Parasomnias are disorders of arousal or the interface between sleep and waking. Think of them as abnormal arousals. More precisely, they occur at the transitions between waking, NREM sleep, and REM sleep. Parasomnias may be induced or exacerbated by sleep but they are not disorders of the sleep stages as dyssomnias are.
Parasomnias include movements or behaviors that may impair sleep continuance, associated with sleep, sleep stages, or partial arousals from sleep. Parasomnias can be divided into four groups of disorders
These parasomnias encompass arousals with abnormal motor activity (i.e. uncontrollable violent behavior), behavioral experiences (i.e. sleep walking), or sensory experiences (i.e. dreamlike hallucinations). Parasomnias are more common in children; frequency decreases with age; the reported prevalence of parasomnias is approximately 4% in the adult population.
The arousal disorders usually occur in the first third of the night (when NREM is more common than REM).
Catathrenia (groaning during sleep) is sometimes called a parasmonia, although it could also be considered a feature of sleep-disordered breathing.
Trichotillomania - the impluse control disorder that causes people to pull their own hair out - has been proposed as a parasomnia - when the patient does it while asleep.
Although these undesirable physical and behavioral incidents and actions during sleep can be worrying and occasionally hazardous to the sleeper, you should remember that frequent or particularly dramatic parasomnias are diagnosable and treatable in most cases. The effective therapy in most cases is medication with long- or medium-acting benzodiazepine, such as clonazepam, taken at night before sleep.
Hallucinations – Many people occasionally experience a hallucination in conjunction with sleep (39%), although for half of those people it happens less than once a month. Hallucinations when falling asleep (hypnagogic hallucinations) are four times more common than when waking up (hypnopompic hallucinations).
Growing Pains? - An intriguing idea is that growing pains are a form of sleep disorder. Like parasomnias, they are relatively common in pre-school children and there appears to be a correlation with night terrors.
A compelling model of brain functioning involves the flip-flop switch, a systems engineering model of neural network functioning. Whether or not this model is accurate enough, it is clear just from observing people in day-to-day life, that nature gave us a “sleep-wake switch”. A person is either awake or asleep, not both at the same time or mixed – or at least that’s the way we think it should be. Parasomnias, however, represent a pathology of this switch. The sleep and wake states are not stable and waking seeps into sleeping time while sleep occasionally seeps into waking.
Another way to classify parasomnias is between NREM and REM disorders, depending on what type of sleep they arise from. When people wake up from NREM disorders they are confused; people who wake from REM are alert and can often remember their dreams. Reference
Parasomnias occur more frequently in kids than in adults. Indeed, over 80% of preschool-age children experience parasomnia events. Some pyschologists associate parasmonias in young (preschool) children with separation anxiety. There is a genetic predisposition for parasomnias, but specific genes and how they interact with the environment are not known.
The prevalence of parasomnias is estimated at 4% in the general adult population.
Treatments are behavioral and rarely pharmacological. Sometimes doctors feel no treatment is often preferable to available therapies because the symptoms are not severe, the disorders do not get worse or lead to other disorders, and the parasomnias that disappear over time are considered childhood issues because kids love them when they grow up. Further the science underlying the treatment of parasomnia is not as robust as some other medical treatments, perhaps because low incidences of the disorders means small sample sizes in trials and studies.
Experts generally warn against restraining sleepers in anticipation of confusional arousal, sleepwalking, or sleep terror. The bedroom should be made hazard-free to reduce risk of the person hurting anyone. Psychotherapy can often help reduce the incidence of these events, and sometimes patients are awoken right before their regular occurance of parasomnia to prevent it.
Pharmacological treatment is more common for the rare but serious conditions of REM Behavior Disorder and nocturnal eating disorders.
Epileptic seizures sometimes look like parasomnias - in particular like disorders of arousal from REM sleep. Both the subject’s family members who witness the symptoms first-hand and medical professionals making a first diagnosis are apt to make this mistake. The treatments for seizures (epileptic and otherwise) can involve powerful drugs, so it is important that an accurate diagnosis is made. Parasomnias are rarely dangerous enough to warrant drug therapy. Doctors have to distinguish between the two during diagnosis.
A polysomnogram can differentiate between the two. But there does seem to be a connection, if only through genetics. If a person has nocturnal frontal lobe epilepsy his or her family members are more likely to have parasomnias. Impairment in the cholinergic system seems to be behind both.