Cataplexy is a sudden, brief loss of voluntary muscle tone triggered by strong emotions such as laughter.
The condition is most commonly associated with narcolepsy, a sleep disorder affecting less than 1% of the general population.
Cataplexy occurs during waking hours. Attacks can be a barely visible weakness in a muscle, such as drooping of the eyelids, or as severe as a total body collapse. As cataplexy is a neurological problem, it can be misdiagnosed as a seizure disorder.
There is no cure for cataplexy, but it can be managed with medications and modification of potential triggers.
Contents of this article:
Fast facts on cataplexy
Here are some key points about cataplexy. More detail and supporting information is in the main article.
- During an episode of cataplexy, an individual is awake but temporarily paralyzed (either partially or fully)
- The brain's amygdala and prefrontal cortex contain neural pathways through which positive emotions are suspected to trigger cataplectic attacks
- Narcolepsy with cataplexy is currently thought to be an autoimmune-mediated disorder
- Cataplexy without narcolepsy is rare
- Onset of cataplexy typically occurs in childhood or adolescence
- Cataplexy is worsened by fatigue
- Cataplexy affects males and females equally
- Cataplexy can occur after the abrupt discontinuation of an antidepressant medication
- One difference between a seizure and cataplexy is that a seizure can occur at any time and is not primarily triggered by periods of strong emotion
- Sodium oxybate is approved by the US Food and Drug Administration (FDA) for the treatment of cataplexy
- The word cataplexy means "to strike down."
What is cataplexy?
During an episode of cataplexy, the individual can lose muscle control on both sides of the body, occasionally leading to full body collapse.
Cataplexy is a sudden loss of muscle control, usually on both sides of the body, triggered by strong, often pleasant emotions. While laughter is the most typical trigger, other triggers may include happiness, excitement, annoyance, surprise or a stressful event.
Cataplexy is most often associated with narcolepsy, but can occur with other rare disorders such as Niemann-Pick type C disease, Prader-Willi syndrome and Wilson's disease.
The duration of a cataplexy attack is brief, lasting anywhere from a few seconds to several minutes, followed by a rapid return of normal muscle tone and function.
Causes of cataplexy
The REM sleep disassociation hypothesis suggests that cataplexy is the muscle paralysis that normally occurs during REM sleep intruding into waking hours. The underlying cause of this intrusion is unknown, but a loss of hypocretin (also known as orexin), a neurotransmitter involved in the regulation of the sleep/wake cycle, is thought to be the major contributing factor.
A study published in the Journal of Clinical Investigation in 2010 revealed that the loss of hypocretin is caused by an autoimmune response targeting tribbles, or trib 2 antibodies. This autoimmune response also kills neurons in the brain that produce hypocretin.
The frequency of cataplectic episodes varies from less than one per year to several per day, with the average person affected by cataplexy experiencing one or more per week.
Symptoms of cataplexy
Cataplectic attacks have a wide range of variability; they may be mild and barely noticeable or severe with full body collapse.
Cataplexy episodes may include:
- Facial twitching, flickering or grimacing
- Unusual tongue movements
- Jaw tremor
- Head or jaw dropping
- Knee trembling or buckling
- Drooping eyelid
- Speech difficulty.
It is important to note an individual experiencing cataplexy remains conscious, is able to breathe and can move their eyes.
On the next page, we look at the diagnosis of cataplexy and the available treatment options for the condition.