DSM-IV

Diagnostic Criteria

A. Irresistible attacks of refreshing sleep that occur daily over at least 3 months.

B. The presence of one or both of the following:

  1. cataplexy (i.e., brief episodes of sudden bilateral loss of muscle tone, most often in association with intense emotion)
  2. recurrent intrusions of elements of rapid eye movement (REM) sleep into the transition between sleep and wakefulness, as manifested by either hypnopompic or hypnagogic hallucinations or sleep paralysis at the beginning or end of sleep episodes

C. The disturbance is not due to the direct physiological effects of a substance (e.g., a drug of abuse, a medication) or another general medical condition.

Differential Diagnosis

Narcolepsy must be differentiated from normal variations in sleep, sleep deprivation, other primary Sleep Disorders, and Sleep Disorder Related to Another Mental Disorder, Hypersomnia Type. Many individuals feel some sleepiness during the day, particularly in the afternoon hours when an increase in physiological sleepiness occurs. However, such individuals do not have irresistible sleep at other times of the day and can "fight through" their sleepiness with increased mental and physical effort. They generally do not experience cataplexy, sleep-related hallucinations, or sleep paralysis.

Sleep deprivation

Sleep deprivation from any cause produces daytime sleepiness. Narcolepsy should be diagnosed only if the individual has demonstrated a regular sleep-wake schedule with an adequate amount of nocturnal sleep. Sleep deprivation and irregular sleep schedules may rarely lead to sleep-related hallucinations or sleep paralysis, but not to cataplexy.

Primary Hypersomnia

The degree of daytime sleepiness may be similar in individuals with Narcolepsy and Primary Hypersomnia. Compared with individuals with Narcolepsy, individual with Primary Hypersomnia generally describe prolonged and less disrupted nocturnal sleep. Daytime sleepiness in Primary Hypersomnia consists of more prolonged, unrefreshing sleep periods, which have less urgency than the sleep "attacks" of Narcolepsy and are less often associated with dreaming. Individuals with Primary Hypersomnia do not manifest cataplexy, sleep-related hallucinations, or sleep paralysis. Nocturnal polysomnography confirms less disrupted sleep and normal REM latency in individuals with Primary Hypersomnia, and the MSLT does not show sleep-onset REM periods.

Breathing-Related Sleep Disorder

Individuals with Breathing-Related Sleep Disorder often experience excessive sleepiness that is equal in magnitude to that of individuals with Narcolepsy. Furthermore, many individuals with Narcolepsy may develop some degree of sleep apnea. Breathing-Related Sleep Disorder is distinguished from Narcolepsy by a history of loud snoring; breathing pauses that disrupt nocturnal sleep; lengthy, unrefreshing daytime sleep episodes; and the absence of accessory symptoms such as cataplexy. Polysomnography can identify breathing pauses (apneas) in individuals with Breathing-Related Sleep Disorder. Apneas in individuals with Narcolepsy tend to be less frequent and associated with less oxyhemoglobin desaturation. If an individual presents an unambiguous history of Narcolepsy together with confirmatory polysomnographic findings (sleep-onset REM) and also has evidence of Breathing-Related Sleep Disorder during polysomnography, both diagnoses can be made. If an individual has sleep-onset REM and sleep apnea activity during polysomnography, but does not have the full clinical syndrome of Narcolepsy, then only a diagnosis of Breathing-Related Sleep Disorder should be made.

Hypersomnia Related to Another Mental Disorder

Individuals with Hypersomnia Related to Another Mental Disorder may report excessive sleepiness and intense dreams. In particular, Major Depressive Episodes With Atypical Features and Bipolar Disorder, Most Recent Episode Depressed, often involve an intense need for sleep during the daytime. However, individuals with Mood Disorders typically have prolonged nocturnal sleep in contrast to the short, fragmented sleep of Narcolepsy. Daytime naps are not refreshing in individuals with Mood Disorders. Furthermore, these individuals do not have the accessory symptoms that are characteristic of Narcolepsy (e.g., cataplexy), although individuals who have Major Depressive Disorder, With Psychotic Features, may complain of hallucinations near sleep and at other times. Polysomnographic studies of individuals with Mood Disorders may reveal short REM latency, but typically not as short as that seen in Narcolepsy. Nocturnal sleep latency is also longer in individuals with Mood Disorders. Finally, daytime testing with the MSLT shows a much lower degree of physiological sleepiness and infrequent sleep-onset REM periods in individuals with Mood Disorders. Thus, the "sleepiness" in these individuals appears to be more a manifestation of psychomotor retardation and anergy.

Substance-Related Disorders

The use of, or withdrawal from, substances (including medications) may produce some symptoms of Narcolepsy. Cholinergic agonists (including anticholinesterase pesticides) can disrupt sleep continuity and enhance REM sleep. Similar effects can result from the abrupt discontinuation of anticholinergic agents, including tricyclic antidepressants. Reserpine and methyldopa can enhance REM sleep and produce sleepiness. Withdrawal from stimulants can produce severe somnolence. A diagnosis of Substance-Induced Sleep Disorder, Hypersomnia Type, might be warranted if the symptoms are judged to be due to the direct physiological effects of a substance. Conversely, a diagnosis of Narcolepsy should not be made if the individual is taking or has recently discontinued taking such substances.

Sleep Disorder Due to a General Medical Condition

Narcolepsy must be distinguished from Sleep Disorder Due to a General Medical Condition, Hypersomnia Type. The diagnosis is Sleep Disorder Due to a General Medical Condition when the symptom are judged to be the direct physiological consequence of a specific general medical condition (e.g., closed head injury or hypothalamic tumor).

DSM-5

Diagnostic Criteria

A. Recurrent periods of an irrepressible need to sleep, lapsing into sleep, or napping occurring within the same day. These must have been occurring at least three time per week over the past 3 months.

B. The presence of at least one of the following:

  1. Episodes of cataplexy, defined as either (a) or (b), occurring at least a few times per month:
    • a. In individuals with long-standing disease, brief (seconds to minutes) episodes of sudden bilateral loss of muscle tone with maintained consciousness that are precipitated by laughter or joking.
    • b. In children or in individuals within 6 months of onset, spontaneous grimaces or jaw-opening episodes with tongue thrusting or a global hypotonia, without any obvious emotional triggers.
  2. Hypocretin deficiency, as measured using cerebrospinal fluid (CSF) hypocretin-1 immunoreactivity values (less than or equal to one-third of values obtained in healthy subjects tested using the same assay, or less than or equal to 110 pg/mL). Low CSF levels of hypocretin-1 must not be observed in the context of acute brain injury, inflammation, or infection.
  3. Nocturnal sleep polysomnography showing rapid eye movement (REM) sleep latency less than or equal to 15 minutes, or a multiple sleep latency test showing a mean sleep latency less than or equal to 8 minutes and two or more sleep-onset REM periods.

Specify whether:

  • Narcolepsy without cataplexy but with hypocretin deficiency: Criterion B requirements of low CSF hypocretin-1 levels and positive polysomnography/multiple sleep latency test are met, but no cataplexy is present (Criterion B1 not met).
  • Narcolepsy with cataplexy but without hypocretin deficiency: In this rare subtype (less than 5% of narcolepsy cases), Criterion B requirements of cataplexy and positive polysomnography/multiple sleep latency test are met, but CSF hypocretin-1 levels are normal (Criterion B2 not met).
  • Autosomal dominant cerebellar ataxia, deafness, and narcolepsy: This subtype is caused by exon 21 DNA (cytosine-5)-methyltransferase-1 mutations and is characterized by late-onset (age 30-40 years) narcolepsy (with low or intermediate CSF hypocretin-1 levels), deafness, cerebellar ataxia, and eventually dementia.
  • Autosomal dominant narcolepsy, obesity, and type 2 diabetes: Narcolepsy, obesity, and type 2 diabetes and low CSF hypocretin-1 levels have been described in rare cases and are associated with a mutation in the myelin oligodendrocyte glycoprotein gene.
  • Narcolepsy secondary to another medical condition: This subtype is for narcolepsy that develops secondary to medical conditions that cause infectious (e.g., Whipple's disease, sarcoidosis), traumatic, or tumoral destruction of hypocretin neurons. Note: Record first the underlying medical condition (e.g., Whipple's disease; narcolepsy secondary to Whipple's disease).

Specify current severity:

  • Mild: Infrequent cataplexy (less than once per week), need for naps only once or twice per day, and less disturbed nocturnal sleep.
  • Moderate: Cataplexy once daily or every few days, disturbed nocturnal sleep, and need for multiple naps daily.
  • Severe: Drug-resistent cataplexy with multiple attacks daily, nearly constant sleepiness, and disturbed nocturnal sleep (i.e., movements, insomnia, and vivid dreaming).

Subtypes

In narcolepsy without cataplexy but with hypocretin deficiency, unclear "cataplexy-like" symptoms may be reported (e.g., the symptoms are not triggered by emotions and are unusually long lasting). In extremely rare cases, cerebrospinal fluid (CSF) levels of hypocretin-1 are low, and polysomnographic/multiple sleep latency test (MSLT) results are negative: repeating the test is advised before establishing the subtype diagnosis. In narcolepsy with cataplexy but without hypocretin deficiency, test results for human leukocyte antigen (HLA) DQB1*06:02 may be negative. Seizures, falls of other origin, and conversion disorder (functional neurological symptoms disorder) should be excluded. In narcolepsy secondary to infectious (e.g., Whipple's disease, sarcoidosis), traumatic, or tumoral destruction of hypocretin neurons, test results for HLA DQB1*06:02 may be positive and may result from the insult triggering the autoimmune process. In other cases, the destruction of hypocretin neurons may be secondary to trauma or hypothalamic surgery. Head trauma or infections of the central nervous system can, however, produce transitory decreases in CSF hypocretin-1 levels without hypocretin cell loss, complicating the diagnosis.

Differential Diagnosis

Other hypersomnias

Hypersomnolence and narcolepsy are similar with respect to the degree of daytime sleepiness, age of onset, and stable course over time but can be distinguished based on distinctive clinical and laboratory features. Individuals with hypersomnolence typically have longer and less disrupted nocturnal sleep, greater difficulty awakening, more persistent daytime sleepiness (as opposed to more discrete "sleep attacks" in narcolepsy), longer and less refreshing daytime sleep episodes, and little or no dreaming during daytime naps. By contrast, individuals with narcolepsy have cataplexy and recurrent intrusions of elements of REM sleep into the transition between sleep and wakefulness (e.g., sleep-related hallucinations and sleep paralysis). The MSLT typically demonstrates shorter sleep latencies (i.e., greater physiological sleepiness) as well as the presence of multiple sleep-onset REM periods in individuals with narcolepsy.

Sleep deprivation and insufficient nocturnal sleep

Sleep deprivation and insufficient nocturnal sleep are common in adolescents and shift workers. In adolescents, difficulties falling asleep at night are common, causing sleep deprivation. The MSLT result may be positive if conducted while the individual is sleep deprived or while his or her sleep is phase delayed.

Sleep apnea syndromes

Sleep apneas are especially likely in the presence of obesity. Because obstructive sleep apnea is more frequent than narcolepsy, cataplexy may be overlooked (or absent), and the individual is assumed to have obstructive sleep apnea unresponsive to usual therapies.

Major depressive disorder

Narcolepsy or hypersomnia may be associated or confused with depression. Cataplexy is not present in depression. The MSLT results are most often normal, and there is dissociation between subjective and objective sleepiness, as measured by the mean sleep latency during the MSLT.

Conversion disorder (functional neurological symptom disorder)

Atypical features, such as long-lasting cataplexy or unusual triggers, may be present in conversion disorder (functional neurological symptom disorder). Individuals may report sleeping and dreaming, yet the MSLT does not show the characteristic sleep-onset REM period. Full-blown, long-lasting pseudocataplexy may occur during consultation, allowing the examining physician enough time to verify reflexes, which remain intact.

Attention-deficit/hyperactivity disorder or other behavioral problems

In children and adolescents, sleepiness can cause behavioral problems, including aggressiveness and inattention, leading to a misdiagnosis of attention-deficit/hyperactivity disorder.

Seizures

In young children, cataplexy can be misdiagnosed as seizures. Seizures are not commonly triggered by emotions, and when they are, the trigger is not usually laughing or joking. During a seizure, individuals are more likely to hurt themselves when falling. Seizures characterized by isolated atonia are rarely seen in isolation of other seizures, and they also have signatures on the electroencephalogram.

Chorea and movement disorders

In young children, cataplexy can be misdiagnosed as chorea or pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections, especially in the context of a strep throat infection and high antistreptolysin O antibody levels. Some children may have an overlapping movement disorder close to onset of the cataplexy.

Schizophrenia

In the presence of florid and vivid hypnagogic hallucinations, individuals may think these experiences are real - a feature that suggests schizophrenia. Similarly, with stimulant treatment, persecutory delusions may develop. If cataplexy is present, the clinician should first assume that the symptoms are secondary to narcolepsy before considering a co-occurring diagnosis of schizophrenia.

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