Cataplexy

Cataplexy
Classification and external resources
Specialty	Neurology
ICD-10	G47.4
ICD-9-CM	347
DiseasesDB	16311
Patient UK	Cataplexy
MeSH	D002385
[]

Cataplexy is a sudden and transient episode of muscle weakness accompanied by full conscious awareness, typically triggered by emotions such as laughing, crying, or terror. It is the cardinal symptom of narcolepsy with cataplexy affecting roughly 70% of people who have narcolepsy, and is caused by an autoimmune destruction of the neurotransmitter hypocretin (also called orexin), which regulates arousal and wakefulness. Cataplexy without narcolepsy is rare and the cause is unknown.

The term cataplexy originates from the Greek κατά (kata, meaning "down"), and πλῆξις (plēxis, meaning "stroke").

Cataplexy manifests itself as muscular weakness which may range from a barely perceptible slackening of the facial muscles to complete muscle paralysis with postural collapse. Attacks are brief, most lasting from a few seconds to a couple of minutes, and typically involve dropping of the jaw, neck weakness, and/or buckling of the knees. Even in a full-blown collapse, people are usually able to avoid injury because they learn to notice the feeling of the cataplectic attack approaching and the fall is usually slow and progressive. Speech may be slurred and vision may be impaired (double vision, inability to focus), but hearing and awareness remain normal.

Cataplexy attacks are self-limiting and resolve without the need for medical intervention. If the person is reclining comfortably, he or she may transition into sleepiness, hypnagogic hallucinations, or a sleep-onset REM period. While cataplexy worsens with fatigue, it is different from narcoleptic sleep attacks and is usually, but not always, triggered by strong emotional reactions such as laughter, anger, surprise, awe, and embarrassment, or by sudden physical effort, especially if the person is caught off guard. One well known example of this was the reaction of 1968 Olympic long jump medalist Bob Beamon on understanding that he had broken the previous world record by over 0.5 meters (2 feet). Cataplectic attacks may also occur spontaneously with no identifiable emotional trigger.

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