Types of Seizures
New terms to describe and classify seizures have been developed by the International League Against Epilepsy. This was done to make the names of seizures more accurate, less confusing, and more descriptive of what is happening.
The new terms consider these important areas when describing seizures.
- The onset or beginning of a seizure: Where seizures start in the brain tells a lot about what may occur during a seizure, what other conditions or symptoms may be seen, how they may affect someone and, most importantly, what treatment may be best for that seizure type. When we don’t know if a seizure is focal or generalized in onset, the wrong treatment may be used. Or a person may not be offered a treatment that has the best chance of helping.
- A person’s level of awareness during a seizure: Whether a person is aware or not tells a lot about the type of seizure. It’s also very important to know for a person’s safety.
- Whether movements happen during a seizure: Seizures can also be described by whether motor symptoms occur. When no motor symptoms happen, it can be called a non-motor seizure. This level of description does not need to be used all the time, especially when generally describing or talking about seizures. Yet other times you may find the motor terms helpful.
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How Are Seizures Classified Now?
There are now 3 major groups of seizures.
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 seizure types like generalized 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.
- Focal onset aware seizures: When a person is awake and aware during a seizure, it’s called a focal aware seizure. This used to be called a simple partial seizure.
- Focal onset impaired awareness: When a person is confused or their awareness is affected in some way during a focal seizure, it’s called a focal impaired awareness seizure. This used to be called a complex partial seizure.
- A focal seizure can also spread to both sides of the brain and become tonic-clonic (focal to bilateral tonic-clonic). People with this seizure type usually have an aura before the tonic-clonic seizure.
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.
- As more information is learned, an unknown onset seizure may later be diagnosed as a focal or generalized seizure.
Listen to Drs. Joe Sirven and Bob Fisher discuss changes in classification in a Hallway Conversations podcast:
How Are Different Symptoms During A Seizure Described?
Many different symptoms happen during a seizure. This new classification separates them simply into groups that involve movement.
For generalized onset seizures:
- Motor symptoms may include sustained rhythmical jerking movements (clonic), muscles becoming weak or limp (atonic), muscles becoming tense or rigid (tonic), brief muscle twitching (myoclonus), or epileptic spasms (body flexes and extends repeatedly).
- Non-motor symptoms are usually called absence seizures. These can be typical or atypical absence seizures (staring spells). Absence seizures can also have brief twitches (myoclonus) that can affect a specific part of the body or just the eyelids.
For focal onset seizures:
- Motor symptoms may also include jerking (clonic), muscles becoming limp or weak (atonic), tense or rigid muscles (tonic), brief muscle twitching (myoclonus), or epileptic spasms. There may also be automatisms or repeated automatic movements, like clapping or rubbing of hands, lipsmacking or chewing, or running.
- Non-motor symptoms: Examples of symptoms that don’t affect movement could be changes in sensation, emotions, thinking or cognition, autonomic functions (such as gastrointestinal sensations, waves of heat or cold, goosebumps, heart racing, etc.), or lack of movement (called behavior arrest).
For unknown onset seizures:
- Motor seizures are described as either tonic-clonic or epileptic spasms.
- Non-motor seizures usually include a behavior arrest. This means that movement stops – the person may just stare and not make any other movements.
What If I Don’t Know What Type Of Seizures I Or My Loved One Have?
It’s not unusual that a person doesn’t know the type of seizure they have. Often seizures are diagnosed based on descriptions of what an observer has seen. These descriptions may not be fully complete, or one can’t tell where a seizure begins from this information.
When seizures are difficult to diagnose or seizure medicines are not working to stop seizures, talk to your doctor or treating health care provider.
- Seeing an epilepsy specialist or having an evaluation at an epilepsy center can help find out if you are having seizures. Not all events are due to epilepsy.
- An epilepsy center help you explore other treatment options, such as surgery, devices, dietary therapy, new or add-on seizure medications, or a clinical trial.
- Having imaging tests like an MRI (magnetic resonance imaging) scan to look at the brain and EEG (electroencephalogram) tests to record the electrical activity of the brain are very helpful to diagnose types of seizures and epilepsy properly.
- Keep asking questions so you get the right tests and right treatment for your type of seizures and epilepsy.
How Can I Learn More?
Read through the different seizure types listed in this section.
Take information to your healthcare team along with a description of your seizures. Ask family or friends to write down what they see happening or to take a video. Then ask for help understanding your type of seizures.
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