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NeurologicalICD-10: G47.4Affects about 1 in 2,000 people in the United States

Narcolepsy

Also known as: Narcolepsy Type 1, Narcolepsy Type 2

Narcolepsy is a chronic neurological disorder that impairs the brain's ability to regulate sleep-wake cycles, causing overwhelming daytime drowsiness and sudden attacks of sleep. Type 1 narcolepsy includes cataplexy (sudden loss of muscle tone triggered by emotions), while Type 2 does not. The condition is caused by a deficiency of the neurotransmitter hypocretin (orexin) and typically begins in childhood or young adulthood.

Symptoms

Excessive daytime sleepiness despite adequate nighttime sleep
Sudden sleep attacks at inappropriate times
Cataplexy — sudden muscle weakness triggered by laughter or strong emotion (Type 1)
Sleep paralysis (inability to move or speak while falling asleep or waking up)
Hypnagogic or hypnopompic hallucinations
Fragmented nighttime sleep
Automatic behaviors (continuing tasks without awareness)

Causes

  • Loss of hypocretin (orexin)-producing neurons in the hypothalamus
  • Autoimmune destruction possibly triggered by infection (H1N1, streptococcus)
  • Genetic factors (strong association with HLA-DQB1*0602)
  • Rarely, brain injuries or tumors affecting the hypothalamus

Risk Factors

  • Family history of narcolepsy
  • Age 10–30 at symptom onset
  • Carrying the HLA-DQB1*0602 gene variant
  • History of certain infections (H1N1 influenza, streptococcal infections)

Diagnosis

  • Polysomnography (overnight sleep study)
  • Multiple Sleep Latency Test (MSLT) showing rapid-onset REM sleep
  • Measurement of hypocretin levels in cerebrospinal fluid (for Type 1)
  • Sleep diary and Epworth Sleepiness Scale assessment

Treatment

  • Wake-promoting agents (modafinil, armodafinil, solriamfetol)
  • Sodium oxybate (Xyrem) for cataplexy and disrupted nighttime sleep
  • Pitolisant (histamine-3 receptor inverse agonist)
  • Scheduled short naps during the day
  • Antidepressants (venlafaxine, fluoxetine) for cataplexy in some patients
  • Lifestyle modifications (regular sleep schedule, good sleep hygiene)

Prevention

  • No known prevention for narcolepsy
  • Early diagnosis and treatment can significantly improve quality of life

When to See a Doctor

  • Persistent excessive daytime sleepiness interfering with work or school
  • Episodes of sudden muscle weakness with strong emotions
  • Falling asleep involuntarily during activities like driving or talking
  • Sleep paralysis or vivid hallucinations during sleep transitions

Frequently Asked Questions

Related Conditions

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Sleep Apnea

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Depression

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