Sleep Paralysis

Excerpt

Sleep paralysis refers to the phenomenon in which resumption of consciousness occurs while muscle atonia of REM (rapid eye movement) sleep is maintained, leading to intense fear and apprehension in the patient as the patient lies awake without the ability to use any part of their body. It is often accompanied by visual hallucinations of the intruder and incubus variety. Intruder hallucinations involve the perception of a dangerous person or presence in the room. The Incubus phenomenon is characterized by a hallucination with a feeling of pressure on the thorax while carrying out aggressive and/or sexual acts. It tends to be accompanied by anxiety, paralysis, and feelings of suffocation.

The usual phase of the sleep cycle in which it manifests is the REM sleep phase. During Non-REM sleep, there is an increase in parasympathetic tone and a decrease in sympathetic tone, while during phasic REM sleep, there are surges in sympathetic tone. It prevents movement of body parts in response to the dreams and muscles of the body become paralyzed temporarily. If the patient achieves wakefulness in this state, it creates the dissociation between perception and motor control that is characteristic of sleep paralysis.