A History of Sleepwalking
Pondered by Galen, Hippocrates, and Shakespeare, sleepwalking has piqued the interest of thinkers for millennia. And though the condition is often benign, sleepwalking can signal a more serious underlying medical problem that should be addressed. Medscape recently spoke with Michael J. Howell, MD, director of the Sleep Medicine Fellowship in the Department of Sleep Medicine at Minnesota Regional Sleep Disorders Center in Minneapolis, about the causes and consequences of sleepwalking, along with possible management strategies.
Medscape: When was sleepwalking first described?
Michael Howell, MD: There have been descriptions since the time of Hippocrates, Aristotle, and Galen. Probably the most famous description of a sleepwalker is Lady Macbeth, in The Tragedy of Macbeth by William Shakespeare. What he clearly describes is a sleepwalker who is dreaming. She is parading around and acting out the subconscious conflict that came from having murdered King Duncan, if I remember the play correctly.
It's hard to confirm whether these early accounts are actually talking about sleepwalking—which is a confusional arousal that tends to come out of non-rapid eye movement (NREM) sleep—or dream enactment, which is a different condition arising out of REM sleep that tends to be more intense and include violent thrashing, punching, and kicking. Some variation of these abnormal behaviors have been described for a very long time.
Medscape: When did the more recent understanding of sleepwalking arise?
Dr Howell: Quite frankly, we don't know a lot about sleepwalking in particular. We know a lot more about seizure disorders and REM sleep behavior than we know about sleepwalking, in terms of the underlying brain processes that are triggering the underlying pathophysiology.
It's worthwhile to remember that our understanding of sleep as being a rather diverse condition that cycles through various stages is really a revolutionary concept from just the past 50 years. Before that, sleep had many different interpretations, from religious explanations to ideas that the brain was in an idling state.
It was Nathaniel Kleitman at the University of Chicago in the late 1940s and early 1950s who recognized that we go through these cycles, and there are times when the brain is extremely active at night and we dream most vividly. Subsequently, seminal research done in the 1960s by Dr Roger Broughton revealed that sleepwalking occurs during NREM sleep rather than during REM sleep, as was previously assumed.
Separating Sleepwalking From Related Conditions
Dr Howell: For a long time, it was primarily thought that sleepwalking was essentially dream enactment, which is not true at all. Again, sleepwalking is a disorder of arousal that comes out of non-REM, typically slow-wave sleep. It is an odd mixture of both sleep and wakefulness. The term is actually a bit of a misnomer, in that if you look at the brainwaves of somebody who's sleepwalking on EEG, most of them actually look like wakefulness.
If you really bore down and take a look at it, sleepwalking people have a little bit slower activity in their the frontal lobes, the executive prefrontal cortex, and areas that control judgment, which make a lot of sense. Functional imaging studies show that they also have sleep-like activity in memory areas of the brain, namely the hippocampus. It makes a lot of sense that if somebody was sleepwalking, they'd have areas of the brain—motor areas and visual pathways—that are wide awake, so that they'll avoid obstacles. They'll go up and down the stairs without falling, the vast majority of times.
Medscape: So people sleepwalk with their eyes open?
Dr Howell: Yes. If you don't really pay close attention to a sleepwalker, or if you didn't know them and that they probably are not up and going to the kitchen at 2:00 AM, you'd probably just assume they were awake.
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Cite this: Sleepwalking: The Science, Cures, and Consequences - Medscape - Jul 26, 2016.