Cataplexy is a sudden loss of muscle control ranging from slight weakness - including head droop, facial sagging, jaw drop, slurred speech and buckling of knees - to total collapse. It is commonly triggered by intense emotion - such as laughter, anger, surprise and fear - and athletics or other strenuous activities. This loss of muscle tone is due to the body lapsing into certain stages of REM sleep, when all of our muscles are “switched off”. Cataplectic attacks usually only last for one to several minutes, during which the person remains fully conscious.
Although the sleep related problems are the most common symptoms of narcolepsy, most of the research on the disease focuses on cataplexy. This is due to the fact that in narcolepsy, only the amount of sleepiness or somnolence is abnormal, and it is hard to tell (especially in animal research models) when episodes of sleepiness are actually 'abnormal'. Cataplexy, however, never occurs in 'normal' subjects, and can also be easily measure in terms of the duration of each attack and the clear electrical changes in the brain that accompany such episodes.
Watch a video (avi format, best viewed with Windows Media Player) of a cataplectic attack in a human adult male, triggered by the sudden movement and emotional excitement produced by playing a game. (This video is courtesy the Center of Narcolepsy at the Stanford School of Medicine.)
Watch a video (mpeg format, best viewed with Windows Media Player) of a cataplectic attack in a 3 year old narcoleptic weimaraner with a marked hypocretin deficiency, when he is excited by the sight and smell of food. (This video is courtesy the Center of Narcolepsy at the Stanford School of Medicine, and was filmed as part of the work of the research team headed by Dr. Emmanuel Mignot.)
The picture at the top of this page is of a cataplectic bulldog. To find out more about canine narcolepsy, see Mignot's Work with Canine Narcolepsy under the Causes section.