Introduction

Introduction

If someone is diagnosed with epilepsy, it means they have a tendency to have seizures (sometimes called fits). Epilepsy is usually only diagnosed after the person has had two seizures or more.

Seizures can happen in any part of the brain. The brain is responsible for all the functions of our mind and body. What any of us experiences during a seizure will depend on where in the brain the seizure is happening. 

These web pages give a brief explanation of the most common types of epileptic seizure.

The structure of the brain

Why seizures happen

Electrical activity is happening in our brain all the time. A seizure happens when there is a sudden burst of intense electrical activity. This intense electrical activity causes a temporary disruption to the way the brain normally works, meaning that the brain’s messages become mixed up. The result is an epileptic seizure.

In these web pages, the term ‘epileptic activity’ is used to talk about this intense electrical activity.

When seizures start

Seizures can start at any age. Certain seizure types are more likely to start at certain times of life. For example, absence seizures mainly happen in childhood. Some children go on to have them when they are adults, but this is rare. In older people, focal seizures (also called partial) are the most common seizure type.

Seizure classification

The International League Against Epilepsy (ILAE), a world-wide organisation of epilepsy professionals, has compiled a list of the names of different seizure types. This is called the ILAE seizure classification. The names given to different types of seizures are based on this classification.

Giving seizures the right names is important for doctors. This is because some drugs and treatments can help some seizure types but not others.

Seizure types

There are many different types of seizure. They can be classed by where in the brain the epileptic activity starts.

Focal (partial) seizures

In these seizures the epileptic activity starts in just a part of your brain. You may remain alert during this type of seizure, or you may not be aware of what is happening. You may have movements that you can’t control, or unusual sensations or feelings. Sometimes, onlookers may not be aware that you are having a seizure.

Focal seizures can be very brief or last for minutes. Sometimes, epileptic activity starts as a focal seizure, spreads to the rest of your brain and becomes a generalised seizure.

• More information about focal (partial) seizures

Generalised seizures

These seizures involve epileptic activity in both hemispheres (halves) of your brain. You usually lose consciousness during this type of seizure, but sometimes it can be so brief that no one notices. The muscles in your body may stiffen and/or jerk. You may fall down.

• More information about generalised seizures