Somnambulism

Sleepwalking
John Everett Millais, The Somnambulist, 1871
Classification and external resources
Specialty	Psychiatry, Sleep medicine
ICD-10	F51.3
DiseasesDB	36323
MedlinePlus	000808
eMedicine	article/1188854
MeSH	D013009
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Sleepwalking, also known as somnambulism or noctambulism, is a phenomenon of combined sleep and wakefulness. It is classified as a sleep disorder belonging to the parasomnia family. Sleepwalking occurs during slow wave sleep stage in a state of low consciousness and perform activities that are usually performed during a state of full consciousness. These activities can be as benign as sitting up in bed, walking to a bathroom, and cleaning, or as hazardous as cooking, driving, violent gestures, grabbing at hallucinated objects, or even homicide.

Although sleepwalking cases generally consist of simple, repeated behaviours, there are occasionally reports of people performing complex behaviours while asleep, although their legitimacy is often disputed. Sleepwalkers often have little or no memory of the incident, as their consciousness has altered into a state in which it is harder to recall memories. Although their eyes are open, their expression is dim and glazed over. Sleepwalking may last as little as 30 seconds or as long as 30 minutes.

Sleepwalking occurs during slow-wave sleep (N3) of non-rapid eye movement sleep (NREM sleep) cycles. Sleepwalking typically occurs within the first third of the night when slow wave sleep is most prominent. Usually, if sleepwalking occurs at all, it will only occur once in a night.

Three common diagnostic systems that are generally used for sleepwalking disorders are International Classification of Diagnoses, the International Classification of Sleep Disorders 3, and the Diagnostic and Statistical Manual.Polysomnography is the only accurate measure of sleepwalking. Other measures commonly used include self-report (e.g.), parent (e.g.), partner or house-mate report.

Sleepwalking should not be confused with alcohol- or drug-induced blackouts, which can result in amnesia for events similar to sleepwalking. During an alcohol-induced blackout (drug-related amnesia), a person is able to actively engage and respond to their environment (e.g. having conversations or driving a vehicle), however the brain does not create memories for the events. Alcohol-induced blackouts can occur with blood alcohol levels higher than 0.06g/dl. A systematic review of the literature found that approximately 50% of drinkers have experienced memory loss during a drinking episode and have had associated negative consequences similar to sleepwalkers, including injury and death.

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