DEFINITION

• Narcolepsy is characterized by impaired sleep and wakefulness, along with rapid eye movement (REM) sleep abnormalities.
• The clinical pentad includes the following, although only 10% of those affected will have all 5 symptoms:
  • Excessive daytime sleepiness
  • Hallucinations occurring at the transition from wakefulness to sleep (hypnagogic)
  • Sleep paralysis
  • Cataplexy
  • Disrupted nocturnal sleep
• The most disabling symptoms are daytime inattention and hypersomnolence.
  
  • Especially during sedentary activities
  • Sometimes with irrepressible sleep attacks
• Cataplexy is a brief (usually less than 2 minutes) symmetrical sudden loss of muscle tone with preserved consciousness, typically precipitated by strong emotions (especially laughter).
  • Episodes may range from very subtle (e.g., neck or jaw weakness) to complete collapse.
• Type 1 narcolepsy (NT1) requires the presence of cataplexy or decreased CSF hypocretin (orexin) levels.
• Type 2 narcolepsy (NT2) involves abnormalities evident upon nighttime and daytime sleep laboratory testing.
• Narcolepsy is classified under the Sleep-Wake Disorders section of the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5)[1].