Seizures involve sudden, temporary, bursts of electrical activity in the brain that change or disrupt the way messages are sent between brain cells. These electrical bursts can cause involuntary changes in body movement or function, sensation, behavior or awareness.

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Every brain has the potential to seize. A person with epilepsy has a lower seizure threshold – this means they are more likely to have seizures than people without epilepsy.

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It is important to note the distinction between seizures and epilepsy. A seizure is an event and can be a symptom of other medical problems.

Not all seizures are the same. Many people with epilepsy have more than one type of seizure and may have other symptoms of neurological problems as well. There are now 3 major groups of seizures:

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Generalized onset seizures: These seizures affect both sides of the brain or groups of cells on both sides of the brain at the same time. This term was used before and still includes seizures types like tonic-clonic, absence, or atonic to name a few.

Focal onset seizures: The term focal is used instead of partial to be more accurate when talking about where seizures begin. Focal seizures can start in one area or group of cells in one side of the brain.

Unknown onset seizures: When the beginning of a seizure is not known, it’s now called an unknown onset seizure. A seizure could also be called an unknown onset if it’s not witnessed or seen by anyone, for example when seizures happen at night or in a person who lives alone.

Some people may find that seizures occur in a pattern or are more likely to occur in certain situations. Sometimes these connections are just by chance, but other times it’s not. Keeping track of any factors that may come before a seizure (also called seizure triggers) can help you recognize when a seizure may be coming. You can then be prepared and learn how to lessen the chance that a seizure may occur at this time.

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Some people will notice one or two triggers very easily. For example, their seizures may occur only during sleep or when waking up. Other people may notice that some triggers bother them only when a lot is going on at once or during a "high risk" time for them, like when they are under a lot of stress or sick.

Epilepsy syndromes are defined by a cluster of features.

These features may include:

• Type or types of seizures

• Age at which the seizures begin

• Causes of the seizures

• Whether the seizures are inherited

• The part of the brain involved

• Factors that provoke the seizures

• How severe and how frequent the seizures are

• A pattern of seizures by time of day

• Certain patterns on the EEG (electroencephalogram), during and between seizures

• Brain imaging findings, for example, MRI (magnetic resonance imaging) or CT (computed tomography) scan

• Genetic information

• Other disorders in addition to seizures

• The prospects for recovery or worsening