Narcolepsy and excessive daytime sleepiness: diagnostic considerations, epidemiology, and comorbidities.

Narcolepsy is a chronic, neurologic disorder that has severe disabling effects on affected patients. It usually becomes manifest between the ages of 10 and 25 years and is recognized by a tetrad of symptoms that includes excessive daytime sleepiness, cataplexy, sleep paralysis, and hypnagogic hallucinations. Excessive daytime sleepiness is common and associated with a broad range of medical, sleep, and psychiatric disorders; therefore, accurate diagnosis of narcolepsy and comorbid disorders is important for optimal treatment response.