Epileptic seizures are caused by a disturbance in the electrical activity of the brain. 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.
Are all seizures the same?
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.
Types of seizure
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
- 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.
Focal aware seizures (FAS)
In focal aware seizures (FAS) the person is conscious (aware and alert), will usually know that something is happening and will remember the seizure afterwards.
Tonic clonic seizure
These are the seizures that most people think of as epilepsy. At the start of the seizure the person becomes unconscious, their body goes stiff and if they are standing up they usually fall backwards.
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.
In myoclonic seizures the person is conscious, but they are classified as generalised seizures. This is because the person is likely to have other seizures (such as tonic clonic seizures) as well as myoclonic seizures.
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.
A person's seizures usually last the same length of time each time they happen and stop by themselves. However, sometimes seizures do not stop or one seizure follows another without the person recovering in between. If this goes on for 30 minutes or more it is called status epilepticus or ‘status’.
Status is not common, but it can happen in any type of seizure and the person may need to see a doctor. Status in a tonic clonic (convulsive) seizure is a medical emergency and the person will need urgent medical help. Do not wait until the seizure has lasted 30 minutes before calling for an ambulance.