Information for the public
Types of seizure
There are many different types of epileptic seizure, but they are divided into two main groups (focal or generalised) depending on the source of the seizure within the brain.
Focal (or partial) seizures are seizures that start in one part of the brain. These seizures may take many different forms depending on the part of the brain that is affected. They may involve a change of movement or behaviour; a person may remain aware of their surroundings during a seizure, or they may lose awareness.
Generalised seizures are more distributed and affect both sides of the brain at once. There are different types of generalised seizure, the most recognised of which is the 'tonic–clonic seizure' (where the person goes stiff and then has jerking movements). During a generalised seizure, the person may lose consciousness, fall or have muscle spasms.
Sometimes a focal seizure spreads from one side of the brain to the other – when this happens this is known as secondary generalisation.
Some people with epilepsy have only one type of seizure, and others have more than one type. The type of seizures a person has may change over time. In this information, the term 'seizure' could mean 'seizures' for people who have more than one type of seizure.
With increasing advances in technology, it is possible to give a cause of the epileptic seizures in a growing number of cases (for example, damage to the brain during a difficult birth, or a head injury). However, sometimes there is no known cause.