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Narcolepsy

Last updated: March 16, 2021

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Narcolepsy is a neurological disorder of the sleep-wake cycle characterized by excessive daytime sleepiness, cataplexy, sleep paralysis, and hallucinations upon waking or falling asleep. It most commonly manifests in teens and young adults with excessive daytime sleepiness. Primary narcolepsy is either caused by orexin deficiency (type 1) or is idiopathic (type 2). Secondary narcolepsy can occur as a result of brain damage or other genetic syndromes. Diagnosis requires an established history based on questionnaires or a sleep diary as well as a polysomnogram and multiple sleep latency test or an abnormal orexin A (hypocretin-1) level in the cerebrospinal fluid (CSF). No cure has yet been found, but daytime sleepiness can be managed with CNS stimulants (e.g., modafinil) and a regimen of scheduled naps. Cataplexy, hallucinations, and sleep paralysis are treated with antidepressants or sodium oxybate.

Epidemiological data refers to the US, unless otherwise specified.

Primary narcolepsy

Secondary narcolepsy

  • Excessive daytime sleepiness (EDS): Affected individuals experience an irresistible urge to sleep and sudden, short sleep attacks (< 30 minutes), which may occur in inappropriate situations (e.g., while driving a car).
    • One of the earliest manifestations of narcolepsy
    • Can occur despite adequate sleep
  • Abnormal REM sleep
    • Cataplexy (60–70% of cases): sudden muscle weakness in a fully conscious person, triggered by strong emotions (e.g., laughing, crying)
      • Typically manifests months or even years after EDS
      • The loss of muscle tone is similar to that observed during REM sleep.
      • Typically manifests as partial cataplexy: isolated weakness of distinct muscle groups (e.g., neck muscles weaken and head tilts forward)
      • Usually resolves within a few seconds, at most two minutes
    • Sleep paralysis; (∼ 50% of cases): Complete paralysis occurs for 1–2 minutes after waking or before falling asleep (either during a nocturnal or narcoleptic sleep episode, i.e., begins or ends with REM sleep)
  • Sleep hallucinations
    • Hypnagogic hallucinations; (∼ 50% of cases): vivid, often frightening visual or auditory hallucinations that occur as the patient falls asleep
    • Hypnopompic hallucinations: experienced while waking up (less common than hypnagogic hallucinations)
  • Automatic behavior: During narcoleptic episodes, patients often perform routine repetitive tasks automatically without conscious awareness of their environment.
  • Other: : depression, obesity, impotence or low sex drive, headaches, decreased functional performance

Hypnagogic hallucinations occur while going to sleep.

References:[4][5]

  • Diagnostic criteria [6]
  • History
    • Sleep diary
    • Narcolepsy questionnaires
  • Sleep studies
  • Decreased CSF orexin A levels: supports diagnosis if ≤ 110 pg/mL or < ⅓ of mean values in healthy persons
  • Additional tests
    • Human leukocyte antigen (HLA) haplotype testing: helpful in cases where additional objective evidence of narcolepsy is wanted
    • Diagnostics to rule out secondary narcolepsy (e.g., brain imaging)

General approach

  • Sleep hygiene recommendations
    • Take scheduled naps throughout the day to reduce the urge to sleep.
    • Ensure regular sleep periods during the night.
  • Avoid substances that disturb the sleep-wake cycle (e.g., alcohol, antipsychotics, opiates).
  • Consultations with family and employer (e.g., people with narcolepsy require a place to sleep at their workplace)

Automobile accidents are a concern! Patients should take treatment and be symptom-free to be allowed to drive.

Medical therapy

Choice of medication depends on the occurrence and relative extent of excessive daytime sleepiness, cataplexy, and/or nocturnal sleep disturbances. More than one medication may be required.

Sodium oxybate should never be taken with alcohol or other CNS depressants because doing so may cause life-threatening respiratory depression!

  • No cure available
  • In general, not associated with decreased life expectancy [10]
  • However, increased risk of death due to job-related or motor vehicle accidents [10]
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  2. Chieffi S, Carotenuto M, Monda V, et al. Orexin System: The Key for a Healthy Life. Frontiers in Physiology. 2017; 8 . doi: 10.3389/fphys.2017.00357 . | Open in Read by QxMD
  3. Jennum P. Definition, Epidemiology and Socioeconomic Burden of Narcolepsy. US Neurology. 2008; 04 (01): p.57. doi: 10.17925/usn.2008.04.01.57 . | Open in Read by QxMD
  4. Narcolepsy Fact Sheet. https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Fact-Sheets/Narcolepsy-Fact-Sheet. Updated: January 1, 2017. Accessed: March 29, 2017.
  5. Kim LJ, Coelho FM, Hirotsu C, et al. Frequencies and associations of narcolepsy-related symptoms: a cross-sectional study. J Clin Sleep Med. 2015; 11 (12): p.1377-1384. doi: 10.5664/jcsm.5268 . | Open in Read by QxMD
  6. American Academy of Sleep Medicine. International classification of sleep disorders, 3rd edition. American Academy of Sleep Medicine
  7. Thorpy MJ, Shapiro C, Mayer G, et al. A randomized study of solriamfetol for excessive sleepiness in narcolepsy. Ann Neurol. 2019; 85 (3): p.359-370. doi: 10.1002/ana.25423 . | Open in Read by QxMD
  8. Dauvilliers Y et al.. Pitolisant versus placebo or modafinil in patients with narcolepsy: a double-blind, randomised trial. The Lancet Neurology. 2013; 12 (11): p.1068-1075. doi: 10.1016/s1474-4422(13)70225-4 . | Open in Read by QxMD
  9. Morgenthaler TI, Kapur VK, Brown T, et al. Practice parameters for the treatment of narcolepsy and other hypersomnias of central origin.. Sleep. 2007; 30 (12): p.1705-11. doi: 10.1093/sleep/30.12.1705 . | Open in Read by QxMD
  10. Disorders - Narcolepsy. https://brainfoundation.org.au/disorders/narcolepsy/. . Accessed: February 8, 2021.