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Review Article
Indian J Med Res 131, February 2010, pp 333-337
Parasomnias: an overview
Greg Matwiyoff & Teofilo Lee-Chiong
Division of Sleep Medicine, Department of Medicine, National Jewish Health, Denver, Colorado, USA
Received December 29, 2008
Parasomnias are abnormal experiences or behaviours that occur during sleep and can be subdivided
into disorders of arousal, disorders of rapid eye movement (REM) sleep or other parasomnias. Diagnosis
rests on a thorough clinical evaluation with supporting data from a full polysomnography with time
synchronized video. While the prognosis for arousal disorders is generally excellent, the diagnosis of
REM behaviour disorder (RBD) is more ominous and associated with neurodegenerative disorders, and
as such, requires routine neurological surveillance. The cornerstone of treatment for all parasomnias is
adequate patient and bed partner education. Data supporting pharmacologic therapy are limited but
clonazapam for RBD has been reported to be effective in up to 89 per cent of patients.
Key words Confusional arousal - nightmares - parasomnias - REM - sleep behaviour disorder - sleep walking - sleep terror
Parasomnias constitute one of the main categories
of sleep disorders. Broadly defined these are undesirable
behaviour or experiential phenomena occurring
during sleep or in the transition to, and from, sleep.
Parasomnias can be divided into three subgroups:
disorders of arousal, disorders of REM sleep, and
other parasomnias. These occur due to abnormal
transitions between the three primary states of being
wake, rapid eye movement (REM) sleep, and non rapid
eye movement (NREM) sleep. These different states
may overlap or intrude into one another, and it is the
overlap of wakefulness and NREM sleep that gives
rise to confusional arousals, and the intrusion of REM
sleep into waking that produces REM sleep behaviour
disorder (RBD).
equally important disorders, such as exploding head
syndrome, sleep-related groaning (catathrenia) and
sleep-related eating disorder will be discussed briefly.
Disorders of arousal
Non rapid eye movement sleep arousal parasomnias
include confusional arousals, sleep terrors (pavor
nocturnus) and sleepwalking (somnambulism). These
emerge when normal wake and NREM state boundaries
become destabilized and elements of the waking state
intrude into NREM sleep.
Confusional arousals can occur throughout the night
but are seen most commonly during the first half of the
major sleep period when NREM density is highest.
Confusional arousals are estimated to affect 4 per cent
of adults. It is characterized by abrupt awakenings with
apparent confusion, diminished vigilance, disorientation,
and occasional violent or inappropriate behaviour.
Children may present with inconsolable crying1. The
Parasomnias most likely to be encountered in
clinical practice are namely, sleepwalking, sleep terrors,
confusional arousals, REM sleep behaviour disorder
(RBD) and nightmares. In addition, less common, but
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duration of arousals is variable but can last from several
minutes to hours. Affected individuals often have no
recollection of the event upon awakening, and typically
do not leave the bed2,3.
Sleep terrors are characterized by abrupt awakenings
from sleep accompanied by loud screaming, crying,
apparent panic and agitation2. Individuals may also
demonstrate violent behaviour, and attempts to reason
with, or console, are often unsuccessful. Indeed, the
latter may even give rise to worse behaviour or a violent
reaction2,4. Sleep terrors are believed to be a reaction to
a frightening image that results in agitated arousal and
sympathetic nervous activation2.
During an episode of sleepwalking, a person may
appear agitated or calm, and behaviour may range
from simple ambulation with a “glassy stare” to more
complex activities such as driving5. Sleepwalking may
be preceded by confusional arousals or sleep terrors2,3.
Sleepwalking occurs more frequently in children with
an estimated prevalence of up to 40 per cent in this age
group. Prevalence among adults is about 4 per cent1,6.
Evaluation of individuals with arousal disorders
begins with a thorough history and physical
examination, emphasizing personal and family
history of sleep disorders and social history. Inquiry
should include a search for factors that may trigger or
exacerbate the parasomnias including febrile illness,
alcohol use, sleep deprivation, stressors and medication.
A neurologic and mental status examination is essential.
Certain individuals may require additional testing,
particularly those who present with occupationally- or
socially-limiting excessive daytime sleepiness; violent
or disruptive behaviour; injuries to self or others;
or significant medical, psychiatric or neurologic
findings. In such cases, an attended polysomnographic
evaluation with time-synchronized video monitoring
may help identify nocturnal behaviours associated with
an arousal disorder. Additional studies include full
montage electroencephalography to exclude nocturnal
seizures as well as neuroimaging studies to exclude a
structural lesion.
Differential diagnoses is extensive and include
sleep-related breathing disorders, RBD, psychiatric
disorders, nocturnal seizures, medication or
substance use (e.g., alcohol, benzodiazepines and non
benzodiazepine benzodiazepine receptor agonists)7 and
malingering.
The primary therapy for disorders of arousal is
reassurance and prevention. For most, the disease course
is usually benign and tends to resolve spontaneously
with time. It is essential that both the patient and bed
partner be educated about safety precautions for the
home and bedroom environment, such as reducing or
eliminating potential sources of injury (e.g., relocating
the bedroom to a room on the ground floor, securing
doors, using heavy draperies over the windows,
removing mirrors, and keeping the floor free of objects
that the sleepwalker might potentially trip over). Bed
partners should be counselled not to attempt to stimulate
the patient during an episode as this may trigger
violent behaviour2. Additional preventive measures
include avoidance of factors and behaviours that
can precipitate arousal parasomnias, including sleep
deprivation as well as the use of alcohol and caffeine.
A trial of sleep extension or scheduled awakening
may be considered. With scheduled awakening, the
patient is awakened just before the typical time of the
parasomnia episode and thereafter allowed to return to
sleep. Pharmacologic agents that have been used with
some success include paroxetine and trazodone and
low-dose benzodiazepines8,10. Relaxation techniques
and hypnosis have been described as therapy for
NREM arousal disorders11,12.
REM sleep behaviour disorder (RBD)
REM sleep is defined by a low amplitude mixed
frequency electroencephalographic tracing. There is
variability in resting heart and respiratory rate, as well
as increased metabolism and body temperature relative
to the NREM state. Finally, REM sleep is further
characterized by a paucity of muscle activity with near
complete somatic muscular atonia and little to no chin
or leg electromyographic activity.
REM sleep behaviour disorder is characterized by
the intermittent loss of REM atonia due to disinhibition
of normally inhibitory mid-brain projections to spinal
motor neurons. This, in conjunction with an active
dream state, results in behavioural release and the
apparent “acting out of dreams”. The Table provides
the key characteristics of NREM arousal disorders and
RBD.
Prevalence of RBD is estimated to be about 0.5
per cent13. RBD tends to affect older adults, with
a mean age of onset of 50 to 60 yr, predominantly
affecting males13. It may be a harbinger of significant
neurodegenerative disorders, including Parkinson’s
disease (PD) as well as other synucleinopathies. Up to
25 per cent of patients with PD demonstrate clinical
features of RBD. Conversely, PD may develop in up
Matwiyoff & Lee-chiong: Parasomnias: an overview
335
Table. Features of NREM disorders of arousal and REM sleep behaviour disorder
NREM disorders of arousal
REM sleep behaviour disorder
Adolescence and young adult
Late middle age
(mean age 59.3 yr)
Clinical course
Usually benign and may decrease with age
May be harbinger of Parkinson’s disease or
other neurodegenerative diseases
Episode recall
Usually none
Often awakens completely aware
Complex motor activity
Yes
Yes
Sleep stage association
NREM first half of night
REM second half of night
Gender
Male=Female
Predominantly male (90%)
NREM, non rapid eye movement
Characteristic
Age of onset
to 43 per cent of patients diagnosed with RBD14,15.
Other disease processes associated with RBD include
narcolepsy (reported in 25% of patients with RBD),
multiple sclerosis, Tourette’s syndrome, and normal
pressure hydrocephalus15.
REM behaviour disorder may present with
complaints by patients or bed partners of violent
nocturnal behaviour especially when the latter are out
of character with the patient’s waking personality. The
patient may complain of vivid dreaming and self or
bed partner injury. Abnormal behaviours include sleep
talking, yelling, limb movement, and complex motor
activities. Patients with RBD arouse from sleep to full
alertness often with complete recall of fearful dream
content, which may involve being chased or attacked.
The motor behaviour exhibited tends to correlate with
dream content. The frequency of these episodes varies
from once every few weeks to several times a night.
Episodes tend to occur 90 min or more after sleep
onset, when the first REM period typically begins. As
the REM density is greatest during the latter part of the
evening, RBD episodes tend to occur more frequently
during this time.
Differential diagnostic considerations include the
NREM arousal disorders, atypical arousals arising from
patients with obstructive sleep apnoea and periodic
limb movement disorder; nocturnal seizures; panic
disorder; and dissociative disorder.
Evaluation of patients with suspected RBD includes
a thorough medical, neurologic and psychiatric history,
and physical examination as well as polysomnography
with video monitoring. Polysomnographic findings
often reveal normal sleep architecture and characteristic
REM-associated abnormalities (increase in chin EMG
activity, and excess REM-associated limb activity)16.
Treatment of RBD involves ensuring the safety of
the patient and bed partner. Pharmacologic treatment
with benzodiazapines is reported to be quite effective
with one study demonstrating an 89.5 per cent
effectiveness with clonazapam17. Other studies have
described some success with melatonin, pramiprexole,
levodopa, gabapentin and clonidine18-24, but further
investigations are required before these agents become
standard therapies for this disorder.
Nightmares
Nightmares are unpleasant, often frightening,
dreams that commonly awaken the sleeper out of
REM sleep3. Episodes typically occur in the latter half
of the night. Following the awakening, the individual
becomes fully alert and profoundly anxious. There is
vivid recall of the preceding dream as well as difficulty
returning to sleep. Compared to sleep terrors, there
is less autonomic activation, and tachycardia and
tachypnoea, if present, are not as severe. Nightmares
related to acute stress disorder or post-traumatic stress
disorder can also occur during NREM sleep.
Episodes can be precipitated by illness, traumatic
experiences, and alcohol and medication use, such as
antidepressants and beta-antagonist antihypertensive
agents. Onset of nightmares is usually during childhood
when prevalence is highest. Among adults, nightmares
appear to be more common in women than in men.
Nightmares should be distinguished from sleep
terrors, RBD and nocturnal panic attacks. Aside from
reassurance that the condition is benign, no specific
therapy is usually necessary. Behavioural treatment,
such as imagery, psychotherapy or REM sleep
suppressant agents may be considered for individuals
who present with very frequent events or who describe
extremely disturbing dream contents.
Other parasomnias
The exploding head syndrome consists of a
sensation of sudden loud noise or “explosion” felt in the
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head that occurs as an individual falls asleep. It is not
accompanied by significant pain but may be associated
with a sensation of a flash of light or a myoclonic jerk.
This disorder is considered by many to be a variant
of sleep starts and generally has a benign course that
requires no specific therapy3.
Sleep-related groaning, or catathrenia, is
characterized by expiratory groaning during sleep,
commonly during REM sleep in the second half of
the night. It is a rare condition that is more prevalent
among males. Affected individuals are asymptomatic
and physical examination and sleep architecture are
generally normal3.
Finally, sleep-related eating syndrome consists of
arousals from sleep with involuntary eating or drinking.
The awakenings appear to be triggered by learned
behaviour and not by real hunger or thirst. There is
generally partial or total amnesia for the episode, and
no associated abnormal eating behaviour while awake.
Onset is commonly during adulthood, with women
affected more frequently than men. Episodes can be
precipitated by sleepwalking, obstructive sleep apnoea
and medication use (e.g., zolpidem).
Summary
In summary, diagnosis of parasomnias relies on a
comprehensive clinical evaluation. Additional testing
with polysomnography and time-synchronized video
recording may be indicated for cases that are associated
with very frequent episodes, complaints of excessive
sleepiness, unusual presentation, or injury to the
individual or bed partner. Polysomnography is also
indicated if an underlying seizure activity is suspected,
in which case additional electroencephalographic
leads are needed. Multiple polysomnographic studies
performed over several nights may be required. Extensive
neurological and psychiatric assessment may be considered
for cases with medico-legal implications. Therapy of all
parasomnias should include education regarding patient
and bed partner safety as well as the avoidance of known
precipitating factors. Unlike the relatively benign course
of the arousal disorders, RBD may be a harbinger of
significant neurologic disease and these patients should
undergo regular clinical surveillance for the subsequent
emergence of neurodegenerative diseases.
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Reprint requests: Dr Greg Matwiyoff, Sleep Medicine Center, National Jewish Health, 1400 Jackson Street, Denver, CO 80206, USA
e-mail: [email protected]