🧠 Epilepsy and Seizures: Understanding the Three Major Groups
There are 3 major groups of seizures based on where they start in the brain: generalized onset, focal onset, and unknown onset.
A person with epilepsy may experience just one or more than one kind of seizure. The type of seizure and the symptoms shown depend on what part of the brain the seizures come from.
1. 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 group includes common types of seizures like:
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Tonic-clonic seizures
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Absence seizures
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Atonic seizures
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And more…
2. Focal Onset Seizures
This term helps describe seizures that begin in one specific area or group of cells in just one side of the brain.
Focal seizures are broken down into two main groups based on how aware a person is of their surroundings during the event:
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Focal Onset Aware Seizures: When a person is awake and aware during the seizure, it is called a focal aware seizure. (This used to be called a simple partial seizure.)
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Focal Onset Impaired Awareness Seizures: When a person is confused or their awareness is affected in some way during the seizure, it is called a focal impaired awareness seizure. (This used to be called a complex partial seizure.)
3. Unknown Onset Seizures
A seizure is classified as unknown onset when doctors don’t know where it begins.
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A seizure may also be called an unknown onset if it is not witnessed or seen by anyone. For example, this often happens when seizures occur at night or to a person who lives alone.
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Symptoms can be described as motor (muscles are involved) or non-motor (muscles are not involved).
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As doctors learn more about the seizure events, an unknown onset seizure may later be diagnosed as a focal or generalized seizure.





