What is a tonic-clonic seizure?

This type of seizure (also called a convulsion) is what most people think of when they hear the word "seizure." An older term for this type of seizure is "grand mal." As implied by the name, they combine the characteristics of tonic and clonic seizures. Tonic means stiffening, and clonic means rhythmical jerking.

  • The tonic phase comes first.
    • All the muscles stiffen.
    • Air being forced past the vocal cords causes a cry or groan.
    • The person loses consciousness and falls to the floor.
    • A person may bite their tongue or inside of their cheek. If this happens, saliva may look a bit bloody.
  • After the tonic phase comes the clonic phase.
    • The arms and usually the legs begin to jerk rapidly and rhythmically, bending and relaxing at the elbows, hips, and knees.
    • After a few minutes, the jerking slows and stops.
  • The person’s face may look dusky or a bit blue if they are having trouble breathing or the seizure lasts too long.
  • The person may lose control of their bladder or bowel as the body relaxes.
  • Consciousness, or a person’s awareness, returns slowly.
  • These seizures generally last 1 to 3 minutes. Afterwards, the person may be sleepy, confused, irritable, or depressed.
  • A tonic-clonic seizure that lasts longer than 5 minutes needs immediate medical help. Call 911 for emergency help.
  • A seizure that lasts more than 5 minutes, or three seizures in a row without the person coming to between them, is a dangerous condition. This is called status epilepticus; emergency treatment in a hospital is needed.

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What part of the brain do tonic-clonic seizures come from?

Tonic-clonic seizures can start in one or both sides of the brain.

  • When they start in both sides of the brain, they are called generalized onset motor seizures or a generalized tonic-clonic seizure. Both terms mean the same thing.
  • When they start in one side of the brain and spread to affect both sides, the term focal to bilateral tonic-clonic seizure is used.

Who is at risk for tonic-clonic seizures?

This type of seizure can affect both children and adults.

  • When tonic-clonic seizures happen in childhood, some children will outgrow their epilepsy. Others who are seizure-free for a year or two while taking seizure medicine may be able to come off medicine slowly. Decisions about coming off medicine must be done with advice from a doctor.
  • The risk that a person will have more seizures depends a number of things such as whether epilepsy waves or patterns are seen on the EEG (electroencephalogram) or whether the neurological exam is normal.
    • Children who have had tonic-clonic seizures and have a normal EEG and neurological exam have a 70% chance of being seizure-free without medication.
    • If a child who has had tonic-clonic seizures has epilepsy waves on the EEG or an abnormal exam, the chance of being seizure-free off medicine is only 30%.
    • Children who have generalized onset tonic-clonic seizures are more likely to come off seizure medicine and do well than are children with tonic-clonic seizures that begin in one side of the brain (focal to bilateral).
  • Some people have types of epilepsy that include tonic-clonic seizures and other seizure types. For example, a person could also have other forms of generalized seizures (such as absence, atonic, clonic, myoclonic, or tonic) or focal onset seizures.
  • Talk to your health care providers about the different seizure types, including first aid and what to expect.

What’s it like to have a tonic-clonic seizure?

  • When people have tonic-clonic seizures, they are not aware of what’s happening.
  • First aid should be focused on making sure the person’s breathing is okay and they don’t injure themselves.
  • As the seizure ends, the person may be sleepy or confused for several minutes, an hour, or more.
  • They may lose bladder or bowel control during or after the seizure and need to go to the bathroom.
  • Sometimes, people bite their tongue or inside of the cheek during a seizure and their muscles may feel sore.
  • If any injury has happened or the seizure lasts 5 minutes or more, call for medical help.

How can I tell if someone is having a tonic-clonic seizure?

  • Some nonepileptic (psychogenic) seizures may look like tonic-clonic seizures. Often the best way to tell if an event is a tonic-clonic seizure is with video EEG monitoring. This may be recommended by your health care team if they aren’t sure of the diagnosis or how to treat your seizures.
  • Sometimes, a person may have both tonic-clonic and nonepileptic seizures. People who faint sometimes develop tonic or clonic movements. These movements are rarely as intense or prolonged as a tonic-clonic seizure.

How are tonic-clonic seizures diagnosed?

The typical appearance of a tonic-clonic seizure is usually easy to recognize.

  • A cell phone video or written description of what happens is very helpful for the doctor to know if this could be a seizure.
  • An EEG and other tests may help confirm the diagnosis or suggest a cause.

How are tonic-clonic seizures treated?

  • The main way of treating seizures is by taking medicines daily. You and your doctor can choose the best medicine once the diagnosis is clear. Sometimes it takes a while to find the right medicine for each person.
  • There are also special medicines used only when a person has more seizures than usual or to help stop further tonic-clonic seizures from occurring after it is taken. These are called rescue medicines. If your doctor prescribes one for you, make sure you have specific instructions on when to take it.
  • A special diet for epilepsy may also help control seizures in children and adults with epilepsy.
  • Devices (such as vagus nerve stimulator or responsive neurostimulator) are also available to help treat seizures that don’t respond to seizure medicine.

What should I do if I think my child, loved one, or myself may have tonic-clonic seizures?

If you think your child, loved one, or yourself may be having tonic-clonic seizures, please talk to the doctor soon as possible. Tonic-clonic seizures can lead to injury and in some rare cases death. Getting these diagnosed and treated quickly is essential.

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Authored By: 
Elaine Kiriakopoulos MD, MSc
Patty Osborne Shafer RN, MN
Authored Date: 
Reviewed By: 
Robert Fisher MD, PhD
Joseph I. Sirven MD
Wednesday, March 15, 2017