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:
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.
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.
In focal aware seizures (FAS), previously called simple partial seizures, the person is conscious (aware and alert) and will usually know that something is happening and will remember the seizure afterwards.
Focal impaired awareness seizures (FIAS) affect a bigger part of one hemisphere (side) of the brain than focal aware seizures. This seizure was previously called complex partial 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.
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.
These are the seizures that most people think of as epilepsy. the person becomes unconscious their body goes stiff and if they are standing up they usually fall backwards. they jerk and shake as their muscles relax and tighten rhythmically.
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