Seizure Types & Classification
There are many different types of seizures. In recent times there have been major technological and scientific advances that have dramatically changed our understanding of epilepsy. As a result, there have been recent changes made to seizure terminology.
As it takes time to adopt changes, you may encounter clinicians, websites and materials that use the previous terminology. To help with this change we have placed the previous term in brackets next to the newer terminology.
Seizures can be divided into three major groups: focal (partial), generalised and unknown.
1) Focal (partial) seizures
About 60% of people with epilepsy have focal (partial) seizures. These seizures can often be subtle or unusual, and may go unnoticed or be mistaken for anything from intoxication to daydreaming. Seizure activity starts in one area of the brain and may spread to other regions of the brain.
Types of focal (partial) seizures are:
- Focal seizure - awareness retained (formerly simple partial seizures)
- Focal dyscognitive seizures - awareness altered (formerly complex partial seizures)
Focal seizures evolving to a bilateral convulsive seizure (formerly secondarily generalised Tonic-Clonic*) *see note below.
2) Generalised seizures
Generalised seizures are the result of abnormal activity in both hemispheres of the brain simultaneously. Because of this, consciousness is lost at the onset of the seizure.
There are many types of generalised seizures:
- Atypical absence
- Absence with special features
- Myoclonic absence
- Eyelid Myoclonia
- Myoclonic atonic
- Myoclonic tonic
This is a grouping of seizures that can not be diagnosed as either a focal or generalised seizure and are thus grouped as unknown.
- Epileptic spasms
*Note: Sometimes a seizure starts as a focal (partial) seizure and then becomes a generalised seizure - almost always a tonic-clonic seizure.
Most people will only have one or two seizure type(s), which may vary in severity. A person with severe epilepsy or significant damage to the brain may experience several different seizure types.
Here is a simple diagram showing how seizures are classified: