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What is a myoclonic seizure?
Myoclonic (pronounced “my-oh-CLON-ick”) seizures are a type of seizure that cause a quick, uncontrollable muscle movement with no change in your level of awareness or consciousness. These usually affect either one muscle or a group of related muscles, but can sometimes affect wider areas of your body.
This kind of seizure can happen on its own, but it also typically occurs as a symptom of another medical condition. It’s common for people with those conditions to have other kinds of seizures, too.
On their own, myoclonic seizures aren’t usually disabling. They’re also very brief, aren’t painful and are usually treatable with medication. However, they can also happen with some severe forms of epilepsy.
What is the difference between a myoclonic seizure and myoclonus?
Myoclonus (pronounced “my-OCK-lon-us”) is the term for a quick, sharp muscle movement, which often looks like a twitch or a spasm. It can affect one muscle or groups of related muscles. A myoclonic seizure is a type of myoclonus that happens because of an underlying epileptic condition in your brain. Epilepsy is a disease in which abnormal electrical signals in your brain cause impairment in your ability to function normally.
It’s important to remember that myoclonus can happen in situations that aren’t associated with any severe illness and are, in fact, fairly common. There are two forms of myoclonus that you’ve probably experienced recently. These are completely normal and aren’t the same as a myoclonic seizure. They are:
- Hypnic jerks: If you’ve ever had a sudden muscle twitch or spasm right as you were falling asleep, that was a hypnic jerk (the name comes from “hypnos,” the Greek word for “sleep”).
- Hiccups (sometimes spelled “hiccoughs”): These are a form of myoclonus that affects your diaphragm, the muscle that controls how much air your lungs hold.
Is a myoclonic seizure the same as epilepsy?
Seizures and epilepsy are closely related, but they aren’t the same thing. Everyone can have seizures under the right circumstances, but some people have conditions that make seizures happen more easily.
Your healthcare provider might use the term “seizure” when they suspect that abnormal brain signals led to the episode. So, in that situation, seizures are a symptom of epilepsy. Sometimes, though, it’s not always clear if a symptom is truly related to epilepsy. Often, healthcare providers use tests such as EEG to determine whether a person’s seizures are related to epilepsy.
- Provoked: These seizures happen because of a specific health condition. Examples of these conditions include very high fevers, low blood sugar, drug or alcohol misuse and withdrawal, etc.
- Unprovoked: These happen because of changes in your brain or medical conditions that make it easier for seizures to start.
For a person to get an epilepsy diagnosis, they need to either have at least two unprovoked seizures, or one unprovoked seizure and a high probability of having another in the next 10 years. Healthcare providers can often determine you have that risk because of certain changes in your brain’s structure or activity.
Who does it affect?
Myoclonic seizures are most common in people with generalized or genetic epilepsy. People with focal epilepsy might experience myoclonic seizures as well. With focal epilepsy, the muscle jerks only affect one side of your body.
How common are myoclonic seizures?
Myoclonic seizures are a fairly common seizure type, especially in people with juvenile myoclonic epilepsy (JME). In JME, myoclonic seizures are one of the main seizure types. JME is a common form of childhood generalized (genetic) epilepsy. JME makes up about 5% to 10% of all epilepsy cases.
How does this condition affect my body?
A seizure is when there’s a burst of uncontrolled electrical activity in your brain. With myoclonic seizures, this burst of electrical activity is very brief, so these seizures usually last only a fraction of a second.
Myoclonic seizures can affect one or both sides of your brain. One-sided seizures affect one side of your body, while seizures that affect both sides will cause more intense or severe symptoms on both sides of your body.
Symptoms and Causes
What are the symptoms of a myoclonic seizure?
Myoclonic seizures cause muscles to contract in a way that’s very sudden and that you don’t control. They can happen in one of two ways:
- Positive myoclonus: This involves muscles contracting suddenly. This looks and feels much like a muscle spasm.
- Negative myoclonus: This involves muscles suddenly losing tension when you’re using them. An example of this would be dropping something you were carrying because the muscles in your hand suddenly relaxed and you lost your grip.
They usually involve the following features or circumstances:
- They are very brief. Muscle contractions that happen with myoclonic seizures are similar to the effect of a minor electric shock (like from static buildup on fabric), which causes affected muscles to tighten up for a fraction of a second.
- They usually happen to small groups of muscles. Examples include the muscles in your arms, legs or face. If they affect larger areas, these are usually in your chest, back or belly.
- They happen in limited numbers. A myoclonic seizure usually causes muscle contractions to happen only once, but sometimes, you can have a few of these in a brief period.
- They’re more likely under certain circumstances. A common time when people have myoclonic seizures is first thing in the morning when they wake up. They can also happen when a person is very tired or hasn’t slept, when they feel stressed or anxious, or after drinking alcohol.
- You’re usually aware of them. Passing out or losing awareness of the world around you is common with many types of seizures but usually doesn’t occur with myoclonic seizures. However, you can have muscle movements that are like a myoclonic seizure while having another kind of seizure, such as an absence seizure.
What causes myoclonic seizures?
Myoclonic seizures usually occur as a result of epilepsy. This condition makes it easier for your brain cells to malfunction and start sending electrical signals uncontrollably. Many forms of epilepsy are genetic, and people who have them often inherit them from one or both parents.
The most common types of epilepsy that involve myoclonic seizures include:
- Juvenile myoclonic epilepsy. This type of epilepsy usually starts between ages 12 and 18 and also involves other kinds of seizures. These include absence seizures and tonic-clonic seizures. It’s usually an inherited condition.
- Lennox-Gastaut syndrome. This is a rare, severe form of childhood epilepsy that almost always starts before age 10. It involves several types of seizures, including myoclonic.
- Myoclonic-astatic epilepsy. This form of epilepsy causes myoclonic seizures that affect both sides of the body. After the seizure, the affected muscles go slack. The term “astatic” comes from the Greek word that means “unsteady.” It has that name because this type of epilepsy commonly causes a person with it to fall.
- Myoclonic epilepsy of infancy (MEI). This form of epilepsy usually happens before age of 3 but can start as late as age 5. Myoclonic seizures with this are more likely to happen when a child is awake than when they’re sleepy or tired. It usually goes away on its own anywhere between six months and five years after it starts.
- Progressive myoclonus epilepsy. This is a very severe type of epilepsy that worsens over time. It usually involves brain deterioration or damage that also affects memory, muscle control, thinking ability and more. Some forms of this are eventually fatal.
Myoclonic seizures can also happen with conditions or circumstances that disrupt how your brain should work. Examples of these include:
- Brain tumors (including cancer).
- Cerebral hypoxia (lack of oxygen).
- Severe concussion and traumatic brain injury.
- Degenerative brain diseases like Alzheimer’s disease or frontotemporal dementia.
- Drugs and alcohol (this includes prescription medications, recreational drugs and even caffeine).
- Drug or alcohol withdrawal.
- Infections (especially encephalitis or meningitis; infections can happen because of viruses, bacteria, parasites or fungi).
- Metabolic problems, especially high blood sugar (hyperglycemia) or low blood sugar (hypoglycemia).
- Toxic levels of metals like lithium (which treats several mental health conditions when used in prescribed amounts).
There are other types of myoclonus that aren’t myoclonic seizures, including:
- Subcortical myoclonus. Certain forms of myoclonus can occur as a result of disease or damage to areas in your nervous system that are deeper than the outer surface of your brain (cortex). This form of myoclonus is called subcortical myoclonus. The areas of your nervous system that can produce subcortical myoclonus are anywhere below the outer surface of your brain (below the cortex), brainstem, as well as your spinal cord.
- Peripheral myoclonus. This is a type of myoclonus that results from injury to your peripheral nervous system.
- Lance-Adams syndrome. This is a rare brain disease that results from complications after a period of oxygen deprivation. This usually affects people who suffered a heart attack and went into cardiopulmonary arrest. Cardiopulmonary arrest is when your heart and lungs stop working. People who survive a cardiopulmonary arrest were usually saved by having cardiopulmonary resuscitation (CPR) performed on them. People with Lance-Adams syndrome experience something called action myoclonus. These are uncontrollable muscle jerks that worsen when attempting to make any movement.
Are myoclonic seizures contagious?
Myoclonic seizures aren’t contagious, and you can’t pass them from person to person.
Diagnosis and Tests
How is a myoclonic seizure diagnosed?
A healthcare provider will usually suspect myoclonic seizures based on symptoms you describe to them (when either you have symptoms or you see symptoms in your child). Once they suspect myoclonic seizures, several different types of tests can help rule out other conditions and confirm that these seizures are happening.
What tests will be done to diagnose this condition?
The main way to diagnose myoclonic seizures is using a test called an electroencephalogram (EEG) or video-EEG. This test measures electrical activity in your brain, looking for unusual activity patterns that indicate a problem with how your brain works. A video-EEG also records the movement with video while also recording EEG.
Other tests are also possible as healthcare providers try to confirm or rule out other conditions. The possible tests (some of which may happen before an EEG) include:
- Blood tests (these look for metabolic and blood chemistry imbalances, infections and more).
- Computerized tomography (CT) scan.
- Magnetic resonance imaging (MRI).
- Spinal tap (lumbar puncture).
Management and Treatment
How are myoclonic seizures treated, and is there a cure?
Myoclonic seizures are so short-lived that sometimes, rescue medications can be prescribed to help prevent clusters of myoclonic seizures. Rescue medications usually fall under the category of various types of benzodiazepines, including Ativan®, Valium®, clonazepam, clobazam, etc. There are other medications used to treat other types of epileptic seizures, which can also be used to control myoclonic seizures. Some people may need only one medication to prevent their seizures, while others might need a combination of medications. Your healthcare provider is the best person to explain your options and help you find what works best for you.
However, some of the more severe conditions may not respond to medication, and these may need other forms of treatment, such as:
- Epilepsy surgery.
- Diet changes, such as low- or no-carb (ketogenic) diets.
- Implantable devices for vagal nerve stimulation, responsive neurostimulation or deep brain stimulation.
Complications/side effects of the treatment
Because there are many different medications (and combinations of those medications) that can treat conditions that cause myoclonic seizures, the possible side effects and complications can vary. Your healthcare provider is the best person to tell you about medications and their side effects.
How to take care of myself/manage symptoms?
Myoclonic seizures are muscle jerks that happen because of seizure activity in your brain. Myoclonus can also happen with many other conditions, some of which are dangerous or even deadly. Because of that, you should see a trained, qualified healthcare provider who can diagnose and treat this condition.
How soon after treatment will I feel better?
Your recovery time and how long it takes you to feel better after starting treatment can vary. Your healthcare provider is the best person to tell you what you can expect and what you can do to help yourself as you recover.
How can I prevent myoclonic seizures or reduce my risk of having them?
Seizures can happen to anyone under the right circumstances, so it’s impossible to prevent them completely. However, there are things you can do that will reduce your risk of seizures or the conditions that cause them, including:
- Don’t abuse alcohol, prescription or recreational drugs. Abusing these can lead to seizures, and withdrawal from these substances can also lead to seizures if you’re dependent on them.
- Manage your health conditions. Managing chronic conditions can help you avoid seizures, especially those that happen because of your blood sugar with either Type 1 diabetes or Type 2 diabetes. Treating hypertension, controlling your cholesterol level and avoiding smoking can decrease your risks for strokes and heart attacks. These conditions can damage your brain and lead to various forms of myoclonus, including myoclonic seizures.
- Don’t ignore infections. Eye and ear infections are especially important to treat. If these infections spread to your brain, they can cause seizures. Infections can also cause high fevers, which can lead to seizures.
- Wear safety equipment. Head injuries are a major cause of seizures. Using safety equipment (helmets, safety belts and restraints, etc.) can help you avoid an injury that leads to a seizure.
- Avoid possible seizure triggers. People with a history of seizures from flashing lights should use caution and avoid similar triggers whenever possible. You should also be careful drinking alcohol (or avoid it altogether if your healthcare provider advises that).
Outlook / Prognosis
What can I expect if I have myoclonic seizures?
Myoclonic seizures usually aren’t severe or painful. They aren’t dangerous on their own, and medication is usually all it takes to treat them or the conditions that cause them.
However, myoclonic seizures can be a warning sign when you have a condition that also causes other kinds of seizures. Many people with these conditions will have myoclonic seizures hours or even days ahead of a much larger, more severe tonic-clonic seizure. Your healthcare provider can help determine if myoclonic seizures are a warning sign of bigger seizures and what, if anything, you can do to use this information to your advantage.
How long do myoclonic seizures last?
Myoclonic seizures are very short-lived. Most only last a fraction of a second, or they happen in clusters where you have a few of them in a short period.
Many of the conditions that cause myoclonic seizures start during childhood. Children can grow out of these by the time they become adults. Your healthcare provider can help determine if this is likely to happen for your child. They’ll also help determine the best way to reduce and then stop your child’s medication safely.
When a person doesn’t grow out of these conditions or develops them as an adult, myoclonic seizures can be a lifelong concern. With treatment, some people can control myoclonic seizures entirely. In some people who have myoclonus as a result of focal epilepsy, epilepsy surgery can sometimes eliminate myoclonic seizures. However, there’s no way to predict if a person will outgrow myoclonic seizures once they’ve developed the condition. Because of that, experts consider a person who is seizure-free for an extended period “in remission” from these conditions.
What’s the outlook for this condition?
Myoclonic seizures on their own aren’t dangerous, and they don't cause severe side effects like brain damage or problems with thinking, concentration or memory. However, myoclonic seizures can happen with conditions that cause dangerous seizures and complications, so it’s important to see your healthcare provider for diagnosis and treatment as early as possible.
How do I take care of myself?
If you have myoclonic seizures or a condition that causes them, your healthcare provider will give you guidance, information and resources that can help you manage this condition. It’s important to follow that guidance closely and ask questions if you don’t understand. If your treatments aren’t as effective as you’d like or you experience problems from side effects, talk to your healthcare provider about these concerns. They can often help you find other treatments that work better or minimize side effects.
Other important things you can do include:
- Take medications as prescribed, and don’t stop taking them without first talking to your healthcare provider.
- Don’t ignore or avoid new symptoms or changes in symptoms you already have.
- Avoid seizure triggers (such as flashing lights, alcohol, sleep deprivation, etc.).
When should I see my healthcare provider, or when should I seek care?
You should see your healthcare provider as recommended for follow-up visits. You should also see them if you notice any changes in how well your medication works, any new symptoms or issues you’re experiencing, or if the side effects disrupt your activities and routine.
When should I go to the ER?
You should go to the emergency room if you pass out unexpectedly for an unknown reason. This is rare with myoclonic seizures, but it’s possible when you have a condition that causes other kinds of seizures, too.
Calling an ambulance after a seizure is often unnecessary if someone is known to have epilepsy, unless the seizure is persisting past 2 minutes, if they aren’t returning to their baseline or if they’ve suffered injuries from their seizure. Myoclonic seizures can cause you to fall or injure yourself, so it’s important to get medical care if you have injuries after this kind of seizure.
A note from Cleveland Clinic
Myoclonic seizures are a relatively common type of seizure that cause uncontrollable, lightning-fast muscle movements. While these seizures in isolation aren’t usually dangerous or harmful, they can cause problems when you lose control of muscles during activities, such as walking or carrying something. They can also be a warning sign that a more severe seizure is imminent. They’re more common with epilepsy disorders that affect children, but can also happen in adults. Fortunately, myoclonic seizures are usually manageable with medication to reduce how often they happen or prevent them for extended periods.
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