Cataplexy is a condition in which a person suffers from sudden attacks of muscle weakness that are commonly caused by the experience of a strong emotion, according to Dictionary.com. These attacks often cause the body to helplessly collapse, and they are linked to narcolepsy.
Along with excessive daytime sleepiness, hallucinations and sleep paralysis, cataplexy is a common symptom of narcolepsy. However, the cause of narcolepsy is unknown, as of 2015. In addition to loss of voluntary muscle control, cataplexy may cause slurred speech, loss of muscle tone and a feeling of weakness. Intense emotions such as surprise, laughter and anger are common triggers for cataplexy episodes, according to WebMD.