Sleep paralysis consists of a period of inability to perform voluntary movements either at sleep onset (called hypnogogic or predormital form) or upon awakening (called hypnopompic or postdormtal form). Sleep paralysis may also be referred to as isolated sleep paralysis, familial sleep paralysis, hynogogic or hypnopompic paralysis, predormital or postdormital paralysis What are the symptoms? * A complaint of inability to move the trunk or limbs at sleep onset or upon awakening * Presence of brief episodes of partial or complete skeletal muscle paralysis * Episodes can be associated with hypnagogic hallucinations or dream-like mentation (act or use of the brain) Sleep paralysis is most often associated with narcolepsy, a neurological condition in which the person has uncontrollable naps. However, there are many people who experience sleep paralysis without having signs of narcolepsy. Sometimes it runs in families. There is no known explanation why some people experience this paralysis. It is not harmful, although most people report feeling very afraid because they do not know what is happening, and within minutes they gradually or abruptly are able to move again; the episode is often terminated by a sound or a touch on the body.