Sleepwalking or Somnambulism refers to recurrent episodes of abnormal, complex behavior that occurs during Slow Wave Sleep that is during the first third of the night during stages 3 and 4 of Non REM sleep.
The subject typically leaves the bed and is active in a confused and disoriented state, often moving slowly and clumsily, possibly with injury to themselves. The sleep walking may be preceded by a scream or occurrence of a Sleep Terror, with marked autonomic hyperactivity such as increased heart rate and respiratory rate. When occurring in a state of terror, the movements may be much more rapid, with episodes of rushing into walls, through windows and out into street. There is reduced responsiveness, but the subject may shout or scream. The flight response may include complex behavior such as starting a car and driving. The complex behaviour may be one of escape or of defense against a perceived threat. In some instances trying to stop the subject often leads to violent movements. Although there is amnesia of the event, the subject may have memory of the imminent danger or specific threats against themselves, family or property.
There is often a history of sleepwalking or night terrors in childhood and it is not uncommon for family members to be affected.
Sleepwalking is diagnosed through a combination of history and sleep studies including Actigraphy and PSG.