Health Library

What Is a Seizure?

A seizure (SEE-zhur) is unusual electrical activity in the brain. Normally, electrical activity in the brain involves neurons (nerve cells) in different areas sending signals at different times. During a seizure, many neurons fire all at once.

Depending on where in the brain the seizure happens, it causes changes in behavior, movement, or feelings. A seizure that affects both sides of the brain is called generalized. A seizure that involves only one side of the brain is called focal.

What Is a Generalized Tonic-Clonic Seizure?

During a generalized tonic-clonic seizure, the person loses consciousness and has stiffening and jerking of the muscles. These seizures usually are generalized, starting on both sides of the brain. 

Sometimes, a seizure can begin as a focal seizure on one side of the brain, then spread to both sides. This is called a focal-to-generalized tonic-clonic seizure.

What Are the Signs & Symptoms of a Generalized Tonic-Clonic Seizure?

There are two parts to a generalized tonic-clonic seizure:

During the tonic (stiffening) phase:

• The muscles stiffen.
• The person loses consciousness and falls to the ground.
• They might bite their tongue during the seizure. But do not put anything in their mouth. It won’t prevent the biting and can cause harm.

During the clonic (jerking) phase:

• The arms and legs jerk quickly.

Generalized tonic-clonic seizures usually last 1–3 minutes. During the seizure, the person may lose control of their bladder or bowels.

What Happens After a Generalized Tonic-Clonic Seizure?

After a generalized tonic-clonic seizure, the person may feel confused or irritable, be tired, have a headache, or have other symptoms. This is called the postictal (post-IK-tul) phase. It usually lasts just a few minutes, but can be longer.

What Is an Aura?

An aura is a feeling that people sometimes get just before a seizure. During an aura, a child might:

• have a feeling of already having been in this situation (déjà vu)
• experience an unusual smell or taste
• see flashing lights
• feel a sudden, intense emotion (such as fear)
• feel sick to the stomach

What Causes a Generalized Tonic-Clonic Seizure?

Sometimes, generalized tonic-clonic seizures are genetic (run in families). Other causes include:

• brain injury, tumor, or infection 
• severe electrolyte imbalances (for example, low sodium in the body)
• drug or alcohol use or withdrawal
• gene mutations
• some medical conditions

Sometimes, the cause for generalized tonic-clonic seizures is not known.

How are Generalized Tonic-Clonic Seizures Diagnosed?

If your child had a seizure, the doctor probably will want you to see a pediatric neurologist (a doctor who treats brain, spine, and nervous system problems). The neurologist will ask questions about what happened during the seizure and do an exam.

To find out the type of seizure, the doctor might order tests such as:

• blood tests and urine (pee) tests to look for infections or illnesses
• EEG to measure brain wave activity
• VEEG, or video electroencephalography (EEG with video recording)
• CAT scan, MRI, and PET/MRI scans to get very detailed images of the brain

How Are Generalized Tonic-Clonic Seizures Treated?

Generalized tonic-clonic seizures may be treated with:

• medicines
• special diet (such as the ketogenic diet)
• vagus nerve stimulator therapy
• surgery

Some children stop having generalized tonic-clonic seizures as they get older.

How Can Parents Help?

Your doctor will help you create a plan for your child and talk to you about:

• what medicines your child should take
• if any “triggers” (such as fever, lack of sleep, or medicines) can make a seizure more likely
• any precautions your child should take while swimming or bathing
• whether your child should wear a medical ID bracelet
• if it’s OK for your teen to drive
• how to keep your child safe during a seizure. Share this information with caregivers, coaches, and staff at your child’s school.

Call 911 right away if the seizure lasts more than 5 minutes or if your child has one seizure after another. This is a medical emergency.

If your child has another seizure, keep a record of:

• when it happened
• how long it lasted
• what happened right before the seizure
• what happened during and after the seizure

This information will help the doctor find the best treatment for your child’s seizures.

What Else Should I Know?

If your child has seizures, reassure them that they’re not alone. Your doctor and the care team can answer questions and offer support. They also might be able to recommend a local support group. Online organizations can help too, such as: