The Four Defining Features and Classic Symptoms of Narcolepsy

Learn More About Sleepiness, Hallucinations, Sleep Paralysis, and Cataplexy

Narcolepsy is a disorder most commonly characterized by excessive daytime sleepiness, but it also has other symptoms that make up the four defining features that make it unique among the sleep disorders. Though only one in three people with narcolepsy have all four features, they can be useful in identifying those at risk for the disorder. What are these defining features or classic symptoms of narcolepsy? Learn about daytime sleepiness, hallucinations, sleep paralysis, and cataplexy.

1
Excessive Daytime Sleepiness

Excessive daytime sleepiness is one of the defining features of narcolepsy
Excessive daytime sleepiness is one of the defining features of narcolepsy. Ghislain & Marie David de Lossy/Getty Images

This is the increased desire to fall asleep and lack of energy during the day even after an adequate night's sleep. In narcolepsy, sleep begins to intrude upon wakefulness, and elements of wakefulness intrude upon sleep. Therefore, narcoleptics are prone to falling asleep at all times with little warning (so-called "sleep attacks").

Sleep overnight may be disturbed as well. People with narcolepsy are more likely to go into rapid eye movement (REM) sleep within the first hour after falling asleep (and often within the first 15 minutes). In addition, sleep is more fragmented with frequent transitions between sleep stages.

The daytime sleepiness may result in double or blurred vision and automatic behaviors such as "zoning out" while driving. The Epworth sleepiness scale identifies the degree of excessive sleepiness and scores higher than 15 out of 24 are often reported by narcoleptics. The sleepiness in narcolepsy typically improves after a brief nap. In addition, narcoleptics typically wake up feeling refreshed in the morning.

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2
Hypnagogic Hallucinations

Hypnagogic hallucinations are one of the defining features of narcolepsy
Hypnagogic hallucinations are one of the defining features of narcolepsy. Zigy Kaluzny/The Image Bank/Getty Images

These involve vivid, often frightening hallucinations that occur in the transitions between sleep and wakefulness. This is most often as the person is falling asleep or waking up. Hypnagogic hallucinations result when REM sleep and the associated dreaming mixes with wakefulness. These hallucinations are often visual, but other experiences may occur as well.

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3
Sleep Paralysis

Sleep paralysis is one of the defining features of narcolepsy
Sleep paralysis is one of the defining features of narcolepsy. Vladimir Godnik/Getty Images

Sleep paralysis is a common experience that may occur normally in people, but it can also be found in narcolepsy. It consists of the inability to move for one or two minutes upon awakening. There may be accompanying feelings of suffocation or even a presence within the room. The episodes tend to be quite frightening. Though they may occur in normal people, especially during sleep disruptions, they also are a sign of narcolepsy.

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4
Cataplexy

Cataplexy, or loss of muscle tone with emotion, is one of the defining features of narcolepsy
Cataplexy, or loss of muscle tone with emotion, is one of the defining features of narcolepsy. Science Photo Library/Getty Images

Finally, cataplexy is the sudden and transient loss of muscle tone that is triggered by an emotional event. For example, laughter, joking, or excitement may cause a temporary weakness. This weakness may only involve a part of the body, such as the face, neck, or knees and recovery may be quick. It typically lasts only a few minutes and consciousness remains intact. Severe episodes may cause falls.

Interestingly, cataplexy occurs in almost no other disorder, so if it is present, narcolepsy with cataplexy (or type 1 narcolepsy) is the likely diagnosis. Its presence again relates to an intrusion of REM sleep into wakefulness, for paralysis normally occurs when we are asleep so that we do not act out our dreams.

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