HYPERSOMNIAS OF CENTRAL ORIGIN NOT DUE TO A CIRCADIAN RHYTHM SLEEP DISORDER, SLEEP RELATED BREATHING DISORDER, OR OTHER CAUSE OF DISTURBED NOCTURNAL SLEEP

NARCOLEPSY WITH CATAPLEXY

Narcolepsy with cataplexy is primarily characterized by excessive daytime sleepiness and cataplexy. Many of the symptoms of narcolepsy with cataplexy are due to an unusual proclivity to transition rapidly from wakefulness into rapid eye movement (REM) sleep and to experience dissociated REM sleep events.

Excessive daytime sleepiness is usually the most disabling symptom and the first to occur. It is characterized by repeated episodes of naps or lapses into sleep across the daytime. Patients with narcolepsy with cataplexy typically sleep for a short duration and awaken refreshed but within two or three hours begin to feel sleepy again. The pattern repeats itself through the day. Sleepiness is more likely to occur in boring monotonous situations that require no active participation, for example, watching television. Sudden and often irresistible sleep attacks (that is, a sudden onset of sleep or involuntary sleep episodes) may also occur in unusual situations such as eating, walking, or driving. Sleep attacks usually occur within a background of overall sleepiness. Sleepiness in narcolepsy with cataplexy varies in severity and is not easily distinguishable from the sleepiness caused by insufficient sleep or other sleep disorders.

In cases in which sleepiness is severe, a symptom called ¡§automatic behavior¡¨ is occasionally observed: the patient continues an activity in a semiautomatic fashion without memory or consciousness. A patient may, for example, continue to write sentences in a letter or work on the computer, but the output will be nonsensical.

Cataplexy, a unique characteristic of narcolepsy, is characterized by sudden loss of bilateral muscle tone provoked by strong emotions that are usually positive, such as laughter, pride, elation, or surprise. Negative emotions such as anger may also occasionally be a trigger. Cataplexy can be localized, or it can include all skeletal muscle groups. The lower or upper limbs, neck, mouth, or eyelids may be regionally affected. Affected areas most commonly include the knees, face, and neck. Blurred vision may occur and may reflect oculomotor involvement. Respiratory muscles are never affected, but a feeling of choking may result from the occurrence of cataplexy in an awkward position. The duration of cataplexy is usually short, ranging from a few seconds to several minutes at most, and recovery is immediate and complete.

Cataplexy may vary in pattern, frequency, and severity. The loss of muscle tone ranges from a mild sensation of weakness¡Xwith head drop, facial sagging, jaw weakness, slurred speech, and buckling of the knees¡Xto complete postural collapse. Twitches and jerks may occur, particularly in the face, as the patient is trying to fight the episode. In severe episodes, it usually takes several seconds before a complete state of muscle weakness is reached, preventing serious injuries in most instances. When mild, the weakness may not be very noticeable; for example, a simple drooping of the eye or the corner of the mouth may occur. Cataplexy may sometimes be followed by sleep. The frequency of cataplexy shows wide interpersonal variation from rare events during a year-long period in some patients to countless attacks in a single day in others. Patients may learn to avoid situations that induce cataplexy and may have a decrease in the frequency of cataplectic events over time.

In very rare cases, strong emotion may provoke episodes of cataplexy in succession. This is termed status cataplecticus. Episodes of status can last for many minutes, even up to an hour. The use of adrenergic or serotoninergic antidepressant medications (including tricyclic antidepressants) promptly ameliorates cataplexy in the great majority of cases. Episodes of status cataplecticus are most often observed when these medications are withdrawn, resulting in a rebound cataplexy.

NARCOLEPSY WITHOUT CATAPLEXY

Excessive daytime sleepiness in narcolepsy without cataplexy is most typically associated with naps that are refreshing in nature while nocturnal sleep is normal or moderately disturbed without excessive amounts of sleep. Sleep paralysis, hypnagogic hallucinations, or automatic behavior may be present. In a meta-analysis, the mean sleep latency on the MSLT in patients with narcolepsy without cataplexy was 3.1 „b 2.9 minutes. An essential feature of the diagnosis is the presence of a mean sleep latency less than or equal to eight minutes and two or more SOREMPs on an MSLT.

NARCOLEPSY DUE TO MEDICAL CONDITION

The direct cause of narcolepsy due to medical condition is a coexisting medical or neurological disorder. Narcolepsy must be documented either clinically (with definite cataplexy, as defined in the narcolepsy with cataplexy section) or polysomnographically (without clear cataplexy but with a short mean sleep latency and two SOREMPs on the MSLT).

Daytime sleepiness in these cases may be of variable severity. Sleep paralysis, hypnagogic hallucination, insomnia, or automatic behavior may or may not be present.

Disorders that have been shown to produce genuine secondary narcolepsy with cataplexy include tumors or sarcoidosis of the hypothalamus, multiple sclerosis plaques impairing the hypothalamus, paraneoplastic syndrome with anti-Ma2 antibodies, Neiman-Pick type C disease, and possibly Coffin-Lowry Syndrome. Several other neurological disorders have been associated with narcolepsy, generally without cataplexy, including head trauma, multiple sclerosis, myotonic dystrophy, Prader-Willi syndrome, Parkinson¡¦s disease, and multiple system atrophy. In complex cases, for example, after head trauma, clinical judgment should be used to determine if the development of narcolepsy was a mere coincidence or was triggered by the event.

In disorders associated with both SRBDs and central nervous system hypersomnia with SOREMPs on the MSLT (for example, myotonic dystrophy or Prader-Willi syndrome), this diagnostic category should be used only if SOREMPs on the MSLT persist after the SRBD is adequately treated.

RECURRENT HYPERSOMNIA (Including Klein-Levin Syndrome and Menstrual-Related Hypersomnia)

The best-characterized recurrent hypersomnia is Klein-Levin syndrome, and this section primarily pertains to this condition. Other less well-characterized recurrent hypersomnias are described as clinical subtypes. Recurrent hypersomnia is characterized by recurrent episodes of hypersomnia often associated with other symptoms that typically occur weeks or months apart.

Episodes usually last a few days to several weeks and appear once to 10 times a year. Episodes are often preceded by prodromes such as fatigue or headache lasting a few hours. Patients may sleep as long as 16 hours to 18 hours per day, waking or getting up only to eat and void. Urinary incontinence does not occur. Body weight gain of a few kilograms is often observed during the episode. Cognitive abnormalities such as feelings of unreality, confusion, and hallucinations may occur. Behavioral abnormalities such as binge eating, hypersexuality, irritability, and aggressiveness may be present. Patients may respond verbally, but often unclearly or aggressively, when aroused by strong stimuli during the episode. The simultaneous occurrence of all these symptoms is the exception rather than the rule, and in some cases, isolated recurrent hypersomnia may be the only symptom. Amnesia, transient dysphoria, or elation with insomnia may signal the termination of an episode. To be characterized as recurrent hypersomnia, sleep and general behavior must be normal between episodes.

IDIOPATHIC HYPERSOMNIA WITH LONG SLEEP TIME

Idiopathic hypersomnia with long sleep time is characterized by constant and severe excessive sleepiness with prolonged but unrefreshing naps of up to three or four hours, a prolonged major sleep episode, and great difficulty waking up either in the morning or at the end of a nap. The major sleep episode is prolonged to at least 10 hours (typically 12 to 14 hours) with few or no awakenings. Post-awakening confusion (sleep drunkenness) is often reported. In a research setting, idiopathic hypersomnia with long sleep time is typically diagnosed only in the presence of long sleep time and is a unique disease entity. More recently, the term idiopathic hypersomnia has been used to include subjects with hypersomnolence without increased nocturnal sleep. In the current diagnostic classification, these two variants have been separated.

IDIOPATHIC HYPERSOMNIA WITHOUT LONG SLEEP TIME

The major clinical feature of idiopathic hypersomnia without long sleep time is a complaint of constant and severe excessive daytime sleepiness. Daytime sleepiness results in unintended naps that are generally of nonrefreshing nature. Cataplexy is absent. The major sleep episode (e.g., nighttime) is either normal or slightly prolonged (less than 10 hours), usually with few or no awakenings. Patients sometimes have great difficulties waking up in the morning and from naps. Post-awakening confusion (sleep drunkenness) is often reported.

BEHAVIORALLY INDUCED INSUFFICIENT SLEEP SYNDROME

Behaviorally induced insufficient sleep syndrome occurs when an individual persistently fails to obtain the amount of sleep required to maintain normal levels of alertness and wakefulness. The individual engages in voluntary, albeit unintentional, chronic sleep deprivation. Examination reveals unimpaired or above-average ability to initiate and maintain sleep, with little or no psychopathology. Physical examination reveals no medical explanation for the patient¡¦s sleepiness. A detailed history of the current sleep pattern reveals a substantial disparity between the need for sleep and the amount actually obtained. Its significance is unappreciated by the patient. A markedly extended sleep time on weekend nights or during holidays as compared to weekday nights is also suggestive of this disorder. A therapeutic trial of a longer major sleep episode can reverse the symptoms. Additional symptoms such as sleep paralysis and hypnagogic hallucination may occur.

HYPERSOMNIA DUE TO MEDICAL CONDITION

The direct cause of hypersomnia due to medical condition is a coexisting medical or neurological disorder that produces hypersomnia. Cataplexy must not be present. If a MSLT is performed, the results obtained must not qualify for a diagnosis of narcolepsy without cataplexy (namely, a mean sleep latency less than eight minutes and two or more SOREMPs). Daytime sleepiness may be of variable severity and may resemble that of either narcolepsy (i.e., refreshing effects of naps) or idiopathic hypersomnia with long sleep time (i.e., a long sleep episode and unrefreshing sleep). Sleep paralysis, hypnagogic hallucinations, or automatic behavior may or may not be present. In the case of disorders associated with both SRBDs and hypersomnia due to medical condition, a diagnosis of hypersomnia due to medical condition should be made only if the hypersomnia persists after adequate treatment of the SRBDs. Hypersomnia secondary to psychiatric disorders, drugs of abuse, or the effects of prescribed medications are classified elsewhere. Hypersomnia due to medical condition is only diagnosed if the medical condition is judged to be directly causing the hypersomnia. Hypersomnia has been described in association with a large range of conditions, including head trauma, stroke, encephalitis, inflammatory conditions, tumors, and genetic and neurodegenerative diseases.

HYPERSOMNIA DUE TO DRUG OR SUBSTANCE

This diagnostic category should be reserved for patients with excessive nocturnal sleep, daytime sleepiness, or excessive napping that is believed to be secondary to substance use. Hypersomnia due to drug or substance covers hypersomnias associated with tolerance to or withdrawal from various prescribed or street drugs, and alcohol. If narcolepsy or hypersomnia existed prior to stimulant abuse, the category should not be used.

HYPERSOMNIA NOT DUE TO SUBSTANCE OR KNOWN PHYSIOLOGICAL CONDITION (Nonorganic Hypersomnia, NOS)

In hypersomnia not due to substance or known physiological condition, excessive nocturnal sleep, daytime sleepiness, or excessive napping are reported; sleep is perceived as nonrestorative and generally of poor quality. Patients are often intensely focused on their hypersomnia, and psychiatric symptoms typically become apparent only after prolonged interviews or psychometric testing. Causative psychiatric conditions include mood disorders, conversion or undifferentiated somatoform disorder, and less frequently other mental disorders such as schizoaffective disorder, adjustment disorder, or personality disorders.

PHYSIOLOGICAL (ORGANIC) HYPERSOMNIA, UNSPECIFIED (Organic Hypersomnia, NOS)

Disorders that satisfy clinical (a complaint of excessive sleepiness occurring almost daily for at least three months) and MSLT (mean sleep latency less than eight minutes with fewer than two SOREMs) criteria for hypersomnolence and are believed to be due to a physiological condition, but do not meet criteria for other hypersomnolence conditions, are classified here.

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Source: American Academy of Sleep Medicine, International Classification of Sleep Disorders, 2nd ed.: Diagnostic and Coding Manual, Westchester, Illinois: American Academy of Sleep Medicine, 2005.