Epileptic seizures

Epilepsy is a condition that affects the brain and causes people to have seizures.

But what are epileptic seizures?

What are epileptic seizures?

Epilepsy is a condition that affects the brain and causes frequent seizures. Electrical activity is happening in our brains all the time, as networks of tiny brain cells send messages to each other.

These messages control all our thoughts, movements, senses and body functions. A seizure happens when there is a sudden, intense burst of electrical activity in the brain. This causes the messages between cells to get mixed up. The result is an epileptic seizure.

How a seizure affects you depends on what area of the brain is involved in this intense electrical activity. You might lose consciousness, or you might stay aware of what’s happening around you. You might have strange sensations, or movements you can’t control. Or you might go stiff, fall to the floor and shake.

Some people only have one type of seizure, and some people have more than one type.

Here we explain some of the most common seizure types. We have more information about how epileptic seizures are diagnosed and treated.

How do we describe different types of seizure?

The International League Against Epilepsy is a world-wide organisation of epilepsy professionals. In 2017 they published a paper describing different types of epileptic seizures (a classification system). They updated the words that medical professionals do and don’t use when describing types of seizures. We use the same words here.


Seizure onset

The largest part of the brain is called the cerebrum, and this is divided into two halves, called hemispheres. Epileptic seizures can start in one side (hemisphere), or affect both sides of the brain from the start. Where a seizure starts is known as the seizure onset.

Focal seizures (also called focal onset seizures) start in one side of the brain. Sometimes, a focal seizure can start in one side and then spread to involve both sides of the brain.

Generalised seizures (also called generalised onset seizures) affect both sides of the brain from the start.

Some people experience an ‘aura’ before their seizure starts. This can act like a warning and could include particular thoughts, feelings or sensations. Auras can happen on their own or they can progress to a different type of seizure.

Some people have seizures while they are asleep – you can read more about sleep seizures here.

Types of seizure

  • Focal seizures

    When an epileptic seizure starts in one side of the brain, it’s called a focal onset seizure or a focal seizure. Both terms mean the same thing. These used to be called partial seizures but we no longer use this term.

    Find out more about different types of focal seizures

  • Tonic-clonic seizures

    Tonic-clonic seizures are the type of epileptic seizure most people recognise. In the past they were called grand-mal seizures.

    Tonic-clonic seizures can have a generalised onset, meaning they affect both sides of the brain from the start. 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.

    Find out more about tonic-clonic seizures

  • Absence seizures

    Absence seizures are a type of generalised onset seizure, meaning both sides of your brain are affected from the start. In the past, absence seizures were called petit-mal seizures.

    The two most common types of absence seizure are typical and atypical.

    Find out more about absence seizures


  • Myoclonic seizures

    Myoclonic seizures can be generalised onset, meaning both sides of the brain are affected from the start, or they can be focal onset, meaning just one side is affected.

    Find out more about myoclonic seizures


  • Tonic seizures

    Tonic seizures 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.

    Find out more about tonic seizures


  • Atonic seizures

    Atonic seizures 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. Atonic seizures are sometimes called drop attacks.


    Find out more about atonic seizures

First aid

What to do when someone has a seizure

Take a look at our e-learning course on dealing with seizures

Access e-learning

Non-epileptic seizures

Status epilepticus

Most people with epilepsy have seizures that last a short time and stop by themselves. But sometimes a seizure can last too long and become status epilepticus. Status epilepticus happens when a seizure doesn’t stop in the usual time, or when someone has seizures one after another without recovering in between.

Status epilepticus can happen with any type of seizure, but convulsive (tonic-clonic) status epilepticus is the most dangerous. Convulsive status epilepticus is when a tonic-clonic seizure lasts for five minutes or longer, or when one tonic-clonic seizure follows another without regaining consciousness in between. Convulsive status epilepticus is always a medical emergency.

Epilepsy Action has more information about status epilepticus and emergency treatment on our website.

Download a seizure diary

Seizure diary

A seizure diary is a good way of recording information about your epilepsy.

Download your guide to epilepsy

Your epilepsy

This brochure gives an overview of epilepsy, living with epilepsy and the support you can get from Epilepsy Action.

This information has been produced under the terms of the PIF TICK. The PIF TICK is the UK-wide Quality Mark for Health Information. Please contact website@epilepsy.org.uk if you would like a reference list for this information.
Published: August 2022
Last modified: December 2023
To be reviewed: August 2025
Tracking: L002.06 (previously B037)

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