2017 Revised Classification of Seizures

The International League against Epilepsy (ILAE) is the world's main scientific body devoted to the study of epilepsy, and it has recently revised its classification of seizures. The changes will help make diagnosing and classifying seizures more accurate and easier. In this article, you'll find the new general outline and basic seizure classification. In the coming weeks, epilepsy.com will be updated to reflect the new classification to help users searching for both the older and newer terms.

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  • Atonic means a loss of muscle tone. In an atonic seizure, a person suddenly loses muscle tone so their head or body may go limp.
  • They are also known as drop attacks.
  • In some children, only their head drops suddenly.
  • Atonic seizures can be begin in one area or side of the brain (focal onset) or both sides of the brain (generalized onset).

What is an atonic seizure?

Muscle "tone" is the muscle's normal tension. "Atonic" (a-TON-ik) means "without tone." So in an atonic seizure, muscles suddenly become limp.

  • Part of all of the body may become limp. The eyelids may droop, the head may nod or drop forward, and the person may drop things.
  • If standing, the person often falls to the ground.
  • These seizures typically last less than 15 seconds.
  • People may get injured when they fall. Head protection, such as a helmet or other protective gear, may be needed.
  • These seizures are also called "drop attacks" or "drop seizures."

What part of the brain is involved?

When the seizure starts in one area of the brain:

  • Atonic seizures can start in one part of the brain with a loss of tone in one part of the body.
  • This is called a focal motor atonic seizure.

When the seizure starts on both sides of the brain:

  • Usually, atonic seizures affect both sides of the brain.
  • These are called generalized onset atonic seizures.
  • These seizures would begin with a sudden drop or loss of tone affecting the head, trunk, or whole body.
  • Usually a person having a generalized atonic seizure is not fully aware during the event.

Who is at risk for atonic seizures?

  • Atonic seizures usually begin in childhood and may last into adult years.
  • Often these seizures may be seen in syndromes like Lennox-Gastaut or Dravet syndrome. Other types of seizures may occur in the same person too.

What’s it like to have an atonic seizure?

In an atonic seizure, the person's body will suddenly become limp.

  • If sitting, their head or upper body may slump over.
  • If standing, the person many fall limply to the ground. Since the muscles are weak or limp, the person falls like a rag doll.
  • When a person’s muscles are stiff or rigid, they will fall like a tree trunk. These are usually called tonic seizures.

What happens after the seizure?

  • After an atonic seizure, the person may or may not be confused.
  • Often a person can return to their usual activity fairly quickly. Some may need to rest for a while after a seizure.
  • If the person fell, they may have been injured and need first aid for bruises, cuts, or other injuries.
  • For serious injuries (like a broken bone or head injury), the person will need to go to an emergency room.

How often do atonic seizures occur?

It depends. People can have just one atonic seizure or several in a row. When an atonic seizure happens, try your best to make sure the person is in a safe place to prevent injuries and falls.

In some types of epilepsy (like Lennox-Gastaut or Dravet syndrome), seizures can happen in clusters with two or more at one time or in one day. If a person is at risk for seizure clusters, they should talk to their doctor or nurse about ways to treat clusters.

How are these seizures diagnosed?

  • Written descriptions or video recordings by observers of what happened are very important in diagnosing atonic seizures.
  • Sometimes EEG (electroencephalogram) monitoring may also be done to sort out the diagnosis.
  • If the diagnosis is not clear or seizures don’t stop with medications, other tests may be done. The testing would check for changes in the heart rhythm, blood pressure, or other problems that could cause falls.

How are atonic seizures treated?

What should I do if I think my child or loved one may have atonic seizures?

If you think your loved one or you may be having atonic seizures, it is important to talk to your health care provider right away. These seizures have the potential to cause serious injury due to falls. Getting a correct diagnosis and proper treatment is important.

Authored by: Elaine Kiriakopoulos MD | Patricia O. Shafer RN, MN | Joan Sirven | Orrin Devinsky MD on 3/2017
Reviewed by: Robert Fisher MD, PhD | Joseph I. Sirven MD on 3/2017
What It Looks Like...

When Bob has a 'drop' seizure, he falls to the ground and often hits his head and bruises his body. Even if I'm right next to him and prepared, I may not catch him. Even with carpet in the bedroom and mats in the bathroom, he gets hurt.