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:
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.
Tests and diagnosis of cataplexy
There is no specific diagnostic test for cataplexy. Instead, a diagnosis is based on the patient's description of events and history.
Often, an individual presents to a medical provider with the complaint of excessive daytime sleepiness (EDS), or a persistent background feeling of sleepiness during waking hours. Because EDS is a common problem, the diagnosis of cataplexy can be difficult to make, and is often delayed by many years after the initial symptom onset.
Individuals who have EDS or symptoms of cataplexy should see their medical provider. A sleep study (polysomnography) will most likely be ordered by the provider, followed by a Multiple Sleep Latency Test (MSLT) - a series of five naps scheduled to be taken over the course of a day.
Carrying out the MSLT the day after polysomnography enables doctors to find out whether or not the sleep obtained the previous night has any affect on daytime napping.
Treatment and prevention of cataplexy
There is no cure for cataplexy, and treatment is symptom management with good sleep hygiene practices and the use of medication as necessary. Additionally, safety measures should be put in place to avoid any serious injury from falls.
Good sleep hygiene practices include:
- Keeping a consistent sleep schedule - get up and go to bed at the same time every day, even on weekends or during vacations
- Striving for at least 7 hours of sleep, or the amount that normally makes you feel refreshed
- Making your bedroom quiet and relaxing - keep the room at a comfortable, cool temperature
- Limiting exposure to light in the evenings
- Exercising regularly and maintaining a healthy diet
- Avoiding a large meal before bedtime - if you are hungry at night, eat a light, healthy snack
- Avoiding consumption of caffeine in the late afternoon or evening
- Avoiding alcohol
- Scheduling one or more short naps during the day.
Sodium oxybate at doses between 4.5 and 9 g nightly is the medication approved by the FDA for the treatment of cataplexy. Sodium oxybate is effective in reducing both the frequency and intensity of attacks.
Possible adverse effects are dizziness, headache and nausea. This medication should not be used in conjunction with alcohol or any other central nervous system (CNS) depressant due to the risk of respiratory depression.
Other medications that may help control symptoms are venlafaxine, a serotonin-noradrenaline reuptake inhibitor (SNRI) antidepressant, and tricyclic antidepressants such as clomipramine, imipramine and desipramine. However, abrupt withdrawal of venlafaxine can cause rebound cataplexy.
In regards to safety, even if an individual senses the onset of an episode, injury is common with cataplexy.
Avoiding sleep deprivation can reduce the risk of injury occurring with cataplexy.
To help avoid injury from occurring with cataplexy:
- Assess for and be aware of potential dangers such as glass, sharp edges and heights
- Practice relaxation and stress management techniques
- Avoid sleep deprivation
- Avoid situations that are likely to evoke strong emotions, or prepare ahead of time by sitting down or having a companion nearby
- Do not drive a car or operate heavy machinery until cleared by a medical provider
- Enlist the help of significant others and friends, and educate them on the seriousness of the disorder.
Cataplexy is a transient, sudden loss of voluntary muscle control brought on by a strong emotional trigger such as laughing. Cataplexy is almost always associated with narcolepsy.
As cataplexy is easily overlooked, the average time from first symptoms to diagnosis is 7 years. There is no cure for cataplexy; however, with education, sleep hygiene practices and prescription medication, an individual suffering with this disorder can get a handle on its symptoms and enjoy a better quality of life.