Has your doctor spoken to you about ‘focal onset’ or ‘generalized onset’ seizures? Physicians use these words to describe where in the brain a seizure started - but medical terms can sometimes be confusing.
If you’re unsure about the difference between generalized and focal seizures, ask your doctor for more information. The following article provides an overview of some of the differences.
Focal vs generalized seizures vs unknown vs unclassified
Seizures happen because of uncontrolled, abnormal electrical activity in the brain. There are many different kinds of seizures and types of epilepsy.
If someone appears to be having epileptic seizures, the treatment team will typically try to identify where in the brain their seizures start. As the Epilepsy Foundation explains, if doctors can locate where the seizures start, it might affect the kind of treatment they offer to their patients.
The pattern of electrical discharges can be categorized in one of four ways: focal, generalized, unknown (whether focal or generalized) or unclassified.
If you’re unsure whether you have focal or generalized seizures, speak with your doctor.
What is a generalized seizure?
A generalized seizure is when the electrical discharge happens on both sides of the brain and starts at about the same time. About 40% of people with epilepsy have generalized onset seizures.
Types of generalized seizure include:
- Generalized tonic-clonic
- Myoclonic-tonic-clonic
- Absence-to-tonic-clonic
- Typical absence
- Atypical absence
- Myoclonic absence
- Eyelid myoclonia with or without absence
- Myoclonic
- Negative myoclonic
- Clonic
- Epileptic spasms
- Tonic
- Myoclonic-atonic
- Atonic
What causes a focal seizure?
With a focal seizure, the electrical activity begins on one side of the brain. About 60% of people with epilepsy experience focal onset seizures.
Types of focal seizure include:
- Focal consciousness preserved
- Focal consciousness impaired
- Focal to bilateral tonic-clonic seizure
Unknown
Sometimes, it is unclear whether the seizure is focal or generalized, or there isn’t enough information to know for sure. These are described as seizures with an ‘unknown’ origin.
Unclassified
Sometimes, an individual’s seizures remain unclassified. If a doctor believes a person has had an epileptic seizure but does not have enough information to classify the type, it remains unclassified.
Diagnosing focal vs generalized seizures
To help diagnose whether you have focal or generalized onset seizures, the treatment team may use a few techniques, including:
- Medical history
- Imaging and monitoring technologies (which may include EEG, CT and MRI scans, among other techniques)
- Blood tests
- Developmental, neurological, and behavioral tests
Sometimes, people who may have epilepsy are referred to an epilepsy monitoring unit, which is a specialized medical center that can support diagnosis.
Learn more about seizures
Focal vs generalized seizures is the main categorization of seizure types. But within each of these two categories there are many subtypes of seizures. Learn more about specific types of seizures in our blogs.
