Cataplexy Overview: Definition, Symptoms, and Causes

Cataplexy is a physical reaction defined by sudden muscle weakness and a decrease in muscle tone that renders a person unable to exert complete muscle control. Positive, strong emotions like surprise and happiness usually trigger a cataplexy episode. Depending on the severity of the case, someone experiencing cataplexy may simply notice the sudden weakness of a part of their body or can experience a total inability to move.

Someone experiencing cataplexy is fully conscious and aware during an episode. In this way, cataplexy differs from sleep paralysis, which involves a person being in a state of mixed consciousness while experiencing a temporary inability to move or speak while either falling asleep or waking up.

The difference between cataplexy and narcolepsy is that the former is just one of the latter's symptoms (more specifically, Type 1 narcolepsy). Narcolepsy is a neurological sleep disorder in which the brain struggles to control sleep-wake cycles. People with narcolepsy may experience extreme daytime sleepiness, involuntary “sleep attacks,” cataplexy, or stressful sleep paralysis or hallucinations.

Although narcolepsy-cataplexy is common, cataplexy may also have links to other disorders and diseases.

People with cataplexy experience a sudden loss of muscle control or muscle weakness. The frequency of cataplectic episodes can vary widely from multiple times a day to a few rare instances throughout someone’s lifetime.

Cataplexy results from a lack of brain cells that produce the hormone orexin (also known as hypocretin-1 and -2). Orexin is vital in promoting healthy REM sleep (deep sleep characterized by rapid eye movement) since its reuptake by hypocretin receptors increases one’s wakefulness.

There are numerous reasons why someone with cataplexy may lose hypocretin neurons in their hypothalamus. In some cases, it may be genetic. In others, cataplexy begins after a brain injury that puts brain cells out of commission. Cataplexy can also occur due to an autoimmune disease that triggers the body to attack its immune system and destroy those orexin producers.

Medical professionals use a polysomnogram (PSG) and multiple sleep latency tests (MSLT) to diagnose narcolepsy; however, there are no formal tests to detect cataplexy alone. Instead, a doctor may ask about cataplectic attacks in the same questionnaire used to determine if someone is experiencing a sleep disorder like sleep apnea. Typical red flags include abnormalities in a patient’s sleep habits, excessive daytime sleepiness, or a recent change in medication.

While there is no way to increase the number of hypocretin neurons someone has, doctors may prescribe tricyclic antidepressants or selective serotonin reuptake inhibitors (SSRIs) to treat narcolepsy and cataplexy. (Increasing the levels of norepinephrine and serotonin can help stave off possible paralysis.) Doctors may also prescribe a form of the depressant GHB (gamma hydroxybutyrate) called sodium oxybate that serves as a sleep medicine and decreases the risk of cataplexy.

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