such as sleep related eating disorder.
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• Under normal conditions, arousals from deep slow-wave sleep (N3) are transient and result in either a return to NREM sleep or conversely, to a full transition to consciousness within seconds. Disorders of arousal occur when the brain fails to fully transition to sleep or wakefulness, resulting in behaviors that are amnestic and inappropriate.
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• Sleepwalking is a disorder of arousal with ambulation. These episodes are typically short-lived, lasting only a few minutes. However, prolonged episodes occur, especially in the setting of sedative hypnotic medications.
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• Patients with sleep initiation difficulties related to motor restlessness (restless legs syndrome) are commonly misdiagnosed as insomniacs and treated with sedative hypnotic medications. These hypnotic agents then prime patients predisposed to ambulation.
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• Sleepwalking is effectively treated by reversing conditions that promote sleep drive, such as sleep restriction, and treating conditions that lead to sleep fragmentation, such as sleep-disordered breathing.
Historical note and terminology
Reports from Hippocrates (c. 460-370 BCE), Aristotle (384-322 BCE), and Laertius (c. 200-300) allude to episodes that could be variously interpreted as sleepwalking, REM sleep behavior disorder, or nocturnal epilepsy. The Roman physician Galen (c. 129-200) wrote of spending an entire night sleepwalking only to be awoken after striking a stone (69).
Later, scholars began to speculate that sleepwalking may provide insights into brain and sleep function. During the Middle Ages, sleepwalking represented the emergence of primitive behaviors that only occurred once the rational and afferent functions of the brain were deactivated during sleep (45). During the Renaissance, sleepwalking was a window into psychological conflict. Most notably, in William Shakespeare’s Macbeth, sleepwalking Lady Macbeth admits to being a co-conspirator in murder.
Sleepwalking understood as a behavioral manifestation of dreaming ended in the mid-20th century with the discovery of the ultradian (NREM/REM) sleep cycle. It was noted that sleepwalking did not arise out of intensive dream sleep (REM), but instead out of predominantly deep NREM sleep (08). In 1986, REM sleep behavior disorder was reported, revealing the coexistence of a disorder of dream enactment (61). After recognizing the normal ultradian alternations between sleep and wakefulness (every 90 minutes), researchers found periodic cortical arousals every 30 to 90 seconds in NREM sleep (the cyclic alternating pattern). That sleep was not a homogenous state of unconsciousness, but instead had frequent, non-pathological arousals and awakenings was a breakthrough in understanding parasomnias (05).
Over the last two decades, reports of complex amnestic nocturnal behaviors have risen in parallel to the widespread use of sedative medications, most notably the benzodiazepine receptor agonists (BRAs) (15; 66). These cases commonly occur in the setting of often unrecognized restless legs syndrome (30).
Sleepwalking episodes captured during polysomnography investigation reveal a transition to wake-like cortical activity on scalp EEG. This finding confirms that the name “sleepwalking” is misleading and that these behaviors are more appropriately understood as disorders of arousal with ambulation. Thus, the International Classification of Sleep Disorders, 3rd edition (ICSD-3) lists sleepwalking, along with confusional arousals and sleep terrors, as disorders of arousal (01).
Table 1. Diagnostic Criteria for Disorders of Arousal from Non-Rapid Eye Movement sleep-Sleepwalking (ICSD-3)
General criteria (A to E must be met)
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A. Recurrent episodes of incomplete awakening from sleep
B. Inappropriate or absent responsiveness to efforts of others to intervene or redirect the person during the episode
C. Limited or no associative cognition or dream imagery
D. Partial or complete amnesia for the episode
E. The disturbance not better explained by another sleep disorder, mental disorder, medical condition, medication, or substance
Sleepwalking specific criteria (A and B must be met)
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A. The disorder meets general criteria for NREM disorders of arousal
B. The arousals are associated with ambulation and other complex behaviors out of bed