Definition of Cataplexy

Cataplexy: A debilitating medical condition in which a person suddenly feels weak and collapses at moments of strong emotion such as laughter, anger, fear or surprise. In so collapsing, people with cataplexy may injure themselves.

Laughter and other emotions trigger a reflex in persons that can bring many of the muscles of the body to the point of collapse. The phenomenon can be measured by sending electric signals through the muscles and gauging their response. In cataplexy, what is known as the H-reflex, a neurological pathway that causes muscle contractions, virtually disappears.

Cataplexy often affects people who have narcolepsy, a disorder in which there is great difficulty remaining awake during the daytime.

The word "cataplexy" comes from the Greek "kata" meaning "down" + "plexis" meaning a stroke or seizure = a falling-down seizure.