New Terms Seizure Classification
The International League Against Epilepsy (ILAE) has approved a new way of organizing seizures that reflects recent advances in our understanding of the brain and seizures. This new system will make diagnosis and classification of seizures easier and more accurate.
These terms don’t change what occurs during a seizure, but offer a different way of naming seizures. More accurate ways of naming seizures can lead to more appropriate treatment.
Listen to Drs. Joe Sirven and Bob Fisher discuss the changes in a Hallway Conversations podcast:
What are the major changes in terms used to describe seizures?
Seizures will first be classified according to where they start in the brain. There are now 3 main categories:
- Generalized Onset: Generalized seizures affect both sides of the brain or large networks of cells on both sides from the beginning of the event. The networks can be on the surface of the brain or involve deeper areas. Generalized seizures don’t need to involve the entire brain, just part of both sides.
- Focal Onset: The term focal seizure has been used for years, but the lay public and many professionals still use the term partial seizures. In this 2017 Classification, focal seizures will replace partial seizures and refer to those that start in an area or network on one side of the brain. They may start on the surface of the brain or in deeper areas, and can be very localized or spread to larger areas. Sometimes more than one network is involved.
- Unknown Onset: Seizures may be of unknown onset if the beginning of the seizure is not clear. As more information becomes available over time or through testing, the type of seizure may be changed to a generalized or focal onset seizure.
Is a person’s awareness or consciousness considered in the seizure classification?
Yes, focal onset seizures can be grouped according to whether a person is aware or not aware during an event.
- Focal Aware: During a focal aware seizure, there is no change in a person’s awareness, even if they are unable to talk or respond during the event. This replaces the term simple partial seizure.
- Focal Impaired Awareness: If awareness is impaired at any time during a focal seizure, it would be called a focal impaired awareness seizure. This replaces the term complex partial seizure.
- Focal to Bilateral Tonic Clonic: A focal seizure may start in one part of the brain with the person aware or with impaired awareness. It may then spread to involve both sides of the brain and the person would be unaware during the seizure. Usually other changes occur, for example the seizure may spread to cause body stiffness (tonic) and jerking movements (clonic). The term focal to bilateral tonic clonic will now be used instead of the old term secondary generalized seizure. The term generalized is being used only to describe the onset or beginning of a seizure.
How are other symptoms of focal seizures described?
What happens during a focal seizure can be described as motor or non-motor symptoms.
- Motor seizures will have a change in muscle activity of some sort, such as jerking (clonic), stiffness (tonic), loss of muscle tone (atonic), or automatisms (repeated or automatic movements).
- Non-motor seizures can include changes in heart rate, breathing, or color (autonomic); blank stare, stop talking or stop moving (behavioral arrest): confusion, slowed thinking, or& problems talking and understanding (cognitive changes); sudden fear, dread, anxiety or even pleasure (emotional); or changes in hearing, vision, taste, or feelings of numbness, tingling, or pain (sensory).
What are the different types of generalized seizures?
Generalized seizures all affect a person’s awareness or consciousness in some way, so the terms ‘aware’ or ‘impaired awareness’ are not needed. Types of generalized seizures are classified by whether they have motor symptoms or non-motor. The following lists the new terms and whether this is different from before.
- Generalized Motor Seizures
- Tonic-clonic – No change (Years ago the term grand mal was used)
- Clonic – No change
- Tonic – No change
- Myoclonic – No change
- Myoclonic-tonic-clonic – New term
- Myoclonic-atonic – New term
- Atonic – No change
- Epileptic spasms – New term
- Generalized Non-Motor Seizures (Absence)
- Typical Absence – No change (Years ago the term petit mal was used)
- Atypical absence – No change
- Myoclonic absence – New term
- Eyelid myoclonia – New term
Are there categories for seizures with unknown onset?
Yes, even if a seizure’s onset or beginning is not known, it can be described by whether there are motor or non-motor symptoms.
- Motor seizures include tonic clonic and epileptic spasms
- Non-motor includes seizures with behavior arrest
Is there a simple way to see how old terms relate to new terms?
Most older terms can easily be linked to a newer term. Some may not however, as the new system has new terms for seizures that didn’t fit in the old classification. Here is a partial list of old terms and new terms that may apply to them.
Old Term vs New Terms for Seizures
- Absence – Generalized absence
- Atonic or drop attack – Focal or generalized atonic
- Grand mal – Generalized or unknown onset tonic clonic
- Infantile spasms – Focal, generalized, unknown onset epileptic spasms
- Myoclonic – Focal or generalized myoclonic
- Petit mal – Generalized absence
- Tonic clonic – Generalized or unknown onset tonic clonic
- Tonic or drop attack – Focal or generalized tonic
- Complex partial – Focal impaired awareness
- Focal motor – Focal motor aware or impaired awareness
- Focal sensory – Focal sensory aware or impaired awareness
- Limbic – Focal impaired awareness
- Psychomotor – Focal impaired awareness
- Simple partial – Focal aware
Reference: Fisher RS, The 2017 ILAE Seizure Classification. Presented at the American Epilepsy Society Annual Meeting, December 2016.
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