Seizures That Don't Affect the Entire Brain

Focal epilepsy is when people have recurrent seizures that may cause symptoms affecting only one side of the body. Seizures in epilepsy can be focal or generalized.

Focal epilepsy seizures, sometimes called partial seizures, involve more limited symptoms than generalized epilepsy seizures. A key difference is that a small area of brain damage usually causes focal epilepsy seizures. Generalized seizures can start on both sides of the brain, although some forms of generalized seizures start on one side and then secondarily generalize to both sides.

Focal epilepsy seizures can begin at any age—from infancy to adulthood—and usually are controlled with medication or other interventions. You may need to take precautions if you or your child has focal epilepsy—such as not swimming alone and avoiding alcohol.

Medical care and lifestyle considerations allow you to enjoy a normal life and manage your condition safely. This article will describe the symptoms and effects of focal epilepsy, causes, treatment, and seizure prevention.

Effect of Focal Epilepsy Symptoms

Focal epilepsy seizures cause either involuntary movements, unexpected sensations, changes in consciousness, or a combination of these symptoms.

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 epilepsy 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.

Secondary Generalization

A focal onset seizure can remain a focal seizure throughout the whole episode, or it can secondarily generalize, becoming a generalized seizure. This means that the seizure can spread to both sides of the brain, and the symptoms can affect both sides of the body.

When that happens, the focal seizure symptoms may last for a short time, and the seizure can appear exactly like a generalized onset seizure, which is a seizure that starts on both sides of the brain.

Symptoms of a generalized seizure include involuntary movements on both sides of the body, unawareness, and unresponsiveness.

How Focal Epilepsy Is Diagnosed

A diagnosis of focal epilepsy is based on a combination of:

  • Medical history (including risk factors)
  • Symptoms
  • Physical examination
  • Diagnostic tests

Often, an electroencephalogram (EEG) can detect a seizure focus, or a brain imaging test can identify a change that’s consistent with focal epilepsy.

Are Focal Epilepsy Seizures Chronic?

For most people, focal epilepsy can be well managed with medication, but it typically requires lifelong treatment.

Focal epilepsy seizures can bring safety risks. Having seizures can result in serious injuries and physical harm from falling or accidents that could occur during a seizure. Treatment for preventing focal seizures is the best way to avoid these types of harmful outcomes.

People rarely grow out of focal epilepsy because a small area of damage in the brain usually causes this type of epilepsy. Focal epilepsy causes can be present from birth or may develop later in life due to problems such as head trauma or a stroke.

These types of brain damage do not heal on their own, but the symptoms that they cause can sometimes be managed with treatment.

Sometimes focal epilepsy can be cured if the seizures are caused by removable growths in the brain, like a tumor or a brain aneurysm (a bulge in the wall of an artery in the brain).

If they’re not treated, these growths can cause significant disabilities—including vision loss or permanent paralysis. But if growths in the brain are surgically removed or treated with radiation therapy, then sometimes the seizures may stop happening, and associated disabilities may be prevented.

Types of Focal Epilepsy

The classification systems for focal epilepsy are:

  • By location in the brain: Frontal lobe epilepsy, temporal lobe epilepsy, parietal lobe epilepsy, thalamic epilepsy
  • By effect on consciousness: Simple focal epilepsy (does not affect consciousness), complex focal epilepsy (causes impaired consciousness)
  • Childhood focal epilepsy syndromes: Self-limited epilepsy with centrotemporal spikes, self-limited epilepsy with autonomic seizures, childhood occipital visual epilepsy, photosensitive occipital lobe epilepsy

Treatment and Focal Epilepsy Prevention

Treatment for focal epilepsy is intended to control the condition by preventing seizures. Antiepileptic drugs (AEDs) are the most common treatments for focal epilepsy, but sometimes epilepsy surgery or surgically implanted devices for seizure control may be options for some people.

Medication for focal epilepsy include:

  • Tegretol (carbamazepine)
  • Topamax (topiramate)
  • Keppra (levetiracetam)
  • Dilantin (phenytoin)
  • Trileptal (oxcarbazepine)
  • Zonegran (zonisamide)
  • Lamictal (lamotrigine)

You and your healthcare provider, usually a neurologist, will discuss your symptoms and seizure types to determine which treatment is likely to be most effective for you.

Epilepsy Surgery

Sometimes it’s clear from diagnostic testing that focal epilepsy is starting from a specific area of the brain. In some circumstances, surgery can help treat the seizures.

For example, if focal seizures are caused by a single brain tumor, a brain aneurysm, or a small area of developmental change in the brain from birth, the area can sometimes be treated surgically to prevent seizures.

Additionally, some epilepsy devices are designed to provide electrical stimulation to the brain at a frequency that suppresses seizures from occurring.

Surgical interventions for focal epilepsy include:

  • Brain tumor removal
  • Brain aneurysm repair
  • Lesionectomy, creating a lesion (cut) in a congenital (from birth) seizure area
  • Resection (removing an area of the brain that causes seizures)
  • Vagus nerve stimulation

What Causes One-Sided Seizures in the Brain?

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 secondary generalization and more severe seizure symptoms.

Risk factors for focal epilepsy include:

  • Developmental brain differences during prenatal (before birth) development
  • Genetic neurodevelopmental syndromes
  • Damage from a stroke (blockage of blood flow or bleeding in the brain)
  • Head trauma, which can cause a brain contusion (bruising), subdural hematoma (bleeding between the brain and its outer lining), or epidural hematoma (blood between the outer lining of the brain and the skull)
  • A brain tumor or the spread of cancer into the brain
  • Brain aneurysm
  • Meningitis (infection or inflammation of the lining around the brain) or encephalitis (brain infection)
  • A cyst or an abscess in the brain

Sometimes, seizures are the first sign that someone has an underlying risk factor, but the risk factor is sometimes known before seizures occur.

During a Focal Epilepsy Seizure: Safety and Support

While focal epilepsy seizures can sometimes have minor symptoms, the seizures can be dangerous or might lead to injuries. Focal epilepsy seizures that generalize could also cause you to have significant physical risks from falling.

If you have recurrent focal epilepsy seizures, it’s important that you take precautions because you could be at risk of having a breakthrough seizure even if they are well controlled.

Things to be cautious about include:

  • Swimming: Don’t swim alone, and make sure that you are with a person who could rescue you if necessary (even if you’re swimming in shallow water).
  • Driving: States have different regulations about driving and epilepsy. Discuss your risk with your neurologist.
  • Using equipment: Some types of machinery can be dangerous to yourself or others if you have a seizure. This may include construction equipment or commercial vehicles. Make sure you aren’t working in situations that could be hazardous in the case of a seizure.
  • Childcare: If you are a parent or child care worker, you might need to ensure that there is another adult around in case you have a seizure.

Safety considerations are specific to your seizure symptoms, lifestyle, and responsibilities. You might benefit from advice and tips that you could gain by joining a support group.

During a Seizure

If someone who has epilepsy is having a seizure while you are around, stay nearby until the episode is over and the person is fully alert. Do not try to stop their movements or put anything in their mouth.

When they are fully alert, help them find a safe place to sit. Explain what happened to them.

You should get emergency help by calling 911 if you are not familiar with their seizure history. If you know the person and their seizure history pattern and this seizure is part of that pattern, you may not need to call 911.

Check for their emergency information and ensure they make it home safely, preferably with a trusted family member or friend monitoring them at home.

Calling 911 is recommended in these cases:

  • They are having a prolonged seizure or sequential seizures lasting for longer than five minutes.
  • You see they are injured.
  • They don’t wake up right after the seizure.
  • They are having difficulty breathing.
  • The seizure happened in water.
  • You know the person has never had a seizure before.
  • You know that the person is pregnant or has diabetes or heart disease.


Focal epilepsy seizures are seizures that affect one area of the brain and one side of the body, sometimes with subtle symptoms affecting awareness. A focal seizure can generalize and affect both sides of the brain and body. It can often be hard to tell the difference between focal seizures and generalized seizures.

Since the medical therapy of focal epilepsy and generalized epilepsy differs, diagnostic tests are used to distinguish focal epilepsy from generalized epilepsy.

It’s very important that you stay on track with your medical therapy if you have epilepsy. Getting the right treatment can help you live a full life with minimal interruptions due to your epilepsy.


Source:, Smita Patel, MD