Healthy sleep is characterized by complete rest, interrupted only by occasional changes in body position.
In the transition to abnormal, disturbing or potentially harmful behaviors such as sleepwalking, teeth grinding (bruxism), muscle spasms, etc., various movements, twitching, vocalizations or sensations occur in otherwise healthy persons, and it is not clear from the outset whether they are being caused by a disease (e.g. epilepsy) or whether they are so-called normal variants. Often overnight observation in the sleep laboratory is needed to correctly understand the nature of such phenomena. The classification is mainly based on the stage of sleep in which the phenomenon occurs.
In the transition from wakefulness to sleep, as well as in superficial sleep, harmless twitching when falling asleep, stereotyped rhythmic body movements (rolling movements, hitting head on pillow), sudden popping sounds (exploding head syndrome), talking, moaning (catathrenia), teeth grinding, muscle spasms during sleep, sleep paralysis, or hypnagogic hallucinations all occur frequently.
In deep sleep, many healthy people and especially patients with restless legs syndrome display so-called periodic leg movements during sleep (PLMS), which can rarely also lead to daytime sleepiness. In case of sporadic twitching of the face or head (neck myoclonus), which can lead to back pain in rare cases, epileptic seizures also need to be excluded. During deep sleep, sleepwalking occurs in individuals genetically predisposed to this, especially when the sleeper is awakened from deep sleep. More common than full-blown sleepwalking inside or even outside the room is “confusional awakening“, in which the affected person sits up in bed, looks around with a blank stare, possibly mumbles something, and then slowly lies down again and continues to sleep.
In REM sleep, we experience the most vivid dreams that most sleepers can remember. Nightmares are filled with fearful content and continue to preoccupy the dreamer after awakening. A specific type of nightmares, usually with fighting content, is accompanied by strong movements or screaming and thrashing around. This so-called dream-sleep behavior disorder may be a symptom of incipient dementia or Parkinson’s Disease. However, similar behaviors also occur in chronic alcoholism or narcolepsy- cataplexy.
