Literary allusions referencing the phenomenology of sleep are evident throughout history, as evident in Virgil's (70 B.C. - 19 B. C.) Aeneid, 'That sweet, deep sleep, so close to tranquil death'. This perennial fascination with sleep has even engendered appraisal in mythology. In ancient Greece, sleep was personified by the deity Hypnos, while his Roman equivalent was named Somnos. Even now, the precise impetus of the phenomenology of sleep remains elusive, leading to a somewhat residual arcane enchantment with sleep.
Sleep disturbances are one of the most abundant presentations in the outpatient setting. In fact, up to 50% of chief complaints in the primary care setting correlate with maladaptive sleep patterns. Normal sleep architecture is composed of rapid eye movement (REM) and non-REM (NREM). NREM is further subdivided into four stages, stage 0, stage 1, stage 2, and stage 3. NREM and REM alternate in a cycle that lasts about 120 minutes. The initial REM stage lasts about 5-10 minutes, followed by progressively protracted and frequent periods.
Disruptions to this sleep cycle, either during continuous sleep or upon the transition to wakefulness, are categorized under the nosology of 'parasomnias'. The nomenclature of 'parasomnias' was first introduced by Henri Roger in 1932. The etymology derives from the prefix para (Greek) - 'alongside' - and the noun Somnus (Latin) - 'sleep'. Parasomnias are characterized by aberrant behavioral, phenomenological, or physiological events in accordance with sleep. The most prevalent deviant patterns of sleep arousal, and the ones of salience for this scholastic endeavor, consist of 'REM sleep behavior disorder,' 'NREM sleep arousal disorders,' and 'nightmare disorder'.
The etiology of parasomnias remains postulations, as no specific origin has been clearly delineated; however, a plethora of theories have surfaced. Regarding NREM sleep disturbances, recent evidence suggests that disruptions of stage 3 slow-wave sleep can increase one's diathesis. Such conditions that can fragment slow-wave sleep include genetic susceptibility, restless leg syndrome, sleep deprivation, periodic limb movements, noise, sleep-related breathing disorders, touch, alcohol, stress, medications, and fever.  Although still unproven, some experts suggest a link between REM sleep disorders and neurodegenerative diseases with diminished dopamine activity in the striatum, as well as a posttraumatic stress disorder, and narcolepsy.
NREM sleep disorders are more common in the younger demographic, whereas REM sleep disturbances more often present later in life. Sleepwalking is more common in children than in adults. Experts estimate that roughly 15% of children will experience at least one sleepwalking episode; however, by adolescence, most will outgrow this disorder, diminishing the prevalence to just 2 to 4%. One study revealed that 47% of children with one parent with a history of sleepwalking experienced sleepwalking; the prevalence increased to 61.5% for children with two sleepwalking parents.
Sleep terrors are much less common in the pediatric population, with estimations as low as 3%. Nightmare disorder affects up to 6% of the population. REM sleep behavior disorder only appears in 1% of the general population, but at least 50% of those with REM sleep disorder suffer from comorbid neurodegenerative disorders, such as Parkinson disease, dementia with Lewy bodies, and multiple system atrophy.
Non-rapid Eye Movement (NREM) Sleep Arousal Disorders
Non-rapid eye movement (NREM) sleep arousal disorders comprise of sleepwalking and sleep terrors. These peculiarities represent aspects of both wakefulness and NREM sleep, manifesting as complex motor patterns without conscious awareness, also called 'state dissociation.' Sleepwalking typically occurs during the first third of the sleep cycle, during stage 2 and stage 3, within three hours of falling asleep. Individuals will experience repeated episodes of walking, often purposelessly, after falling asleep. In this trance-like state, individuals maintain a blank stare and are unresponsive to external stimuli. When finally awakened, orientation returns within minutes; however, recall is minimal. The episodes are ephemeral, typically lasting less than ten minutes. However, there is cause for concern as the sleepwalker's ability to open doors and windows remains intact.
Sleep terrors, more commonly referred to as night terrors, also occur during the first third of the sleep cycle. The phenomenology of sleep terrors transpires as abrupt partial arousal from delta wave sleep. Sleep terrors are associated with frantic motor activity and screaming. This hyperactivity is followed by a period of intense anxiety and hyperarousal. NREM sleep arousal disorders are associated with amnesia, confusion, and disorientation.
As its name implies, nightmare disorder is a distressing pattern of repeated, dysphoric, and vivid dreams. Themes of the nightmares tend to consist of threats to survival, physical well being, and security. Unlike the previously mentioned NREM sleep disorders, nightmares occur during the second half of the sleep cycle, with recollection intact, upon awakening. Because nightmares often transpire during REM, movement and vocalizations do not occur. Evaluations of well-being may be inversely related to the manifestation of nightmares.
Rapid Eye movement Sleep Behavior Disorder
Normal physiologic sleep function involves atonia during REM. This atonic phenomenon is conducive to self-preservation as humans tend to have their most vivid dreams during REM. If the tonic state were similarly active during REM as when awake, then one could, presumably, physically act out his or her dream, which in turn is what transpires in REM sleep behavior disorder.
REM sleep behavior disorder characteristically presents with repeated episodes of vocalization and/or abnormal motor patterns during REM. Because REM occurs most frequently in the latter half of the night, so too follows this behavioral anomaly. This disorder has, appropriately, been identified as 'dream enacting behavior,' as it reflects the dream content. The behavior is often disconcerting for both the individual, as he or she commonly suffers injury in the reenactment of the dream, and for the bed partner, as the vocalizations are frequently vociferous and profane. Similar to nightmare disorder, upon awakening, patients with REM sleep behavior disorder will maintain recall of the events of the preceding evening.
Patients presenting with sleep-associated disturbances should undergo a thorough assessment of their sleep history, as well as medical and psychiatric history. Ideally, a 'sleep history outline' will be obtained, which analyzes the patient's banal sleep patterns. The medical history should include prescribed and recreational drug use. Medications that reportedly induce or exacerbate parasomnias include selective serotonin reuptake inhibitors, tricyclic antidepressants, venlafaxine, monoamine oxidase inhibitors, beta-adrenergic blocking agents, zolpidem, and zopiclone.
Furthermore, patients are encouraged to initiate a sleep log to document their sleep patterns. When possible, the patient's bed partner should be interviewed, as well, to investigate the incidence of breathing difficulties, leg jerks, and snoring. The gold standard diagnostic tool in sleep medicine is polysomnography. This procedure implements the trifecta of electroencephalography (EEG), electromyography (EMG), and electrooculographic (EOG) tracings during sleep. Polysomnography provides objective means to assess sleep continuity, REM physiology, sleep architecture, oxygen restoration, cardiac arrhythmias, sleep-related breathing impairment, and periodic movements. A somnologist should see patients with complicated sleep behavior.
The DSM-V identifies specific criteria to distinguish individual sleep-wake disorders. NREM sleep disorders, which include sleepwalking and sleep terrors, normally occur during the first third of the sleep episode. The events tend to be amnestic in nature as little to no dream content is recalled. These episodes cause significant distress, and lastly, are not attributable side effects of an exogenous substance. Nightmare disorder is identified by the presence of extremely dysphoric well-remembered dreams that are often thematic related to threats to survival; persons suffering from nightmare disorder awake and rapidly become oriented and alert. The taxon 'nightmare disorder' is assigned when the intensity of the nightmares and subsequent distress indicates the need for clinical attention.
REM sleep disorders consist of episodes of arousal during REM sleep; this has been described as if the patient were acting out his or her dream, which can ultimately be dangerous for both the patient and their bed partner. These typically occur more than 90 minutes after sleep onset. Individuals are completely awake, alert, and oriented upon awakening from an episode. EEG and EMG will identify REM sleep patterns without atonia.
Although polysomnography can be useful to investigate most parasomnias, only REM sleep behavior disorder is readily distinguishable through this procedure. Readings will reveal sustained EMG activity in REM sleep.
Most parasomnias can be treated, in some capacity, with benzodiazepines (BZD). There have been suggestions that the therapeutic value of BZDs arises from their ability to suppress stages of deep sleep and REM, which are the stages implicated in parasomnias.
However, because of their undesirable side effect profile and addiction potential, alternatives are commonly suggested; such alternatives include tricyclic antidepressants, melatonin, and selective serotonin reuptake inhibitors (SSRIs). Alpha-1 antagonists, such as prazosin, have demonstrated specific efficacy in the treatment of nightmare disorders. Non-pharmacological treatment modalities encompass psychotherapy, scheduled awakenings, hypnosis, and relaxation exercises.
Another therapeutic approach specific to nightmare disorder is 'imagery rehearsal.' This psychotherapeutic approach consists of identifying a recurrent nightmare and changing the storyline to a more agreeable thematic sequence. As the patient rehearses this novel storyline, he or she will inadvertently change subsequent dream imagery.
The provider should evaluate the patient for underlying comorbidities, as parasomnias can commonly present as sequelae; i.e., the onset of first-episode sleepwalking in adults should prompt the investigation of nocturnal seizures, breathing-related sleep disorder, and medication profiles.
Traits of variant parasomnias can overlap with one another, thus producing some difficulty in the demarcation between disorders. However, some features of salience can help the clinician delineate parasomnias. For instance, generally, during NREM sleep disorders, the patient's eyes remain open, whereas, in REM sleep disorders, they remain closed. Sleep terrors are often associated with anxiety, depression, obsessive-compulsive, and phobic disorders, whereas nightmares have correlated with delirium, febrile illness, withdrawal from drugs and alcohol, and chronic illness.
Fortunately, most parasomnias appear to either resolve by adolescence or precipitate as isolated phenomena. If parasomnias are the manifestations of underlying comorbid conditions, as the inciting condition is treated, so too will the parasomnias diminish. Of note, upon the discontinuation of benzodiazepines, it is conceivable that a patient may experience relapse, or in times of stress.
Complications arise if a patient injures himself or his bed partner during a parasomniac episode.
Proper sleep hygiene may prove as the best intervention to halt subsequent NREM and REM sleep behavior disorders. Furthermore, by implementing precautions such as installing alarms on doors, having a patient sleep on the first floor, and placing latches on windows, the patient can sleep the assurance that they will have protection from injury. The bed partner should also be educated regarding possible violent behavioral patterns to obviate impending harm.
As noted previously, parasomnias can be distressing events for both the patient and bed partner. Fortunately, most disturbances resolve spontaneously by adolescence. For the residual and late-onset parasomnias, proper identification and management are vital. Efficient healthcare intervention includes appropriate referrals to specialists and clinics. Because parasomnias can arise as secondary manifestations of underlying conditions, differentials must be ruled out. Again, this is best accomplished by pharmacy consultations and referrals to the appropriate specialists.
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