Epileptic seizures

There are many different types of epileptic seizure. Any of us could potentially have a single epileptic seizure at some point in our lives.This is not the same as having epilepsy, which is a tendency to have seizures that start in the brain. 

Neurons firing

There are different types of epileptic seizures, but they all start in the brain.

There are other types of seizures which may look like epileptic seizures but they do not start in the brain.

Some seizures are caused by conditions such as low blood sugar (hypoglycaemia) or a change to the way the heart is working. Some very young children have 'febrile convulsions' (jerking movements) when they have a high temperature. These are not the same as epileptic seizures. On this page when we use the word ‘seizure’ we mean epileptic seizure.

A new method to group seizures

In March 2017 the International League Against Epilepsy (ILAE), a group of the world's leading epilepsy professionals, introduced a new method to group seizures.This gives doctors a more accurate way to describe a person's seizures, and helps them to prescribe the most appropriate treatments.

Seizures are divided into groups depending on where they start in the brain (onset), whether or not a person's awareness is affected and whether or not seizures involve other symptoms, such as movement.

Depending on where they start, seizures are described as being focal onset, generalised onset or unknown onset.

What is a focal onset seizure?

One of the new groupings is focal onset seizures which start in one part of the brain and may affect a large part of one hemisphere or just a small area in one of the lobes. 

Here's our flowchart showing a breakdown of a focal onset seizure with information on the new classifications:

 

Seizure classifications - infographic

 

What is a generalised seizure?

The grouping 'generalised onset' covers seizures which affect both sides of the brain at once and happen without warning. Here's our flowchart showing a breakdown of a generalised onset seizure with information on the new classifications.

 

Seizure classifications - infographic

 

Seizure types

Absence seizures

Absence seizures are more common in children than adults and can happen very frequently. During an absence a person becomes unconscious for a short time. They may look blank and stare, or their eyelids might flutter. They will not respond to what is happening around them. If they are walking they may carry on walking but will not be aware of what they are doing.

Myoclonic seizures

Myoclonic means ‘muscle jerk’. Muscle jerks are not always due to epilepsy (for example, some people have them as they fall asleep). Myoclonic seizures are brief but can happen in clusters (many happening close together in time) and often happen shortly after waking.

Tonic and atonic seizures

In an atonic seizure (or 'drop attack') the person’s muscles suddenly relax and they become floppy. If they are standing they often fall, usually forwards, and may injure the front of their head or face. Like tonic seizures, atonic seizures tend to be brief and happen without warning. With both tonic and atonic seizures people usually recover quickly, apart from possible injuries.

Seizure triggers

Triggers are situations that can bring on a seizure in some people with epilepsy. Some people's seizures are brought on by certain situations. Triggers can differ from person to person, but common triggers include tiredness and lack of sleep, stress, alcohol, and not taking medication. For some people, if they know what triggers their seizures, they may be able to avoid these triggers and so lessen the chances of having a seizure.

Why do seizures happen?

Your brain controls the way you function. Inside your brain, millions of nerve cells (neurones) pass messages via electrical signals to each other. During a seizure these electrical signals are disrupted and this affects how you feel or what you do while the seizure is happening.

Seizure diaries

Keeping a seizure diary can be useful to help you record when your seizures happen and to see whether there are any specific triggers for your seizures. Sometimes, known triggers can be avoided to help reduce the number of seizures.

All about the brain

The brain is a highly complex organ and the centre of the nervous system. Here is more detail about the different areas of the brain.

Seizures leaflet

Want to know more?

Order or download our seizures leaflet:

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