Parasomnias are a category of sleep disorders that involve abnormal movements, behaviors, emotions, perceptions, and dreams that occur while falling asleep, sleeping, between sleep stages, or during arousal from sleep. Most parasomnias are dissociated sleep states which are partial arousals during the transitions between wakefulness and NREM sleep, or wakefulness and REM sleep.
Non-rapid eye movement (NREM) parasomniasEdit
NREM parasomnias are arousal disorders that occur during stage 3 (or 4 by the R&K standardization) of NREM sleep—also known as slow wave sleep (SWS). They are caused by a physiological activation in which the patient’s brain exits from SWS and is caught in between a sleeping and waking state. In particular, these disorders involve activation of the autonomic nervous system, motor system, or cognitive processes during sleep or sleep-wake transitions.
Some NREM parasomnias (sleep-walking, night-terrors, and confusional arousal) are common during childhood but decrease in frequency with increasing age. They can be triggered in certain individuals, by alcohol, sleep deprivation, physical activity, emotional stress, depression, medications, or a fevered illness. These disorders of arousal can range from confusional arousals, somnambulism, to night terrors. Other specific disorders include sleepeating, sleep sex, teeth grinding, rhythmic movement disorder, restless legs syndrome, and somniloquy.
Confusional arousal is a condition when an individual awakens from sleep and remains in a confused state. It is characterized by the individual's partial awakening and sitting up to look around. They usually remain in bed and then return to sleep. These episodes last anywhere from seconds to minutes and may not be reactive to stimuli. Confusional arousal has a prevalence of 4% in adults, and is common in children. Infants and toddlers usually experience confusional arousals beginning with large amounts of movement and moaning, which can later progress to occasional thrashings or inconsolable crying. Confusional arousals are not considered dangerous. Another sleeping disorder may be present triggering these incomplete arousals.
Sleepwalking has a prevalence of 1%-17% in childhood, with the most frequent occurrences around the age of eleven to twelve. About 4% of adults experience somnambulism. Normal sleep cycles include states varying from drowsiness all the way to deep sleep. Every time an individual sleeps, he or she goes through various sequences of non-REM and REM sleep. Anxiety and fatigue are often connected with sleepwalking. For adults, alcohol, sedatives, medications, medical conditions and mental disorders are all associated with sleepwalking. Sleep walking may involve sitting up and looking awake when the individual is actually asleep, and getting up and walking around, moving items or undressing themselves. They will also be confused when waking up or opening their eyes during sleep. Some individuals also talk while in their sleep, saying meaningless words and even having arguments with people who are not there.
Sleep terrors (night terrors)Edit
Sleep terror is the most disruptive arousal disorder since it may involve loud screams and panic; in extreme cases, it may result in bodily harm or property damage by running about or hitting walls. All attempts to console the individual are futile and may prolong or intensify the victim’s confused state. Usually the victim experiences amnesia after the event but it may not be complete amnesia. Up to 3% of adults suffer from sleep terrors and exhibited behavior of this parasomnia can range from mild to extremely violent. This is very prevalent in those who suffer violent post-traumatic stress disorder (PTSD). They typically occur in stage 3 sleep.
Sleep sex, or sexsomnia, is a condition in which a person will engage in sexual acts while still asleep. A condition usually occupied by another sleep disorder it can include such acts as masturbation, fondling themselves or others, having sex with another person; and in more extreme cases, sexual assault (including rape).
Exploding head syndromeEdit
REM sleep behavior disorderEdit
REM sleep behavior disorder or RBD is the most common REM sleep parasomnia in which muscle atonia is absent. This allows the individual to act out their dreams and may result in repeated injury—bruises, lacerations, and fractures—to themselves or others. Patients may take self-protection measures by tethering themselves to bed, using pillow barricades, or sleeping in an empty room on a mattress. Demographically, 90% of RBD patients are males, and most are older than 50 years of age.
Typical clinical features of REM sleep behavior disorder are:
- Male gender predilection
- Mean age of onset 50–65 years (range 20–80 years)
- Vocalisation, screaming, swearing that may be associated with dreams
- Motor activity, simple or complex, that may result in injury to patient or bed-partner
- Occurrence usually in latter half of sleep period (REM sleep)
- May be associated with neurodegenerative disease 
Acute RBD occurs mostly as a result of a side-effect in prescribed medication—usually antidepressants. But if not, then 55% of the time the cause is unknown, while the other 45% of the time the cause is associated with alcohol.
Chronic RBD is idiopathic, meaning of unknown origin, or associated with neurological disorders. There is a growing association of chronic RBD with neurodegenerative disorders—Parkinson's disease, multiple system atrophy (MSA), or dementia—as an early indicator of these conditions by as much as 10 years.
Patients with narcolepsy also are more likely to develop RBD.
Recurrent isolated sleep paralysisEdit
Catathrenia, a rapid-eye-movement sleep parasomnia consisting of breath holding and expiratory groaning during sleep, is distinct from both somniloquy and obstructive sleep apnea. The sound is produced during exhalation as opposed to snoring which occurs during inhalation. It is usually not noticed by the person producing the sound but can be extremely disturbing to sleep partners, although once aware of it, sufferers tend to be woken up by their own groaning as well. Bed partners generally report hearing the person take a deep breath, hold it, then slowly exhale; often with a high-pitched squeak or groaning sound.
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