The main characteristic of narcolepsy is excessive daytime sleepiness (EDS), even after adequate nighttime sleep. A person with narcolepsy is likely to become drowsy or fall asleep or just be very tired throughout the day. Daytime naps may be physically irresistible. These naps can occur several times a day. They are typically refreshing, but only for a few hours. In addition, nighttime sleep may be fragmented with frequent awakenings.
Four of the other classic symptoms of narcolepsy are cataplexy, sleep paralysis, hypnagogic hallucinations, and automatic behavior. These symptoms may not occur in all patients.
Cataplexy is an episodic condition featuring loss of muscle function, ranging from slight weakness to complete body collapse. Episodes may be triggered by sudden emotional reactions such as laughter, anger, surprise, or fear, and may last from a few seconds to several minutes. This is often frightening but is not dangerous. Hypnagogic hallucinations are vivid, often frightening, dreamlike experiences that occur while dozing, falling asleep or while awakening.
There are wide variations in the development, severity, and order of appearance of cataplexy, sleep paralysis, and hypnagogic hallucinations in individuals.
Diagnosis is relatively easy when all the symptoms of narcolepsy are present. Two tests that are commonly used in diagnosing narcolepsy are the polysomnogram and the multiple sleep latency test (MSLT). These tests are usually performed by a sleep specialist.
