What Is Focal Epilepsy?

The seizures begin in one area of the brain

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Focal epilepsy is a type of epilepsy in which the seizures begin in one or more specific areas of the brain. Focal onset seizures can remain as focal seizures with limited symptoms, or they may spread to larger areas of both sides of the brain, causing a secondarily generalized seizure (affecting both sides of the brain) with more significant symptoms.

The distinction between a focal onset seizure and a generalized onset seizure is often made based on diagnostic testing, such as electroencephalogram (EEG) or brain imaging studies. But sometimes, the symptoms can indicate whether a seizure is a focal onset seizure.

One of the main reasons for determining whether a seizure is focal onset or generalized onset is that the treatment for these types of seizures is different.

This article describes the symptoms, causes, diagnosis, and treatment of focal epilepsy, as well as what to expect and how to cope.

Girl with electrodes on head for EEG test

luaeva / Getty Images

Types of Focal Epilepsy 

Several types of epilepsy primarily involve recurrent focal seizures. Sometimes epilepsy involves several seizure types. 

Types of focal seizures include: 

A person can have more than one type of focal seizure. A seizure aura, which occurs at the start of a seizure, is often considered a focal seizure. 

Focal Epilepsy Symptoms 

The effects of a focal seizure can vary, but they also have some features in common. All seizures cause either involuntary movements, sensations, changes in consciousness, or a combination of these. 

A focal onset seizure will cause limited symptoms that do not involve both sides of the body if it does not generalize. If a focal seizure secondarily generalizes, it may begin with limited symptoms before it affects both sides of the body. However, the time focal symptoms last may be so short that it is not noticeable.

Common symptoms of a focal seizure include: 

  • Stiffening of one side of the body or one limb
  • Jerking or shaking of one side of the body or one limb
  • Unusual feelings or perceptions, such as smells 
  • A sense of déjà vu, dread, or unexplained anxiety 
  • Face or mouth movements 
  • Twisting or unusual posture of one side of the body 
  • Diminished responsiveness 

A focal onset seizure will include one or more of these symptoms but will not include all of them. These symptoms may last for about 10 seconds to one minute. 

If a focal onset seizure secondarily generalizes, this means it will involve both sides of the brain. Symptoms of a generalized seizure can include involuntary movements of both sides of the body, unawareness, unresponsiveness, and possibly falling. 

Causes 

Focal seizures occur due to erratic electrical activity in a region of the brain. Symptoms correspond to the affected area of the brain. This area is often referred to as a seizure focus. Sometimes the electrical activity can spread to other areas of the brain, causing more severe symptoms. 

Risk factors for focal epilepsy include: 

  • Developmental brain differences during the prenatal (before birth) period
  • Genetic neurodevelopmental syndromes
  • A stroke (blockage of blood flow or bleeding in the brain)
  • Head trauma, brain contusion (bruising), subdural hematoma (bleeding between the brain and its outer lining)
  • A brain tumor or the spread of cancer into the brain
  • Brain aneurysm (bulging in the wall of a brain artery)
  • Meningitis (infection of the lining around the brain) or encephalitis (brain infection)
  • A cyst or an abscess in the brain

Generally, the tendency to have erratic brain activity is caused by a localized area of brain damage.

Diagnosis 

Focal epilepsy is diagnosed based on a combination of symptoms, medical history, and diagnostic testing.

Sometimes the description of a seizure can be detailed enough so that a healthcare provider can identify the event as a focal seizure. However, often the event is confusing to bystanders, and the person who experienced a focal seizure typically is unable to remember most of the details of the experience.

A history of involuntary movements, unusual sensations, or changes of consciousness may cause a healthcare provider to consider a focal seizure. Sometimes a focal seizure is associated with focal abnormalities on a neurological exam.

Focal abnormalities are neurological changes detected on physical examination that corresponds to a specific area of damage in the brain or spinal cord. These can include weakness, sensory deficits, reflex changes, or vision changes. Often people who have focal epilepsy do not have focal deficits on physical examination.

Diagnostic tests are often used to determine if a person has results consistent with focal seizures.  Tests you may need include: 

  • Electroencephalogram (EEG): This noninvasive diagnostic test is done with metal plates that are placed on the scalp. The pattern of electrical activity in the brain can often show a predisposition to seizures. This test can sometimes differentiate between focal and generalized seizures, but many people who have epilepsy can have a normal EEG.
  • Brain imaging studies: Brain imaging studies, such as computed tomography (CT), magnetic resonance imaging (MRI), and positron-emission tomography (PET), may show abnormalities that correspond to focal seizures. Problems that can be detected with these imaging tests include tumors, stroke, an abscess (a pocket of infection), structural abnormalities, and a brain aneurysm.
  • Genetic testing: Some developmental neurological disorders may be diagnosed using genetic tests.
  • Lumbar puncture: This minimally invasive diagnostic test involves the removal of spinal fluid from the lower part of the back. This test may show evidence of an infection, inflammation, or cancer.

Treatment

Focal epilepsy is treated with anti-epilepsy drugs (AEDs). For most people, these medications are helpful and can reduce the frequency and severity of seizures. 

Some of the medications commonly used to treat focal epilepsy include:

A neurologist (a specialist in nervous system conditions) may prescribe one or more of these to help control focal epilepsy. 

Some people who have epilepsy can attain seizure control through a ketogenic diet. This is a highly restrictive diet that consists of high fat and low carbohydrate intake. The changes in the body that occur with this diet involve the production of ketones, a chemical that is believed to help prevent seizures.

People with certain types of focal epilepsy may be candidates for epilepsy surgery. This type of surgery is invasive and has risks, so it is not considered a first-line treatment.

Lifestyle adjustments are necessary for optimal seizure control. Certain triggers can cause a seizure for a person who has epilepsy.

Lifestyle measures you need to consider include:

  • Avoid drinking alcohol.
  • Get enough rest.
  • Maintain optimal blood glucose (sugar) control if you have diabetes.
  • Do not skip meals.
  • Try to manage stress.

Learn to recognize your seizure warning signs. If you think you are about to have a seizure, avoid potentially dangerous activity and get to a safe place. 

Prognosis 

The outcome of focal epilepsy varies. Focal epilepsy may cause mild and very infrequent seizures that are well-controlled with medication. But it can also cause severe and frequent seizures, with multiple types of seizures that are not well-controlled even with surgery and medication. And the outlook can be somewhere in between.

Some factors that may affect your prognosis are as follows:

  • Typically, epilepsy treated soon after the first seizure occurs will have a better outcome. 
  • Epilepsy damaging a large area of the brain is associated with a worse prognosis than focal epilepsy, resulting in a small area of damage.
  • People with only one type of focal seizure tend to have better seizure control than those with multiple seizure types.
  • Maintaining lifestyle habits that avoid seizure triggers is associated with a better outcome. 

Coping 

If you or your child has focal epilepsy, there are some things that you need to consider in your daily life. Coping involves ensuring you stay in situations in which you can easily get to a safe place if you feel that a seizure is coming on.

You may also need to adjust your activities, including your use of equipment, swimming, and driving. Make sure you do not swim unless you are around others who could rescue you if you have a seizure. Avoid climbing ladders or being in a situation in which you could fall from a height if you have a seizure. 

You may also need accommodations at work or school if you have occasional seizures, miss scheduled sessions, or need time to recover.

Summary 

Focal epilepsy is a type of epilepsy in which people have focal seizures, which are seizures that begin in one area of the brain.

Focal seizures can cause symptoms that affect just one part of the body without complete loss of consciousness. But these seizures can secondarily generalize, which means that they will involve both sides of the brain and cause loss of consciousness and/or involuntary movements on both sides of the body.

Causes of focal epilepsy include brain conditions present at birth, stroke, brain tumors, blood vessel abnormalities in the brain, infections, and/or head trauma. The cause of recurrent seizures can be diagnosed based on the symptoms and diagnostic tests.

Most of the time, focal seizures can be well controlled with medication. Sometimes a ketogenic diet or epilepsy surgery may be required. The outlook is generally good with focal epilepsy, but some people have persistent seizures that are not treated even with medical and surgical therapies.

Living with focal seizures involves making many lifestyle adjustments to avoid seizure triggers and also to prevent harm if a seizure occurs.

A Word From Verywell

Focal epilepsy is the most common type of epilepsy. If you are living with focal epilepsy, be aware that there are effective medical treatments. You can work with your healthcare team to get optimal seizure control.

While treatment can help reduce the impact that epilepsy has on your life, you may need to seek accommodations so that you can safely do the things you need and want to do.

7 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Heidi Moawad, MD
Heidi Moawad is a neurologist and expert in the field of brain health and neurological disorders. Dr. Moawad regularly writes and edits health and career content for medical books and publications.