Lennox-Gastaut Syndrome (LGS)

Lennox-Gastaut syndrome is a type of childhood epilepsy that’s particularly severe. This condition causes multiple types of seizures that can lead to permanent brain damage. That damage often results in learning difficulties and other disabilities. Possible treatments include medication, implanted devices, ketogenic diet and brain surgery.


What is Lennox-Gastaut syndrome?

Lennox-Gastaut syndrome (LGS) is a type of severe epilepsy that appears during childhood. This condition is particularly serious and difficult to treat, and it usually has severe effects. However, there are several newer medications approved to treat this condition, and there are also possible nonmedication treatments.


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Who does it affect?

Lennox-Gastaut syndrome is a condition that almost always starts before age 10, with a diagnosis most likely to happen between ages 3 and 5. It’s slightly more common in male children.

How common is this condition?

Lennox-Gastaut syndrome is rare, with an estimated 1 to 2 cases out of every 1 million people. This condition makes up about 1% to 2% of all epilepsy cases.


How does this condition affect my body?

Epilepsy refers to a family of conditions that cause malfunctions in how brain cells send signals to each other. Lennox-Gastaut syndrome is a particularly severe type of epilepsy for the following reasons:

  • LGS causes multiple types of seizures. Some of these types of seizures are more likely to cause severe injuries.
  • The seizures often damage the brain itself. LGS very commonly causes severe brain damage, leading to learning difficulties and developmental setbacks. That means children with this condition may permanently lose part or all of some abilities they’d already learned, such as walking or talking.
  • LGS usually resists treatment. Medications are the first line of treatment for this condition, but it’s common that multiple medications are necessary. And while multiple medications can help this condition, it’s rare that medications alone can completely stop seizures.

Symptoms and Causes

What are the symptoms of LGS?

There are many different possible symptoms of LGS. Some of them are visible in everyday life or activities. Others are only visible during a seizure.

Learning and behavior problems

LGS usually causes learning and behavior problems, which start soon after seizures begin and often worsen over time as seizures continue. Those learning and cognitive problems are often permanent and last into adulthood.

Children with LGS usually struggle with learning, making friends and communicating with others. They may also have trouble controlling emotions. Many children will show signs similar to those seen in children with autism spectrum disorder.

Seizure stages

Seizures usually happen in three stages:

  • Prodrome or aura. This stage happens often, but not always, before a seizure. This often feels unpleasant. It can involve changes in your vision or other senses or changes in mood and behavior.
  • Seizure. This is the seizure itself, which may happen differently depending on the type of seizure (see below for more about the potential types).
  • Post-seizure recovery. This is after a seizure ends. This is when a person regains full consciousness.

Types of seizures

LGS usually involves multiple seizure types. The most likely types of seizures and their effects are as follows:

  • Atonic (A-tonic).
  • Tonic.
  • Atypical absence.

While most of the seizures themselves are short, people with LGS commonly have "clusters" of seizures, which means several seizures in a short period. In more than two-thirds of cases, people with LGS will have “status epilepticus." That’s when one of two things happens:

  • A seizure that lasts for between five and 30 minutes.
  • More than one seizure within 30 minutes, and the person doesn’t recover to full consciousness between seizures.

Status epilepticus is a medical emergency. It’s especially dangerous because it can cause permanent brain damage and death.

Atonic seizures

  • Limpness or loss of muscle control. Sometimes referred to as "drop attacks" because they cause a person to go limp as if all the muscles in their body stopped working. These are particularly dangerous because they can cause a person to fall. Without any muscle control, the person having the seizure can’t break their fall or protect their head, neck, chest or back. That can cause severe or even life-threatening injuries.
  • Partial loss of consciousness. People having atonic seizures may not fully lose consciousness or pass out from the seizure itself.
  • Short duration. These seizures are usually short-lived, lasting only a few seconds.

Tonic seizures

  • Muscle stiffness throughout the body. Tonic seizures are when a person’s body goes uncontrollably rigid or stiff as most or all of the muscles in their body contract.
  • Feet and shoulders on the ground with back arched upward. While on the ground, their arms may stretch over their head, or they might tense up so their arms bend and their elbows point away from their body while their fists point toward their jaw.
  • Happen most often during sleep. These usually happen during sleep but are possible during the daytime. When they happen while a person is awake, they can cause a person to fall, putting them at risk of injury.
  • Short duration. These usually last between several seconds and a minute.

Atypical absence seizures

  • Staring at nothing. These seizures cause loss of consciousness, but with an open-eyed stare. That’s why absence seizures are often mistaken for daydreaming, distraction or absentmindedness.
  • Repetitive movements. Atypical absence seizures usually involve eye or mouth movements. The movements can be in the mouth, eyes or hands.
  • Short duration. These usually last no more than several seconds.

Other symptoms and their seizure types

  • Full-body convulsions. Tonic-clonic seizures (once known as “grand mal” seizures) start similarly to tonic seizures as mentioned above, but also have another phase to them. The clonic phase involves convulsions, one of the best-recognized features of seizures. Tonic and tonic-clonic seizures usually last up to a couple of minutes.
  • Quick, brief, jerky movements. Myoclonic seizures cause a quick, jerky movement. These usually only happen for just a couple of seconds but sometimes can last longer. People without seizure disorders experience something similar known as myoclonic jerks. Examples of myoclonic jerks include when you have hiccups or when you have a sudden muscle twitch that wakes you up as you’re falling asleep.
  • Sensory, psychological or other symptoms. Partial or focal seizures affect parts of your body in limited ways. You can read more on the "Epilepsy types and their symptoms" page under the “Partial epilepsy classifications” heading.


What causes the condition?

Lennox-Gastaut syndrome can happen for multiple reasons. Some of the causes happen before a person’s birth. Others happen because of events in early childhood. In about one-fourth of LGS cases, there’s no identifiable cause.

Examples of identified causes include:

Researchers have also identified “de novo” mutations that are more likely to happen in people with LGS. De novo (which means “from the beginning”) mutations are spontaneous errors in a person’s DNA. That means the mutation happened because of a DNA error in either the sperm or egg they developed from, but it wasn't an error from either parent’s DNA.

However, genetics may still play a role in whether or not a person develops this condition. As many as 30% of people with LGS have a family history of epilepsy. However, more research is necessary to show what role genetics play in this condition.

Is it contagious?

Lennox-Gastaut syndrome is not contagious, and one person can’t pass it to another. Some contagious infections can cause brain damage that leads to LGS, but these infections aren’t guaranteed causes.

Diagnosis and Tests

How is Lennox- Gastaut syndrome diagnosed?

Diagnosing LGS usually takes a combination of diagnostic testing and a healthcare provider doing a neurological exam. A pediatrician may suspect this condition based on parents’ reports of their child’s symptoms, especially if the child also has learning difficulties or problems with behavior.

What tests will be done to diagnose this condition?

The most common tests used to diagnose LGS include:

  • Electroencephalogram (EEG). This test uses several electrodes attached to a person’s head with a sticky, conductive gel. That gel makes the brain's electrical activity easier to detect. EEGs are particularly useful in diagnosing LGS, which causes a distinctive type of electrical pattern in a person’s brainwaves.
  • Magnetic resonance imaging (MRI). This test uses an extremely powerful magnet and computer processing to generate a high-resolution picture of the inside of the body, especially the brain. This test is especially helpful in spotting brain development problems.
  • Lab testing. These tests will analyze blood and urine, looking for potential seizure activity causes. Some of the things analyzed include blood chemistry, liver enzymes and kidney function. While many of these tests can't help diagnose LGS itself, they can help rule out other problems that look like LGS.
  • Genetic testing. This test can identify if a person has any hereditary conditions that could cause LGS. It can also identify any spontaneous mutations that might cause LGS.

There are other possible tests that a person might also undergo to rule out similar conditions. A healthcare provider can explain more about other possible tests and answer any questions you might have about them.

Management and Treatment

How is it treated, and is there a cure?

There are several treatment options for LGS, but this condition has a reputation as being extremely difficult to treat. In many cases, treatment involves one or even a combination of the following:


Lennox-Gastaut syndrome commonly resists medication treatments, which is what makes this condition so difficult to manage. In many cases, multiple medications are necessary. A complicating factor is that some antiseizure medications that limit certain types of seizures may increase how often other kinds happen.

When this condition resists treatments, healthcare providers may try to focus the treatment options on preventing certain types of seizures or reducing how often they happen. Preventing atonic seizures, for example, is especially important because these create a danger of fall injuries.

Dietary therapies

For many people with severe epilepsy, diet changes can help limit the frequency of seizures or stop them entirely. The ketogenic diet for epilepsy, which focuses on high protein and fat intake while avoiding carbohydrates, is one that providers often recommend. This can be an option when medication treatments haven’t worked.

While the ketogenic diet is gaining a reputation in treating severe epilepsy, it does have a few drawbacks. This diet only works when followed closely. That’s because taking in too many carbohydrates (found in sugary and starchy foods) can cause a return of seizures. However, other similar diets also might help, and a healthcare provider can help you learn about and try one of the modified diets if you choose.

Brain surgery and implanted devices

In some cases, especially when other treatment attempts don’t succeed, surgery may be the best option. Examples of these kinds of procedures include:

  • Vagus nerve stimulation. This procedure involves implanting a device that delivers a mild electrical current to the 10th cranial nerve, the vagus nerve, which connects directly to the brain. That current can reduce how often seizures happen and their severity. This effect also gets stronger over time, which means fewer and less-severe seizures. Implanting this device is often considered before more advanced surgeries because it’s a reversible procedure with fewer risks and an easier recovery time.
  • Corpus callosotomy (pronounced “corp-us cal-oh-sot-oh-me”). The corpus callosum is a part of the brain that acts as a bridge between the brain's left and right sides (hemispheres). Disconnecting the corpus callosum stops it from transmitting faulty signals, like those that happen with seizures, back and forth. This can reduce the frequency of these seizures or even stop disabling seizures entirely.
  • Hemispherectomy. This involves surgically removing one side of the brain. While that might seem extreme, experts still might use it to stop uncontrollable seizures. Later physical therapy can help a person’s brain adapt to this change in many cases. The brain will also remap itself, so the remaining half takes over the jobs of the removed half.
  • Resection. Structural anomalies in the brain can sometimes cause LGS. If healthcare providers can find an anomaly, they might be able to remove the damaged or diseased brain tissue to stop the seizures. Unfortunately, this usually isn't an option with LGS because the seizure activity involves more than one area of the brain, making this less likely to work.

Complications/side effects of the treatment

The complications of the treatments are specific to the treatments involved. Because of that, you should talk to a healthcare provider about the specific complications and side effects of the treatments that will affect you or your loved one. The provider can best tailor that information to your particular situation, including your circumstances, other conditions involved, and more.

How soon after treatment will I feel better, and how long does it take to recover?

The time it takes to recover after treatment depends very strongly on the treatments used and the overall situation. A healthcare provider is the best person to explain what to expect and the likely timeline for recovery.


How can I prevent Lennox-Gastaut syndrome?

In many cases, LGS is not a preventable condition, and it's not possible to reduce your risk of it happening. The exception is the prevention of head and brain injuries that can lead to LGS. Ensuring that your children use approved, certified helmets is the only way to avoid this condition happening because of injuries.

Outlook / Prognosis

What can I expect if my child or I have this condition?

Lennox-Gastaut syndrome is a condition that usually has severe impacts. Most children with this condition will have learning difficulties and permanent brain damage that limits their mental abilities. Children with this also have a higher risk of injuries from falls because atonic seizures (drop attacks) are so common and lead to falls.

This condition is also difficult to treat. Most children with this condition need lifelong skilled medical care because they can’t care for themselves alone. However, some people with this condition only have minimal brain damage, which means they can live independently.

How long does Lennox-Gastaut syndrome last?

Unless treated in a way that stops seizures entirely, which is rare, LGS is a lifelong condition.

What’s the outlook for this condition?

The biggest risks from Lennox-Gastaut syndrome come from damage to the brain due to uncontrolled seizures or falls that happen because of seizures. Because of those risks, people with LGS have a death rate between 3% and 7% over 10 years after their diagnosis.

In some cases, medical procedures can stop seizures from LGS. That stops this condition but cannot undo any brain damage from earlier seizures.

Living With

How do I take care of myself?

If you or a loved one has LGS, it’s important to follow your healthcare provider’s guidance on how to take care of yourself. That includes the following:

  • Taking medication as prescribed.
  • Seeing your healthcare provider as recommended.
  • Monitoring seizures and avoiding any potential triggers or situations that might make seizures happen.

When should I see my healthcare provider?

You or your child’s healthcare provider will recommend regular visits as needed. You should also see your healthcare provider if the seizure symptoms change in any way that's noticeable or affects your usual routine and activities.

When should I go to ER?

You should go to the nearest hospital emergency room if you or your child has one or more seizures that meet the definition of status epilepticus, which is a medical emergency. That is when one or more seizures meets the following criteria:

  • One seizure that lasts for between five and 30 minutes.
  • Two or more seizures that happen within 30 minutes, without the person recovering fully between seizures.

A note from Cleveland Clinic

Lennox-Gastaut syndrome is a rare type of severe childhood epilepsy. It usually has severe impacts on a child’s life, many of which are permanent and last into adulthood. While this condition is difficult to treat, newer medications, procedures and treatment methods can help ease the severity of this condition and limit how it progresses. In uncommon cases, treatments can provide complete remission of this condition entirely. However, more research is necessary before this condition is truly treatable or curable.

Medically Reviewed

Last reviewed on 06/02/2022.

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