Clonic seizures cause rhythmic jerking and twitching of your muscles. They are most common in babies but can happen to anyone.

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A seizure is a sudden burst of electrical activity in your brain that can cause involuntary (uncontrollable) movements, changes in your consciousness, and other symptoms.

A clonic seizure specifically is characterized by rhythmic muscle twitching and jerking. Most clonic seizures last less than 1 or 2 minutes.

Clonic seizures can affect one or both sides of your brain and body. According to the Epilepsy Foundation, clonic seizures most often occur in babies.

Read on to learn more about clonic seizures, including how they’re different from other types of seizures, how they’re diagnosed, and treatment options.

Seizures are divided into more than 60 categories based on factors such as where in your brain they develop and whether you lose consciousness.

Clonic seizures cause your muscles to jerk and twitch rapidly. During a clonic seizure, you may be unable to control your movements. You may fall to the floor if you’re standing when a clonic seizure begins.

Clonic seizures can be subcategorized into several types, depending on where in the brain they develop:

  • Focal clonic seizures start in one region of your brain.
  • Multifocal clonic seizures start in multiple regions of your brain.
  • Generalized clonic seizures involve both sides of your brain.

Clonic seizures are further divided into categories based on your state of consciousness. During a focal clonic seizure, you may retain awareness of your surroundings. During a generalized clonic seizure, you may lose awareness or consciousness.

Tonic-clonic seizures were formerly called grand mal seizures. They have features of both clonic and tonic seizures. The word “tonic” refers to the tone or stiffness of your muscles. Tonic seizures cause sudden stiffness in your muscles.

Tonic-clonic seizures have two phases: tonic and clonic. These phases are brief, and you may cycle back and forth between them several times during a single seizure episode.

The tonic phase occurs first. During this phase, you experience sudden muscle stiffness. You may fall to the ground if you’re standing. You may also drool, moan, or cry out involuntarily.

The clonic phase can begin within seconds of the first tonic movements. During this phase, you may have convulsions and jerking movements of your arms and legs. Some people also lose bladder or bowel control.

A clonic seizure can cause a repetitive jerking movement of any part of your body, including your:

  • face
  • arms
  • legs
  • diaphragm
  • throat
  • trunk

Focal clonic seizures cause symptoms on only one side of your body, while generalized seizures cause symptoms on both sides.

Babies are generally not clearly unconscious during focal clonic seizures. Their movements can look more like jitteriness. Clonic seizure movements are uncontrollable and can’t be stopped.

You may stay conscious during focal clonic seizures, but generalized seizures usually cause loss of consciousness.

How to help someone having a clonic seizure

Clonic seizures tend to be brief. It’s important not to restrain somebody’s movement while they’re having a seizure. You can protect them from falling by easing them to the ground.

Other ways you can help somebody having a seizure include the following, suggested by the Centers for Disease Control and Prevention (CDC):

  • staying with the person until the seizure is over
  • speaking calmly and trying to comfort them
  • checking for a medical bracelet
  • keeping other people around them calm
  • offering to help them get home safely afterward
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The period directly after a seizure is known as the postictal period. During this period, you may:

  • feel sleepy
  • have difficulty speaking or seeing
  • have a headache

You may retain consciousness throughout your seizure if you have a focal onset seizure. But you may not remember what happened during your seizure.

Newborns may exhibit unusual behaviors after their seizure, such as lip-smacking, crying, or laughing.

Seizures are caused by atypical electrical impulses in your brain. Which part of your brain this electrical activity occurs in is what determines your symptoms and type of seizure.

Any condition that causes changes to your brain can lead to seizures. In a case study from 2020, researchers reported a 78-year-old man who developed clonic seizures after a head injury.

Other causes of seizures include:

Epilepsy is when you have recurrent seizures that don’t have another known cause.

It’s important to see your doctor if you think you or your child is having seizures. Your doctor will review your medical history and ask you about your symptoms. Bringing a video or notes describing what happens during the seizures is helpful.

Your doctor may perform a neurological exam to assess how well your brain and spinal cord are functioning. They will also likely refer you to a specialist called a neurologist.

Neurologists can test your:

  • reflexes
  • muscles and senses
  • coordination and ability to walk
  • mental ability and memory

They’ll also likely order an electroencephalogram (EEG). An EEG involves putting sensors on your scalp to look for atypical brain activity associated with seizures. Clonic seizures are the type of seizure most consistently associated with atypical EEG results.

Your neurologist may also order brain imaging scans to look for structural changes in your brain. You may receive a CT scan or MRI scan.

Seizures are primarily treated with antiseizure medications. These medications help reduce how often your symptoms occur and how severe they are.

Many different antiseizure medications are used to treat seizures. You may have to try several different combinations before you find one that works for you. Some of the most common medications include:

If medications alone don’t reduce your symptoms, your doctor may recommend other treatments, such as:

Some people notice their seizures occur after certain triggers. Avoiding your triggers may help you reduce your seizure frequency. Some of the most common triggers include:

  • not getting enough sleep
  • experiencing stress
  • consuming alcohol
  • not taking medication

Learn more about seizure triggers.

Clonic seizures can cause jerking movements in any part of your body. Depending on where in your brain they develop, they may affect one or both sides of your body.

Clonic seizures generally last fewer than 2 minutes. Antiseizure medications may help reduce your symptoms or how long your seizures last.