Parasomnias are undesirable physical events or experiences that occur during entry into sleep, within sleep, or during arousals from sleep. Parasomnias encompass abnormal sleep related movements, behaviors, emotions, perceptions, dreaming, and autonomic central nervous system functioning. Parasomnias are clinical disorders because of the resulting injuries, sleep disruption, adverse health effects, and untoward psychosocial effects. Parasomnias can affect the patient, bed partner, or both.
Parasomnias often involve complex seemingly purposeful and goal oriented behaviors which presumably performed with some personal meaning to the individual at the time, despite the logical and unsound nature of the behaviors injected outside the cautious awareness of the individual.
Differential Diagnosis of Nocturnal Events
| NREM
Parasomnia |
REM Behavior Disorder | Nocturnal Seizures | Psychogenic Events | |
| Time of Occurrence | First 1/3 of night | During REM; latter 2/3 of night | Any time
(most common during first 2 hours and last 2 hours of sleep) |
Anytime |
| Memory of Event | Usually none | Dream recall | Usually none but frontal lobe may have some recall | None |
| Stereotypical Movements | No | No | Yes | No |
| PSG Findings | Arousal from delta sleep | Excess EMG tone during REM sleep | Potentially epileptic activity | Occur from awake state |