What is Cataplexy?
When a person has a cataplectic episode, he experiences a sudden and short-lived episode of muscle weakness on both sides of the body. The muscle weakness occurs despite the fact that the individual remains fully conscious. In other words, he is temporarily paralyzed, but fully awake. These episodes occur during the day and are often triggered by excitement and laughter. While cataplexy is most often associated with narcolepsy[l1] , individuals with some rare disorders such as Prader-Willi Syndrome, Niemann-Pick type C disease, and Wilson’s disease may also commonly experience cataplexy. Cataplexy becomes worse when the individual is tired.
Signs and symptoms
The first signs of cataplexy tend to occur in childhood or adolescence. Individuals with cataplexy experience muscle weakness that can range from a trivial weakness of facial or eye muscles or complete muscle paralysis and collapse. In all cases, the cataplexy attacks resolve on their own, without medical intervention. In some ways, cataplexy resembles a seizure and it can therefore be misdiagnosed as a seizure disorder. One big distinction between a seizure and a cataplexy attack, however, is that seizures can occur at any time (not just during the awake state) and seizures do not have an emotional trigger.
Physicians diagnose cataplexy based upon a patient’s description of symptoms. The severity of cataplexy may be graded on an arbitrary scale, such as: grade 3 = complete loss of posture with fall to the ground; grade 2 = weakness with upright posture maintained by, for example, holding on to a table; grade 1 = momentary weakness without the need to hold on to an object for support.
Unfortunately, experts still lack good measures of cataplexy in children and adolescents, especially in patients who are nonverbal. It can thus be difficult to diagnose cataplexy in these individuals. Absent a good pediatric measure, physicians tend to adapt or modify existing adult measures in an attempt to diagnose in this population. In an acknowledgement that the diagnosis in children may be missed, experts have identified a need to translate the experience of cataplexy into child-friendly language that can be used to query a child about a potential cataplexy episode.
What causes it?
Individuals with cataplexy appear to be unable to regulate sleep and awake states and so the two states may overlap. The result is that individuals with cataplexy may experience the muscular paralysis that is common during dreaming (REM sleep) while they are awake. Cataplexy is associated with damage to nerve cells in a part of the brain known as the hypothalamus. Individuals who experience cataplexy also tend to have disturbances in the levels of the brain chemicals orexin, histamine, and epinephrine.
In some cases, cataplexy may be the result of an autoimmune disorder that targets the orexin neurons in the brain.
Unfortunately, there are no behavioral treatments for cataplexy. Patients must manage their symptoms either with medication or by avoiding triggers such as laughter or excitement. In the United States, only one drug is currently approved for the treatment of cataplexy and that is sodium oxybate.