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It is sudden and uncontrollable muscle weakness or paralysis.
It occurs during the day and is often triggered by strong emotions, such as excitement or laughter.
Without warning, the person loses muscle tone and may have a loose jaw, broken speech, bent knees, or total weakness in the face, arms, legs, and trunk.
A person experiencing total cataplexy remains awake and aware of what is happening but cannot move.
These episodes last up to a minute or two, and some people may fall asleep afterward.
The frequency of cataplexy episodes varies widely among people with narcolepsy. Some people avoid emotions that can cause cataplexy.
Loss of muscle tone in cataplexy occurs due to the inability to regulate sleep and waking states, which means that the elements of each can overlap.
There is a natural loss of muscle tone during normal rapid eye movement (REM) sleep.
In the case of cataplexy, this feature of REM sleep occurs suddenly during the day, causing weakness or total paralysis, even when the person remains awake during the episode.
Causes of cataplexy
The REM sleep dissociation hypothesis suggests that cataplexy is muscle paralysis that usually occurs during REM sleep and waking hours.
The exact underlying cause of this intrusion is unknown, but the loss of hypocretin-producing neurons (also known as orexin) is believed to be a significant contributing factor.
Hypocretin is a neurotransmitter involved in promoting wakefulness within the sleep/wake cycle.
People with cataplexy have been found to have a specific human leukocyte antigen, variations in T-cell receptors, or dysfunctional immune system responses to particular antigen exposures.
Narcolepsy is believed to be an autoimmune disorder, but more research is needed.
A study published in 2010 revealed that hypocretin loss is caused by an autoimmune response directed at homologous tribble 2 (trib 2) autoantibodies.
This autoimmune response causes two antibodies to form, which attack and kill neurons in the brain that produce hypocretin.
Cataplexy episodes range from less than one per year to several per day. A person with cataplexy will experience one or more episodes each week.
Symptoms
Symptoms of cataplexy associated with narcolepsy often begin in childhood and early adulthood, between the ages of 7 and 25, but can start.
Cataplegic attacks can vary widely. They can be mild and barely noticeable or severe with total body collapse.
Symptoms of a cataplectic episode can include:
- Shaky knee or buckling.
- Fallen eyelid.
- Speech difficulty
- A person can collapse and be unable to move.
An individual experiencing cataplexy remains conscious, can breathe, and move the eyes.
Diagnosis of cataplexy
The tests can help diagnose narcolepsy with cataplexy, but the diagnosis is also based on the patient’s description of the events and history.
Often a person complains to a doctor about excessive daytime sleepiness (EDS) with a persistent feeling of drowsiness during waking hours. EDS is commonly the first symptom of narcolepsy.
However, if cataplexy occurs with EDS, narcolepsy is likely to present.
People who have EDS or cataplexy symptoms should see their healthcare provider.
The provider will most likely order a sleep study (a polysomnogram), followed by a multiple sleep latency test (MSLT) and five scheduled naps for the day.
They perform the MSLT the day after the polysomnography allows clinicians to determine whether the night’s sleep affected the daytime nap.
Treatment and prevention of cataplexy
There is no cure for cataplexy, and treatment is managing symptoms with good sleep hygiene practices and using medications as needed.
In addition, safety measures must be implemented to prevent serious injuries resulting from falls.
Good sleep hygiene practices include:
- Maintain a consistent sleep schedule, including getting up and going to bed simultaneously every day, even on weekends or during vacations.
- Get at least 7 to 8 hours of sleep, or the amount that usually makes you feel refreshed.
- Keep the room calm and relaxing and keep it at a comfortable and relaxed temperature.
- Limit exposure to light at night.
- I was exercising regularly and maintaining a healthy diet.
- Avoid a large meal before bed and opt for a light, healthy snack if necessary.
- Avoid caffeine in the afternoon or evening.
- Avoid alcohol.
- Schedule one or more short naps during the day.
Medicines
Sodium oxybate at doses between 6 and 9 grams (g) at night is the drug approved by the Food and Drug Administration (FDA) to treat cataplexy. Sodium oxybate is effective in reducing both the frequency and intensity of attacks.
Possible side effects are:
- Dizziness
- Headache.
- Sickness.
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 and other significant CNS depressant effects.
Other medications that can help control symptoms are antidepressants. These include venlafaxine, a serotonin-norepinephrine reuptake inhibitor (SNRI) antidepressant, and tricyclic antidepressants such as clomipramine, imipramine, and desipramine.
However, the evidence supporting the use of antidepressants for cataplexy is mixed. Also, abrupt withdrawal from venlafaxine can cause rebound cataplexy.
Regarding safety, even if an individual detects the onset of an episode, an injury with cataplexy is highly possible.
An injury can occur if a person falls suddenly. To help prevent cataplexy injury from occurring:
- Assess and consider potential hazards, such as glass, sharp edges, and heights.
- Practice relaxation and stress management techniques.
- Avoid sleep deprivation.
- Avoid situations that can 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 authorized by a medical provider.
- Enlist the help of important people and friends and teach them the severity of the disorder.
Cataplexy is a sudden, temporary loss of voluntary muscle control caused by a strong emotional trigger, such as laughter or excitement. Cataplexy is almost always associated with narcolepsy.
