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.
[1] Cataplexy is the first symptom to appear in about 10% of cases of narcolepsy,[2] 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.
[4] 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.
[7] 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.
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.
[9] One well-known example of this was the reaction of 1968 Olympic long jump medalist Bob Beamon on learning that he had broken the previous world record by over 0.5 meters (almost 2 feet).
Other conditions in which cataplexy can be seen include ischemic events, multiple sclerosis, head injury, paraneoplastic syndromes, infections such as encephalitis, and more rarely Niemann Pick disease.
Cataplexy may also occur transiently or permanently due to lesions of the hypothalamus that were caused by surgery, especially in difficult tumor resections.
Hypocretin deficiency is further associated with decreased levels of histamine and epinephrine, chemicals important in promoting wakefulness, arousal and alertness.
[8] Monoamine oxidase inhibitors may be used to manage both cataplexy and the REM sleep-onset symptoms of sleep paralysis and hypnagogic hallucinations.
[22][23][24] Frequently, tolerance is developed by the patients and typically the risk of cataplexy rebound or "status cataplecticus" appears when their intake is abruptly interrupted.
Immunological therapies developed include:[20] The histaminergic neurons have a very important role in preserving consciousness and in helping maintain wakefulness and remain active during cataplexy.
[17] Also placebo-controlled studies suggest some positive effects of Pitolisant on cataplexy symptoms increasing the levels of alertness and wakefulness.
