Medical Terms:

Narcolepsy: (abbrev: N) If you’re here, chances are you already know something about narcolepsy, but there’s so much to know! Briefly put, narcolepsy is a sleep disorder that is characterized by extreme daytime sleepiness (often with urge to sleep coming in crushing waves), a sudden onset of rapid eye movement (abbrev: REM sleep or simply REM) sleep and a corresponding decrease in slow wave sleep, and often accompanied with a symptom known as cataplexy, a sudden loss of muscle tone. More at

Cataplexy: (abbrev: C) Mentioned above, cataplexy is a symptom seen in roughly 2/3 of all narcolepsy patients. This is characterized by a sudden loss of muscle tone, which can range from slight (dropping something one is holding) to severe (collapsing to the ground or slumping over in a chair). This is often preceded by a strong emotional reaction, like fear, surprise, laughter, sadness, or anger. To learn more, visit

REM Sleep: A stage of deep sleep characterized by increased brain activity, vivid dreams, and loss of muscle tone. Most of the dreams a person can remember occur during REM sleep. Learn more at

REM Atonia: The loss of muscle tone the body undergoes during REM sleep. Cataplexy is thought to be the result of REM atonia intruding into wakeful states.

Hypersomnia: A syndrome describing increased sleep duration and frequency by a patient.

Idiopathic Hypersomnia: (abbrev: IH) A hypersomnia with no discernible cause. Many suspected cases of narcolepsy are eventually labeled idiopathic hypersomnia if the diagnostic criteria of narcolepsy (such as the REM anomalies or cataplexy) cannot be conclusively established. More at:

Hypnagogic/Hypnopompic Hallucinations: (abbrev: HH) Fragmented hallucinations that occur upon entering/exiting sleep. Often, for brevity’s sake, the term hypnagogic is used to refer to both cases. These hallucinations can range from mundane to terrifying.

Sleep Paralysis: (abbrev: SP) A condition that can occur upon entering or exiting sleep where the body mistakenly enters REM atonia. SP is often accompanied with hypnagogic hallucinations.

Orexin/Hypocretin: The neurochemical in the brain thought to be deficient or malfunctioning in those suffering from narcolepsy. Read more at

Polysomnography: (abbrev: PSG) Also known as a sleep study, this is one of two tests commonly used to diagnose Narcolepsy. An EEG and other sensors are used to record movement and brain activity during nighttime sleep. When examining a PSG result, a sleep specialist looks for signs of other possible explanations of symptoms, as well as certain hallmarks of N such as decreased REM latency and frequent arousals. Find out more:

Multiple Sleep Latency Test: (abbrev: MSLT) This test is performed the following morning after a PSG, if the PSG showed signs of narcolepsy without any offering any other possible explanations for the patient’s symptoms.  Once again the EEG is used to record brain wave activity, and the patient is asked to take a series of naps in order to measure REM latency. An MSLT indicating narcolepsy, along with a PSG that does not indicate other sleep disorders, is usually required for diagnosis of N, unless cataplexy is demonstrated in office. More at:

Maintenance of Wakefulness Test: (abbrev: MWT) This third test is sometimes performed in order to determine the severity of a patient’s symptoms. Patients are again connected to an EEG and placed in a dark room and made to lie down and be still. This test measures how sleepy a patient is by determining how long it takes them to fall asleep, once given the ideal conditions to do so.

Additional Acronyms:

N w/C or Type 1 N: Narcolepsy with cataplexy. This is the most common form of narcolepsy.

N w/o C or Type 2 N: Narcolepsy without cataplexy.

PWN: People with Narcolepsy.

EDS: Extreme daytime sleepiness

SOREM/SOREMP: Sudden onset REM (period)

Dx/Rx/Tx: Diagnosis/Prescription/Treatment