Elsevier

Epilepsy & Behavior

Volume 11, Issue 4, December 2007, Pages 483-491
Epilepsy & Behavior

Review
A review of sleepwalking (somnambulism): The enigma of neurophysiology and polysomnography with differential diagnosis of complex partial seizures

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Abstract

The goal of this report is to review all aspects of sleepwalking (SW), also known as somnambulism. Various factors seem to initiate SW, especially drugs, stress, and sleep deprivation. As an etiology, heredity is important, but other conditions include thyrotoxicosis, stress, and herpes simplex encephalitis. Psychological characteristics of sleepwalkers often include aggression, anxiety, panic disorder, and hysteria. Polysomnographic characteristics emphasize abnormal deep sleep associated with arousal and slow wave sleep fragmentation. In the differential diagnosis, the EEG is important to properly identify a seizure disorder, rather than SW. Associated disorders are Tourette’s syndrome, sleep-disordered breathing, and migraine. Various kinds of treatment are discussed, as are legal considerations, especially murder during sleepwalking.

Introduction

Sleepwalking (SW), also known as somnambulism, has been an enigma to neurophysiologists and polysomnographers, especially because complex motor behavior usually occurs during deep (stages 3 and 4) sleep [1]. The goal of this review is to describe all aspects of this condition and to try to understand how such complex behavior could emerge during deep sleep. Night terrors have been known to share a common genetic predisposition with SW and therefore, findings in one usually apply to the other [2].

Section snippets

Lithium

One of the earliest reports on SW was in 1979 when Charney et al. [1] stated that 9% of psychiatric patients on a combined lithium–neuroleptic treatment exhibited SW. As SW usually occurs during deep slow wave sleep, the increase in this stage of sleep caused by lithium could help to explain why this medication tended to increase SW. In this early study, the occurrence of seizures in two patients was considered unrelated to the somnambulistic episodes. Possible confirmation regarding lithium

Trauma (psychiatric)

After exploring SW in one patient by means of a pivotal dream, the investigator concluded that a severe traumatic experience in early childhood likely was the etiology of the SW [16].

Herpes simplex encephalitis

A 64-year-old man with herpes simplex encephalitis developed SW along with a memory disturbance. CT, MRI, and SPECT revealed lesions in the right temporal lobe [17].

Stress

In a report from the United Kingdom, the author emphasized that the constitutional basis for SW was beyond doubt, but that the actual expression may be

Clinical characteristics of sleepwalkers

An early description of patients with SW included the finding that sleepwalkers demonstrated high levels of psychopathology. Specifically, the patients showed active, outwardly directed behavioral patterns suggestive of difficulties in handling aggression [24].

Another study also emphasized aggression, in particular inhibited aggression, and an attitude characterized as a highly developed mental defense against anxiety, as determined by Rorschach tests [25]. Anxiety was emphasized in one other

Polysomnographic characteristics of sleepwalking

In an early study in 1995, SW was characterized as occurring during the first 3 hours of sleep when sleep stages 3 and 4 were most prevalent. The episodes were noted to last from 30 seconds to 30 minutes [32]. In another study, analysis showed decreased sleep efficiency and also stage 2 sleep, but increased stage 3 and 4 slow wave sleep. Also reported was an increase in the arousal index and wakefulness after sleep onset, and sleep fragmentation was concentrated mainly during stages 3 and 4.

EEG characteristics of sleepwalking

A very early study in 1978 on SW reported that theta activity from the temporal lobe was seen only with sphenoidal electrodes and not with routine scalp EEGs. Although the theta rhythm was not a sharp wave or spike discharge, the authors did raise the question of SW as a paroxysmal disorder from the temporal lobe [40]. A negative study in 1980 reported that waking EEGs were not helpful, and all-night records were needed if abnormalities were to be found [41]. On the other hand, another study

Differential diagnosis

As indicated in the previous section on EEG characteristics, the major differential diagnosis with SW is a seizure disorder, often called “episodic nocturnal wandering” [1], [32]. With long term video/EEG video, other groups have succeeded in differentiating sleepwalking from epilepsy [49], [50]. The clear evidence for an epileptic seizure, as opposed to SW, is the recording of rhythmical ictal patterns before the onset of and during the episode [46]. In addition to the recording of ictal

Pathogenesis

One early article in 1976 made an assumption that it was the corpus striatum that was involved in the overall coordination of stereotypic motor movements and, thus, possibly involved in SW [15]. One other report suggested a possible pathogenesis by assuming that the “dissociation between body sleep and mind sleep” arises from the activation of the thalamocingulate pathways with a persisting deactivation of other thalamocortical arousal systems [53]. The lack of full awareness and the amnesia

Tourette’s syndrome

In one report of 171 children, one-third had Tourette’s syndrome. Of the 13 identified as sleepwalkers, 10 also had Tourette’s syndrome. As 19% of the Tourette cases had SW and 8% of the children had SW, these data indicate only that there is a relationship between these two disorders, but the strength of the relationship cannot be easily determined. The conclusion was that this combination of SW and Tourette’s may be due to a disturbance of serotonin metabolism [54].

Sleep-disordered breathing

Abnormal respiratory events

Homicide or attempted homicide

As early as 1983, investigators reported that two sleepwalkers had episodes resulting in the deaths of three other individuals. Both sleepwalkers were employed, married, and functioning well without serious psychopathology, but the legal consequences were not made clear in this report [59]. Another case report described a 14-year-old boy who rose from his bed at 2:00 AM and savagely stabbed his 5-year-old cousin. The conclusion in this case was that the sleeping mind was not in touch with

Hypnosis

Four of six SW patients reported total alleviation of this parasomnia with the use of hypnosis [73]. In another report, subjects had severe somnambulism, but otherwise were free of psychiatric illness and responded well to six brief sessions of specialized hypnosis. Lasting improvement was noted 1 year later [74]. Of 27 adults with SW, 74% reported “much or very much improvement” with self-hypnosis practiced at home [75].

Anticipatory awakening

An 8-year-old boy was treated by awakening him for 5 nights just before

“Essence” of sleepwalking: A summary

Many different conclusions have been drawn to explain this intriguing phenomenon. They include a paroxysmal disorder of the temporal lobe [40], a disorder of abrupt arousal [48], a noninsane automatism [69], a dissociation between body sleep and mind sleep [49] and an abnormality in the neural mechanisms responsible for the regulation of slow wave sleep [34]. Also included was a phenomenon with a “protective dissociative mechanism, mobilized when intolerable impulses, feeling and memories

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