What are focal onset seizures?

Focal onset seizures are seizures that start in one area of the brain. They usually last less than two minutes. Focal onset seizures are different from generalized seizures, which affect all areas of the brain.

Doctors used to call focal onset seizures partial seizures. But in April 2017, the International League Against Epilepsy released new classifications that changed the name from partial seizures to focal onset seizures.

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According to Johns Hopkins Medicine, there are three types of focal onset seizures. Knowing what type of focal onset seizure a person has helps a doctor determine the best treatment.

Focal onset aware seizuresPerson maintains consciousness but will likely experience changes in movement.
Focal onset impaired awareness seizuresPerson either loses consciousness or experiences a change in consciousness.
Focal onset seizures that secondarily generalizeSeizures start in one region of the brain but then spread to other regions of the brain. Person may experience convulsions, muscle spasms, or affected muscle tone.

Focal onset aware seizures

These seizures were formerly known as simple partial seizures or focal seizures without a loss of consciousness. A person with this seizure type doesn’t lose consciousness during the seizure. However, depending on the area of the brain affected, they may have changes in emotion, body movements, or vision.

Jacksonian seizures, or Jacksonian march, are a type of focal onset aware seizure that usually affect only one side of the body. Twitching usually begins in one small area of the body, like a toe, finger, or corner of the mouth, and “marches” to other areas of the body. The person is conscious during a Jacksonian seizure and may not even be aware that a seizure is occurring.

Focal onset impaired awareness seizures

These seizures were formerly known as complex partial seizures or focal dyscognitive seizures. During this type of seizure, a person will experience a loss of consciousness or change in consciousness level. They will not know they had the seizure, and they may stop responding to their environment.

Sometimes, a person’s behavior may be mistaken for not paying attention or even ignoring others when they are actually having a seizure.

Focal onset seizures that secondarily generalize

These seizures may start in one part of the brain and then spread to other parts. Some doctors consider the focal seizure an aura or warning of the generalized seizure that is to come.

This seizure will start in only one area of the brain, but then start to spread. As a result, the person may have convulsions, muscle spasms, or affected muscle tone.

The symptoms of a focal onset seizure, whatever the type, depend on the area of the brain that’s affected. Doctors divide the brain into lobes or regions. Each has different functions that are interrupted during a seizure.

In the temporal lobe

If the temporal lobe is affected during the seizure, it can cause:

  • lip smacking
  • repeated swallowing
  • chewing
  • fright
  • déjà vu

In the frontal lobe

Seizures in the frontal lobe can cause:

  • difficulty speaking
  • side-to-side head or eye movements
  • stretching of the arms in an unusual position
  • repeated rocking

In the parietal lobe

A person with a focal onset seizure in the parietal lobe may experience:

  • numbness, tingling, or even pain in their body
  • dizziness
  • vision changes
  • a feeling as if their body does not belong to them

In the occipital lobe

Focal seizures in the occipital lobe can cause:

  • visual changes with eye pain
  • a feeling as if the eyes are rapidly moving
  • seeing things that aren’t there
  • fluttering eyelids

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People who have experienced a traumatic brain injury in the past are at greater risk of focal onset seizures. Other risk factors for these seizures include a history of:

Age can also be a risk factor. People are more likely to have a seizure in early childhood or after age 60, according to the Mayo Clinic. However, it’s possible a person could have no risk factors and still have a focal onset seizure.

Physical exam

A doctor will start by asking about your medical history and conducting a physical exam. Sometimes a doctor will make the diagnosis based on the explanation of your symptoms. However, focal onset seizures can cause symptoms that are similar to other conditions. Examples of these conditions include:

The doctor will try to rule out other conditions while determining if your symptoms could mean you are having focal onset seizures.

Diagnostic tests

A doctor may also use diagnostic tests to determine if a person could be having seizures. Examples of these tests include:

Electroencephalogram (EEG): This test measures and locates the region of abnormal electrical activity in the brain. However, because a person with focal onset seizures likely doesn’t have constant disturbances in electrical activity, this test may not detect this seizure type unless they later generalize.

Magnetic resonance imaging (MRI) or computed tomography (CT): These imaging studiescan help a doctor identify potential underlyingcauses associated with focal onset seizures.

Focal seizures can persist for minutes, hours, or in rare cases, days. The longer they last, the more difficult they are to stop. In such cases, urgent medical care is often needed and IV medications are used to stop the seizure. Doctors will then focus on preventing the seizures from happening again.

Examples of the treatments for seizures include:


Antiseizure medications may be taken alone or in combination to reduce the likelihood that a seizure will occur. Examples of these medications include lamotrigine (Lamictal) and carbamazepine (Tegretol).


Because focal onset seizures occur in one area of the brain, a doctor may recommend surgery to remove that specific area to reduce the incidence of seizures. This is usually done if patients require multiple medications to control their seizures or if the medications have limited efficacy or intolerable side effects. Although brain surgery always poses risks, your doctors may be able to cure you of your seizures if they can clearly identify a single source of the seizures. However, some parts of the brain can’t be removed.


A device called a vagus nerve stimulator can be implanted to send bursts of electrical energy to the brain. This can help reduce the incidence of seizures. However, some people will still need to take their antiseizure medications even with the device.

Dietary therapy

Some people with partial seizures have found success in a special diet known as a ketogenic diet. This diet involves eating few carbohydrates and higher amounts of fat. However, the diet’s restrictive nature can make it difficult to follow, especially for younger children.

A doctor may recommend using all of these therapies or a combination of them as a means to treat focal onset seizures.

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It may be difficult for a person to recognize when they’re having a focal seizure, depending on their symptoms. If a person has lost awareness, or if friends and family tell them they are often staring blankly or appear as if they’re not listening, these can be signs that a person should seek medical attention. Also, if a seizure lasts more than 5 minutes, it’s time to call the doctor or go to the emergency room.

Until a person sees their doctor, they should keep a journal of their symptoms and how long they last to help the doctor track the patterns of possible seizures.