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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ILAE 2017 classification of seizure types basic version
  • Seizures are generally described in two major groups of seizures: generalized seizures and focal seizures.
  • The difference between the types of seizures is in how and where they begin in the brain.

There are many different types of seizures.

New terms to describe and classify seizures have been developed by the International League Against Epilepsy. This was done to make the names of seizures more accurate, less confusing, and more descriptive of what is happening.

Listen to Drs. Joe Sirven and Bob Fisher discuss the changes in a Hallway Conversations podcast:

The new terms consider these important areas when describing seizures.

  1. The onset or beginning of a seizure: Where seizures start in the brain tells a lot about what may occur during a seizure, what other conditions or symptoms may be seen, how they may affect someone and, most importantly, what treatment may be best for that seizure type. When we don’t know the onset of a seizure, the wrong treatment may be used. Or a person may not be offered a treatment that has the best chance of helping.
  2. A person’s level of awareness during a seizure: Whether a person is aware or not tells a lot about the type of seizure. It’s also very important to know for a person’s safety.
  3. Whether movements happen during a seizure: Seizures can also be described by whether motor symptoms occur. When no motor symptoms happen, it can be called a non-motor seizure. This level of description does not need to be used all the time, especially when generally describing or talking about seizures. Yet other times you may find the motor terms helpful.

How are seizures classified now?

There are now 3 major groups of seizures.

  1. Generalized onset seizures: These seizures affect both sides of the brain or groups of cells on both sides of the brain at the same time. This term was used before and still includes seizures types like tonic-clonic, absence, or atonic to name a few.
  2. Focal onset seizures: The term focal is used instead of partial to be more accurate when talking about where seizures begin. Focal seizures can start in one area or group of cells in one side of the brain.
    • Focal Onset Aware Seizures: When a person is awake and aware during a seizure, it’s called a focal aware seizure. This used to be called a simple partial seizure.
    • Focal Onset Impaired Awareness: When a person is confused or their awareness is affected in some way during a focal seizure, it’s called a focal impaired awareness seizure. This used to be called a complex partial seizure.
  3. Unknown onset seizures: When the beginning of a seizure is not known, it’s now called an unknown onset seizure. A seizure could also be called an unknown onset if it’s not witnessed or seen by anyone, for example when seizures happen at night or in a person who lives alone.
    • As more information is learned, an unknown onset seizure may later be diagnosed as a focal or generalized seizure.

How are different symptoms during a seizure described?

Many different symptoms happen during a seizure. This new classification separates them simply into groups that involve movement.

For generalized onset seizures:

  • Motor symptoms may include sustained rhythmical jerking movements (clonic), muscles becoming weak or limp (atonic), muscles becoming tense or rigid (tonic), brief muscle twitching (myoclonus), or epileptic spasms (body flexes and extends repeatedly).
  • Non-motor symptoms are usually called absence seizures. These can be typical or atypical absence seizures (staring spells). Absence seizures can also have brief twitches (myoclonus) that can affect a specific part of the body or just the eyelids.

For focal onset seizures:

  • Motor symptoms may also include jerking (clonic), muscles becoming limp or weak (atonic), tense or rigid muscles (tonic), brief muscle twitching (myoclonus), or epileptic spasms. There may also be automatisms or repeated automatic movements, like clapping or rubbing of hands, lipsmacking or chewing, or running.
  • Non-motor symptoms: Examples of symptoms that don’t affect movement could be changes in sensation, emotions, thinking or cognition, autonomic functions (such as gastrointestinal sensations, waves of heat or cold, goosebumps, heart racing, etc.), or lack of movement (called behavior arrest).

For unknown onset seizures:

  • Motor seizures are described as either tonic-clonic or epileptic spasms.
  • Non-motor seizures usually include a behavior arrest. This means that movement stops – the person may just stare and not make any other movements.

What if I don’t know what type of seizures I or my loved one have?

It’s not unusual that a person doesn’t know the type of seizure they have. Often seizures are diagnosed based on descriptions of what an observer has seen. These descriptions may not be fully complete or one can’t tell where a seizure begins from this information.

When seizures are difficult to diagnose or seizure medicines are not working to stop seizures, talk to your doctor or treating health care provider.

How can I learn more?

Authored by: Elaine Kiriakopoulos MD | Patricia O. Shafer RN, MN on 3/2017
Reviewed by: Robert Fisher MD, PhD | Joseph I. Sirven MD on 3/2017