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- Narcolepsy is characterized by impaired sleep and wakefulness, along with rapid eye movement (REM) sleep abnormalities.
- The clinical tetrad includes the following, although only 10% of those affected will have all 4 symptoms:
- Excessive daytime sleepiness
- Hallucinations occurring at the transition from wakefulness to sleep (hypnagogic)
- Sleep paralysis
- Disrupted nighttime sleep is common, but 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 requires the presence of cataplexy or decreased CSF hypocretin (orexin) levels.
- Type 2 narcolepsy 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) .