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Glossary

Terms and phrases to help know narcolepsy.

Know Narcolepsy provides important information and resources to help people living with narcolepsy, and their friends and family, understand symptoms and their impact, communicate with healthcare professionals, and create strategies and tips for managing the day to day with narcolepsy.

Automatic behavior -

Performance of routine tasks (e.g., writing, cooking) without awareness or memory.

Brain fog -

A commonly used phrase to describe difficulty focusing or concentrating; confusion.

Cataplexy -

Sudden and brief loss of muscle strength or tone (e.g., knees buckling, jaw sagging) with retained awareness, often triggered by strong emotions. Only occurs in people with narcolepsy, but not every person with narcolepsy has cataplexy. Narcolepsy with cataplexy is known as type 1 narcolepsy.

Complete Cataplexy -

Complete collapse to the ground; usually takes several seconds to develop and all muscles are involved.

Partial Cataplexy -

Only certain muscle groups are involved; facial, head, or neck weakness are common.

Disrupted nighttime sleep -

Frequent shifts between different states of sleep and wakefulness that occur at night, causing poor-quality sleep. These disruptions significantly decrease restorative sleep stages.

Excessive daytime sleepiness -

The inability to stay awake and alert during the day, resulting in a constant and uncontrollable need for sleep or unintentionally falling asleep. The primary symptom of narcolepsy.

Histamine -

A chemical in the brain that helps maintain wakefulness. When histamine levels are high, people are typically awake.

Hypnagogic/hypnopompic hallucinations -

Vivid, realistic, and usually frightening dream-like events that occur when falling asleep. When they occur while waking up, they are called hypnopompic hallucinations.

Hypocretin -

A chemical in the brain that helps maintain wakefulness and prevent non-REM sleep and REM sleep from occurring at the wrong time. Low levels of hypocretin cause the separate states of wakefulness and sleep to not work properly, shifting often from one state to another, leading to symptoms of narcolepsy.

Involuntary sleep -

Unintentionally falling asleep due to excessive daytime sleepiness. Also known as “sleep attacks.”

Non-REM sleep -

A state of sleep when muscle tone or tension is decreased. It is made up of different stages. Deep stages help to restore the body. People usually wake up more easily from light non-REM sleep than from deep non-REM sleep.

REM sleep -

Rapid eye movement sleep; normally occurs at night and includes vivid dreams. Most muscles are not active to prevent people from acting out their dreams.

Sleep hygiene -

Daytime and evening habits and routines to help improve sleep.

Sleep paralysis -

Brief total loss of control of voluntary muscles when people are typically fully aware of what is going on around them. Occurs when falling asleep or while waking up, and can be frightening.

Type 1 narcolepsy -

Also often called narcolepsy with cataplexy. People with type 1 narcolepsy can be diagnosed by their cataplexy or, if measured, by low levels of hypocretin.

Type 2 narcolepsy -

Also called narcolepsy without cataplexy. The cause of type 2 narcolepsy is unknown.

Performance of routine tasks without awareness or memory.

Difficulty focusing or concentrating.

Brief loss of muscle tone with retained awareness, often triggered by strong emotions.

Frequent shifts between different states of sleep and wakefulness at night.

The inability to stay awake and alert during the day; a constant need for sleep or unintentionally falling asleep.

A chemical in the brain that helps maintain wakefulness.

Vivid, realistic, and frightening dream-like events that occur when falling asleep.

Dream-like events that occur when falling asleep. Called hypnopompic hallucinations if they occur when waking up.

A chemical in the brain that helps maintain wakefulness and prevent non-REM sleep and REM sleep from occurring at the wrong time.

Unintentionally falling asleep due to excessive daytime sleepiness; “sleep attacks.”

Restorative sleep state with decreased muscle tone.

Occurs at night and includes vivid dreams; muscles are not active to prevent people from acting out dreams.

Daytime and evening habits to improve sleep.

Brief total loss of voluntary muscle control when falling asleep or while waking up.

People with type 1 narcolepsy can be diagnosed by their cataplexy or low levels of hypocretin.

The cause of type 2 narcolepsy is unknown.