cataplexy

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. Cataplexy is the first symptom to appear in about 10% of cases of narcolepsy, caused by an autoimmune destruction of hypothalamic neurons that produce the neuropeptide hypocretin (also called orexin), which regulates arousal and has a role in stabilization of the transition between wake and sleep states. 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 "strike") and it was first used around 1880 in German physiology literature to describe the phenomenon of tonic immobility also known as "playing possum" (in reference to the opossum's behavior of feigning death when threatened). In the same year the French neuropsychiatrist Jean-Baptiste Gélineau coined the term 'narcolepsy' and published some clinical reports that contained details about two patients who had similar conditions to those of current narcoleptic cases. Nevertheless, the onset that he reported was in adulthood, as compared to current cases reported in childhood and adolescence. Even if he preferred the term 'astasia' instead of 'cataplexy', the case that he described remains iconic for the diagnosis of full narcoleptic syndrome.