Narcolepsy

Description

Narcolepsy is a disorder characterised by daily periods of irrepressible need to sleep or daytime lapses into sleep occurring for at least several months, accompanied by abnormal manifestations of REM sleep. Multiple sleep latency testing (MSLT) demonstrates a mean sleep latency of <8 minutes and two or more sleep-onset REM periods (SOREMP’s), or one or more SOREMP’s on MSLT and a SOREMP on the preceding overnight polysomnography (PSG). Nighttime sleep is often disturbed, and brief daytime naps are typically refreshing. [1]

Subcategories

• 7A20.0 Narcolepsy, Type 1

  Type 1 narcolepsy is a disorder of excessive sleepiness due to a deficiency of hypothalamic hypocretin (orexin) signaling. In addition to daily periods of irrepressible need to sleep or daytime lapses into sleep, type 1 narcolepsy is characterised by symptoms of REM sleep dissociation, most importantly cataplexy. Cataplexy is a sudden and uncontrollable loss of muscle tone arising during wakefulness that is typically triggered by a strong emotion, such as excitement or laughter. Although cataplexy is a pathognomonic symptom of type 1 narcolepsy, it may not manifest until years following onset of the sleepiness. In such cases, a diagnosis of narcolepsy, type 1 may be made based on cerebrospinal fluid (CSF)-hypocretin levels < 110 picograms per milliliter. Episodes of sleep paralysis and hypnagogic or hypnopompic hallucinations may also be present. The disorder is not attributable to a disease of the nervous system or other medical condition. Note: A definitive diagnosis requires daily periods of irrepressible need to sleep or daytime lapses into sleep plus either: a) cataplexy and multiple sleep latency test/polysomnography (MSLT/PSG) findings characteristic of narcolepsy; or b) demonstrated CSF hypocretin deficiency. [1]

• 7A20.1 Narcolepsy, Type 2

  Type 2 narcolepsy is a disorder of excessive sleepiness characterised by daily periods of irrepressible need to sleep or daytime lapses into sleep and abnormal manifestations of REM sleep as demonstrated by multiple sleep latency test (MSLT/PSG) findings in the context of normal hypothalamic hypocretin (orexin) signaling. That is, cerebrospinal fluid (CSF) hypocretin determinations are > 110 picograms per milliliter. Cataplexy is not present. The disorder is not attributable to another disease of the nervous system or other medical condition. Note: A definitive diagnosis requires daily periods of irrepressible need to sleep or daytime lapses into sleep and multiple sleep latency test/polysomnography (MSLT/PSG) findings characteristic of narcolepsy. There should be no evidence of cataplexy or CSF hypocretin deficiency (if testing is performed). [1]

References

1. World Health Organization. International Classification of Diseases, 11th Revision, for Mortality and Morbidity Statistics (ICD-11 MMS), 2026-01 release. World Health Organization; 2026.

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