Narcolepsy

Last updated: March 23, 2022

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Narcolepsy is a neurological disorder of the sleep-wake cycle characterized by excessive daytime sleepiness and, in some cases, cataplexy, sleep paralysis, and hallucinations upon waking or falling asleep. It most commonly manifests in teenagers and young adults. Primary narcolepsy type 1 may manifest with cataplexy and/or orexin deficiency. Patients with type 2 primary narcolepsy have normal orexin levels. Secondary narcolepsy can occur as a result of brain damage or genetic syndromes. Diagnosis requires a history ≥ 3 months of excessive daytime sleepiness and either typical findings on polysomnography or an abnormal level of hypocretin-1 (orexin A) in the cerebrospinal fluid (CSF). There is no cure for narcolepsy but daytime sleepiness can be managed with optimized sleep hygiene and CNS stimulants 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: 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: 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
  • 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.

Approach [8][9][10]

Diagnostic criteria [8][10][11]

Sleep studies [12]

  • Daytime multiple sleep latency test (MSLT)
    • Includes 5 opportunities for the patient to nap during the daytime and measures :
      • Sleep latency: time needed to fall asleep
      • Sleep-onset REM periods (SOREMPs): REM periods that occur within 15 minutes of falling asleep; also referred to as shortened REM sleep latency
    • Characteristic findings
  • Nocturnal polysomnography (PSG)
    • Measures sleep duration, efficiency, and stages
    • Used to exclude other sleep disorders and may also show supportive findings for narcolepsy (e.g., SOREMP)

If feasible, medications affecting sleep (e.g., antidepressants and stimulants) should be paused for at least two weeks prior to a sleep study. [12]

Additional tests

General measures

  • Optimize sleep hygiene. [9]
    • Ensure regular sleep periods during the night.
    • Avoid substances that disturb the sleep-wake cycle (e.g., alcohol, antipsychotics, opiates).
  • Consider scheduled naps throughout the day to reduce the urge to sleep. [16]

As motor vehicle collisions are a concern for patients with narcolepsy, to be allowed to drive, they should be symptom-free and taking treatment. State regulations vary on the legally required period of time that patients should be symptom-free before driving.

Medical therapy [17]

Principles of medical therapy

Commonly used agents

Sodium oxybate (gamma-hydroxybutyrate) may cause life-threatening respiratory depression and should never be taken with alcohol or other CNS depressants. Since it is used recreationally to induce sedation and euphoria, sodium oxybate has a high potential for misuse. [17]

Stimulants recommended for treating narcolepsy may cause fetal harm and reduce the effectiveness of oral contraception. [17]

  • Currently no cure available [16]
  • Associated with higher rates of morbidity (e.g., cardiovascular disease) [21][22]
  • Increased risk of motor vehicle accidents (adequate treatment may mitigate risk) [23]
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