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Seizure classification

There are many different types of epileptic seizure. Seizure classification is a way of naming different types of epileptic seizures and putting them into groups. It’s important for healthcare professionals to all use the same names for seizures to avoid confusion. Being able to recognise and name a seizure accurately is also important, because some medicines and treatments can help some seizure types but not others.

How has seizure classification changed?

The International League Against Epilepsy (ILAE) is a world-wide organisation of epilepsy professionals. In 2017 they announced a different way of organising and naming seizures. Many of the names for seizures are the same as before. But the ILAE has also introduced some new names for seizures, for example focal aware instead of simple partial. The new names don’t change what happens during seizures, but they do give doctors a more accurate way to describe them.

How does the new seizure classification work?

To name a seizure using the new classification, doctors look at 3 things:

  1. Where in your brain the seizure starts
  2. Your level of awareness during the seizure
  3. Whether the seizure involves movement or not

 1.    Where the seizure starts (the onset)

Seizures can be either focal onset, generalised onset, or unknown onset.

Focal onset

Focal onset means the seizure starts in just one side of the brain. These seizures used to be called partial seizures. Sometimes, a seizure can start as a focal seizure and then spread to involve both sides of the brain. When this happens, it’s called a focal to bilateral tonic-clonic seizure.

Generalised onset

Generalised onset means the seizure affects both sides of the brain from the start.

Unknown onset

Unknown onset means the beginning of the seizure is not clear. As doctors get more information about the seizure, they may be able to decide if it is focal or generalised in onset.

Rarely, doctors might be sure that someone has had an epileptic seizure, but can’t decide what type of seizure it is. This could be because they don’t have enough information about the seizure, or the symptoms of the seizure are unusual. When this happens, it’s called an unclassified seizure.

2.    The level of awareness

Focal onset seizures can be put into one of 2 groups depending on what level of awareness you have during the seizure.

Focal aware

During a focal aware seizure, you stay fully aware of what’s happening around you, even if you can’t talk or respond. These seizures used to be called simple partial seizures.

Focal impaired awareness

If your awareness is affected at any time during a focal seizure, it’s called a focal impaired awareness seizure. This replaces the term complex partial seizure.

Generalised onset seizures almost always affect your awareness in some way, so the terms ‘aware’ or ‘impaired awareness’ aren’t used for them.

3.    Whether the seizure involves movement or not

Seizures can also be split into motor seizures, which means they involve movement, or non-motor seizures, which means they don’t involve movement.

Motor seizures

A motor seizure is any seizure that involves a change in your movement. For example, a tonic-clonic seizure – where all your muscles go stiff before making rhythmic jerking movements – is a type of motor seizure.

Focal seizures can also be motor seizures if the main symptom involves movement, for example automatic behaviour like plucking at clothes or repeated swallowing.

Non-motor seizures

A non-motor seizure is any seizure that doesn’t involve changes in movement. A focal seizure where your main symptom is a change in vision, smell or hearing is a type of non-motor seizure. Absence seizures are also non-motor seizures.

See this information with references

If you would like to see this information with references, visit the Advice and Information references section of our website. If you are unable to access the internet, please contact our Epilepsy Helpline by email at helpline@epilepsy.org.uk

Code: 
B037.04

Epilepsy Action would like to thank Professor Helen Cross, The Prince of Wales’s Chair of Childhood Epilepsy and Honorary Consultant in Paediatric Neurology at UCL Institute of Child Health and Great Ormond Street Hospital for Children, for her contribution to this information.

Professor Cross has declared no conflict of interest.

This information has been produced under the terms of The Information Standard.

  • Updated July 2017
    To be reviewed July 2020

Comments: read the 1 comments or add yours

Comments

Whilst the new classification is understandable for those with a good knowledge of epileptic seizures it may well confuse those who have for example been diagnosed with for example temporal lobe epilepsy. Also much training resources exist based on the former ILAE definitions

Submitted by Roger Kendall on