Types of seizure - overview
Back in 1989 (over 30 years ago!) there used to be only a few names for seizures - such as grand-mal and petit-mal - because so little was known about the human brain.
Due to major scientific advances since 1989, our understanding of the epilepsies and their underlying mechanisms have come a long way and in 2017 the ILAE (International League Against Epilepsy) reclassified the epilepsies (note the plural!). By using these new terms, we can more effectively say what type of epilepsy we have and what type of seizures we have. This is not only critical for diagnosis and treatment, but also for research, for development of anti-epileptic therapies, and communication around the world.
There are around 60 different types of seizure now, with around 600 genes identified as playing a part in some rare genetic epilepsies.
How seizures are defined and explained starts with identifying the area of onset, i.e., where the seizure STARTS in your brain.
Does the seizure start in one small part of your brain or affect the whole lot all at once?!
Focal onset (seizure starts in one part of your brain)
These seizures start in one part of the brain where you can either be fully aware of what’s going on (focal-aware seizure) or lose some awareness (focal impaired awareness seizure).
You can also have a focal seizure and then have the electrical activity spread to the whole of your brain where it becomes a generalised seizure (or specifically: a focal to bilateral tonic-clonic seizure).
Focal onset seizures can involve movement of the body (motor symptoms)…or not!
These used to be called petit-mal seizures.
See here for more info: Focal seizures
Generalised onset (seizure starts on both sides, all at once!)
These seizures start in both halves of a person’s brain at the same time and can have them moving involuntarily - or not!
Some generalised seizures are absence, atonic, myoclonic, tonic, and tonic-clonic.
Some generalised onset seizures involve physical movements, and some do not.
Generalised onset seizures can involve movement of the body (motor symptoms) or not.
They used to be called grand-mal seizures.
See here for more information: Generalised seizures
Unknown onset (frustrating because we don’t know where it’s starting!)
This is what a seizure is called when it’s not known where in your brain your seizure starts.
Unknown onset is often the case when a person has a seizure alone.
See here for more info: Unknown onset seizures
Types of Focal onset seizure
Focal aware - you totally know what’s going on. Even an aura is a type of focal aware seizure. You usually don’t have involuntary movements. These used to be called Simple partial seizures.
Focal impaired awareness - you lose some awareness during these seizures. you can start picking at your clothes, smacking your lips and more. These used to be called Complex partial seizures.
Atonic seizures - these can actually be generalised onset, meaning they affect both sides of the brain from the start, or they can be focal onset, meaning they start on just one side of the brain.
Myoclonic seizures - these can be generalised onset, meaning that both sides of the brain are affected from the start, or they can be focal onset, meaning that just one side is affected. They are sudden, short-lasting jerks that can affect some or all of a person’s body. They are usually too short to affect a persons’ consciousness.
Focal to bilateral tonic-clonic - these start as a type of focal seizure but then spread in your brain to become a tonic-clonic seizure. These used to be called Secondary generalised tonic-clonic seizures.
Types of Generalised onset seizure
Absence seizures - you are staring into space, unaware of what’s going on. “Absences are a type of generalised onset seizure, meaning both sides of a person’s brain are affected from the beginning of the seizure. The 2 most common types of absence seizure are typical and atypical.” These used to be called Petit-mal seizures. See here for more info: Absence seizures.
Atonic seizures - these can actually be generalised onset, meaning they affect both sides of the brain from the start, or they can be focal onset, meaning they start on just one side of the brain. In an atonic seizure a person’s muscles go limp and they drop to the floor. These used to be called drop attacks. See here for more info: Atonic seizures.
Myoclonic seizures - these can be generalised onset, meaning that both sides of the brain are affected from the start, or they can be focal onset, meaning that just one side is affected. They are sudden, short-lasting jerks that can affect some or all of a person’s body. They are usually too short to affect a persons’ consciousness. See here for more info: Myoclonic seizures.
Tonic - these can be generalised onset, meaning they affect both sides of the brain from the start, or they can be focal onset, meaning they start in just one side of the brain. If a tonic seizure starts in both sides of the brain, all a person’s muscles tighten, and their body goes stiff. If a tonic seizure starts in one side of the brain, then the muscles tighten in just one area of the body. These used to be called Grand-mal seizures. See here for more info: Tonic seizures.
Tonic-clonic - these are the type of epileptic seizure that most people recognise and think of when you say “seizure’’. They can have a generalised onset, meaning that they affect both sides of the brain from the beginning. When this happens, the seizure is called a generalised tonic-clonic or bilateral convulsive seizure. Some seizures start in one side of the brain and then spread to affect both sides. When this happens, it’s called a focal to bilateral tonic-clonic seizure (see above under types of focal-onset seizure). These used to be called Grand-mal seizures. See here for more info: Tonic-clonic seizures.
Having seizures when you don’t have epilepsy
Dissociative - also known as Non-Epileptic Attack Disorder (NEAD) and Psychogenic Non-Epileptic Seizures (PNES), Dissociative seizures are not epileptic seizures but can look very similar! They are often (but not always) the result of mental health trauma.
People with Dissociative seizures are unfortunately often misdiagnosed with epilepsy.
About 90% of people with Dissociative seizures have mental health disorders such as depression, anxiety, somatoform disorders, personality disorders, or post-traumatic stress disorder and deserve to see a professional who can help them.
What can often be helpful is psychotherapy or CBT (Cognitive Behavioural Therapy).
A person can have dissociative seizures as well as epileptic seizures.
See here for more information.
Febrile seizures - these are not epileptic but some children who have them do go on to develop epilepsy.
They can happen when a child has a fever and most often happen between the ages of 6 months and 3 years.
These seizures are usually harmless and almost all children make a complete recovery afterwards.
See here for more information.