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What is a tonic seizure?

Muscle "tone" is the muscle's normal tension at rest. In a tonic seizure, the tone is greatly increased: the body, arms, or legs become suddenly stiff or tense.

  • A person may be aware or have only a small change in awareness during a tonic seizure.
  • They usually happen during sleep and usually involve all or most of the brain, affecting both sides of the body.
  • They are short, usually less than 20 seconds.
  • A person may fall if standing when a tonic seizure starts.

Where does a tonic seizure start in the brain?

When it starts in one area of the brain:

Stiffening of a part of the body may begin in one area and stay local. These are called focal tonic seizures.

When it starts on both sides of the brain:

The whole body or both sides of the body may become stiff or tense from the beginning. These are called generalized tonic seizures.

Who is at risk for tonic seizures?

How can I tell if someone is having one?

  • Stiffening or other movements can be seen in other neurological problems, especially in children.
  • A written description or video of what happens during the seizure is very important. For example, tonic seizures start suddenly with forceful movements. Events that start more slowly may be due to another condition.

What happens after a tonic seizure?

  • When a tonic seizure ends, the person may or may not be sleepy or confused.
  • Typically, no first aid is needed unless a person is not fully aware during or after the seizure.
  • Preventing injury is a key part of first aid for tonic seizures. Some people may need to wear protective equipment like a helmet to prevent head injuries from falls.

If someone has tonic seizures, how often will they happen?

It depends and varies between people. Some people may have just one seizure and others may have tonic seizures that occur often or in clusters of many a day.

How are tonic seizures diagnosed?

How are tonic seizures treated?

  • Seizure medicines are the main way of treating and preventing tonic seizures.
  • If seizures are not controlled with medications, other options may be possible, such as dietary therapies, devices, or even surgery.
  • Knowing where a seizure starts and what part of the brain is involved helps you learn what options may be possible.

If seizures are not controlled, seek out the help of an epilepsy specialist or visit an epilepsy center to explore treatment options.

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

If you think that you or your loved one may be having tonic seizures, talk to your doctor as soon as possible. Getting the correct diagnosis early can help lead to better treatment.

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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
Monday, March 27, 2017