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Narcolepsy

BASICS

Description

  • Chronic neurologic sleep disorder
  • Key features:
  • Excessive daytime sleepiness (EDS)
  • May include cataplexy (sudden loss of muscle control), hypnagogic/hypnopompic hallucinations, and sleep paralysis
  • Types:
  • Type 1 (with cataplexy, ~60–70%)
  • Type 2 (without cataplexy)
  • No cure; managed symptomatically

EPIDEMIOLOGY

  • Onset: Bimodal; peaks at age 15 and 35 (male > female)
  • Prevalence:
  • Type 1: 25–50/100,000
  • Type 2: 20–34/100,000
  • African Americans: more often without cataplexy and younger onset

ETIOLOGY & PATHOPHYSIOLOGY

  • Degeneration of hypothalamic orexin (hypocretin) neurons
  • 85% loss in type 1, ~33% in type 2
  • Orexin promotes wakefulness; loss leads to sleep–wake cycle disorganization
  • Likely autoimmune; triggers: infection (influenza A, strep), environment
  • Genetics:
  • 98% of type 1 have HLA-DQB1*0602
  • Autosomal recessive pattern; familial cases increased
  • Risk factors:
  • Age, obesity, head trauma, CNS infection, psychological stress, family history, recent influenza/strep/H1N1 vaccine

COMMONLY ASSOCIATED CONDITIONS

  • OSA (up to 25%), obesity, anxiety

DIAGNOSIS

History

  • Classic pentad:
  • EDS (100%—cardinal, usually initial symptom)
  • Cataplexy (65–75%, mostly type 1)
  • Sleep paralysis
  • Hypnagogic/hypnopompic hallucinations
  • Fragmented/disrupted nocturnal sleep
  • Only 10–20% have all five
  • EDS:
  • Present almost daily ≥3 months
  • Sudden sleep attacks (even during activity), refreshing daytime naps
  • Cataplexy:
  • Sudden transient loss of muscle tone (seconds–minutes), emotion-triggered
  • Preserved consciousness, memory
  • Sleep paralysis:
  • Temporary inability to move/speak on waking or falling asleep
  • Awareness maintained
  • Hallucinations:
  • Hypnagogic (on falling asleep) or hypnopompic (on waking)
  • Visual/tactile/auditory, commonly animals attacking
  • Other:
  • Nocturnal insomnia, retrograde amnesia, increased limb movements, weight gain with progression

Physical Exam

  • Usually normal
  • During cataplexy: diminished/absent DTRs

Differential Diagnosis

  • Sleep apnea, idiopathic hypersomnia, psychiatric/medication effects, circadian disorders, cataplexy mimics, poor sleep hygiene, neurologic disorders (e.g., stroke, Parkinson’s)

Pediatric Considerations

  • Rare before age 5; EDS usually OSA, poor sleep hygiene, or developmental
  • Children may gain excessive weight

Diagnostic Tests

  • Sleep log/actigraphy: 6h/night x 7–14d
  • Polysomnography (PSG): rule out other causes
  • Multiple sleep latency test (MSLT):
  • Performed after PSG
  • Positive: mean sleep latency <8 min, ≥2 sleep-onset REM periods
  • Epworth Sleepiness Scale (ESS):

  • 10 suggests sleep disorder

  • CSF orexin (<110 pg/mL): diagnostic, rarely needed
  • HLA typing: supportive, not specific

Type 1 Diagnostic Criteria

  • EDS ≥3 months
  • Cataplexy + positive MSLT or low CSF orexin

Type 2 Diagnostic Criteria

  • EDS ≥3 months
  • No cataplexy or normal orexin

TREATMENT

General Measures

  • Symptomatic control; no cure
  • Sleep hygiene, regular sleep schedule, planned naps (20 min), avoid stimulants and triggers, safety precautions

Medications

First Line

  • EDS:
  • Modafinil (Provigil): 100–400 mg/day
  • Armodafinil (Nuvigil): 150–250 mg QAM
  • Pitolisant (Wakix): up to 35.6 mg
  • Solriamfetol (Sunosi): 75–150 mg/day
  • Cataplexy:
  • Sodium oxybate (Xyrem/Xywav/Lumryz): 6–9 g/day divided doses
  • Clomipramine: 25–75 mg/day
  • Venlafaxine: 75–375 mg/day
  • Fluoxetine: 20–80 mg/day

Second Line

  • EDS:
  • Methylphenidate: up to 60 mg/day
  • Dextroamphetamine: up to 60 mg/day
  • Nocturnal awakenings:
  • Temazepam: 15–30 mg HS

Referral

  • Neurology if unresponsive to primary agents or severe cataplexy

ONGOING CARE

  • Monitor: response, safety, medication effects
  • Education: driving safety, symptom management, support resources

PROGNOSIS

  • Improvement in 60–80% with therapy; may worsen with aging; may improve post-menopause in women

ICD-10 CODES

  • G47.429 Narcolepsy in conditions classified elsewhere w/o cataplexy
  • G47.411 Narcolepsy with cataplexy
  • G47.419 Narcolepsy without cataplexy

Clinical Pearls

  • Narcolepsy: incurable REM disorder, pathognomonic sign is cataplexy
  • Classic tetrad: EDS, cataplexy, sleep paralysis, hypnagogic hallucinations (only cataplexy is pathognomonic)
  • Diagnosis: clinical + PSG/MSLT; orexin/CSF rarely needed
  • Symptoms manageable; patient safety (driving) is critical