5 - SLEEP DISORDERS
Parasomnias are undesirable
behavioral, autonomic nervous system, or experiential phenomena
during sleep, usually characterized by increased motor and/or
autonomic activity, sleep-wake state dissociation, altered responsiveness
to the environment, and retrograde amnesia. Specific parasomnias
arise during sleep-wake transitions, NREM sleep, or REM sleep
and are often divided into two groups. Primary parasomnias are
disorders of sleep states per se, and secondary parasomnias
are disorders of other organ systems that arise during sleep.
Virtually all primary parasomnias represent an admixture or
simultaneous occurrence of elements of both wakefulness and
The most common primary
parasomnias are disorders of arousal and REM sleep disorders.
Disorders of arousal include confusional arousals, sleepwalking,
and sleep terrors, all characterized by partial arousals from
NREM sleep. REM sleep parasomnias include nightmares, characterized
by frightening dreams and autonomic arousal, and REM behavior
disorder (RBD), characterized by absence of the muscle atonia
normally present during REM sleep. The behaviors associated
with primary parasomnias may lead to injury of the patient or
bed partner, and may have forensic implications.
parasomnias, such as sleep-related expiratory groaning, or esophageal
spasm, have been reported. Typically, descriptions have been
provided for single cases or very small case series, making
scientific evaluation difficult. These phenomena are likely
to be quite common, but are often unrecognized, misdiagnosed,
or ignored in clinical practice. The pathophysiology, morbidity,
and functional consequences of secondary parasomnias are unknown.
In The Last 5 Years
studies have shown that disorders of arousal occur in about
10% of adults, and are usually not associated with significant
underlying psychiatric or psychological disorders. These disorders
are very common in children, but may begin during adulthood
or persist into adulthood or. There is growing evidence for
genetic determinants of these disorders of arousal.
- Exogenous triggers
have been identified for disorders of arousal in predisposed
individuals. These include sleep deprivation, alcohol ingestion,
- The basic sleep
architecture and sleep macrostructure is normal in patients
with disorders of arousal. "Hypersynchronous delta"
activity has not been substantiated as an EEG marker for disorders
of arousal. However, quantitative EEG analyses in patients with
disorders of arousal indicate instability of slow wave sleep,
particularly during the first slow-wave sleep period of the
night. This instability may be related to cyclic alternating
- RBD, which may
have a prevalence as high as 0.5%, has two striking demographic
features: 90% of affected individuals are male, and most cases
begin after 50 years of age. Clonazepam is efficacious in 90%
- At least 50% of
RBD cases are related to recognized neurologic conditions, particularly
narcolepsy and the synucleinopathies (Parkinson's disease, multiple
system atrophy, and dementia with Lewy bodies). RBD may precede
the appearance of other features of the underlying disease by
as many as 10 years. RBD may also be iatrogenic, due primarily
to medications such as selective serotonin reuptake inhibitors
- Functional neuroimaging
studies have documented reduced dopamine transporters and decreased
dopaminergic innervation of the basal ganglia in patients with
- Other conditions
characterized by sleep-wake state dissociations have been identified,
and may be related to RBD. These include parasomnia overlap
syndrome, agrypnia excitata, and status dissociatus.
- Better define the
pathophysiology and neuroanatomic substrates of primary parasomnias
in human and animal studies. In humans, specific methods could
include functional neuroimaging and quantitative EEG studies
(e.g., investigations of cyclic alternating pattern in disorders
of arousal). Psychophysiological and neurophysiological studies
could help to identify factors that trigger and maintain chronic
parasomnias. A brain bank for RBD and other parasomnias would
be particularly useful to study their structural and genetic
origins. The identification of genetic and environmental factors
involved in the etiology and pathogenesis of primary parasomnias
may be facilitated by the presence of distinctive phenotypes
for these disorders. Animal models for parasomnias could involve
techniques such as genetic manipulations, brain lesions and
brain stimulation, sleep deprivation and other behavioral provocation
techniques, and pharmacologic manipulations. In particular,
animal studies investigating motor control and sleep could help
to further elucidate the pathophysiology of parasomnias.
- Investigate pharmacologic
and behavioral treatments for primary and secondary parasomnias
in clinical trials. Intervention studies could help to identify
both common and distinctive mechanisms of action for different
treatments in different disorders.
- Further define
the relationships between the different parasomnias, and between
parasomnias and other neurological disorders. For instance,
the relationship between disorders of arousal and nocturnal
seizures, particularly nocturnal frontal lobe epilepsy, should
be further investigated. Relationships between RBD, neuropsychiatric
disorders, and specific medications need to be better defined.
- Obtain clinical
and physiological information regarding secondary parasomnias
as a first step toward identifying the prevalence, etiology,
and efficacious treatment of these disorders.
are among the most common clinical sleep disturbances experienced
in childhood, little is known about the underlying neurophysiologic
mechanisms and neurotransmitter systems responsible for their
development and relative importance.
Although there is
a genetic predisposition for many parasomnias, the specific
genes involved have yet to be identified, and little is known
about the interaction between genetic phenotype, other aspects
of sleep physiology such as arousal threshold, and sleep inertia
and environmental factors. Treatment strategies involving pharmacologic
and behavioral interventions have been developed, but most outcome
studies have included very small sample sizes and short-term
In The Last 5 Years
- Several studies
have reported an association between partial arousal parasomnias
and both migraine headaches and Tourette's syndrome in children,
raising the possibility that serotonergic pathways may be involved.
Case reports of novel treatment strategies for partial arousal
parasomnias have suggested that behavioral interventions such
as scheduled awakenings and hypnotherapy may be effective non-pharmacologic
treatment options, but little is known about the underlying
mechanism responsible for the clinical response.
- Examine interactions
between the developing central nervous system, genetics, other
aspects of sleep physiology, and environmental factors in determining
phenotypic expression of partial arousal parasomnias in childhood.
- Examine the role
of various neurotransmitter systems in the neurophysiology of
partial arousal parasomnias.
- Evaluate the efficacy
of, and underlying mechanisms for, pharmacologic and non-pharmacologic
treatment strategies for partial arousal parasomnias and rhythmic
movement disorders in childhood.