Lennox-Gastaut syndrome (LGS) is a rare, severe form of epilepsy that usually starts in early childhood and often continues into adulthood. LGS causes different types of seizures, cognitive challenges (problems with learning or thinking), and unusual brain activity seen on an electroencephalogram (EEG). About 70 percent of LGS cases are linked to brain malformations, injuries, or infections.

LGS accounts for 3 percent to 4 percent of childhood epilepsy cases and usually starts between the ages of 2 and 5. The condition affects males slightly more frequently than females, according to StatPearls, an online medical reference written and reviewed by healthcare professionals. Some people with LGS can live independently, but most need ongoing support due to challenges with thinking, memory, and behavior.

Read on to learn more about life expectancy and outlook for people with LGS, along with symptoms, types of seizures, and other key information.

Lennox-Gastaut Syndrome Prognosis

LGS is part of a group of disorders called epileptic encephalopathies. These conditions involve ongoing seizures along with worsening developmental delays, trouble with thinking and learning, and behavioral issues over time. LGS can be hard to treat because it doesn’t respond well to many anti-seizure medications (ASMs). Early diagnosis and aggressive treatment that focuses on seizure control and neurodevelopmental support can help improve outcomes.

More than two-thirds of people with Lennox-Gastaut syndrome experience status epilepticus.

This chronic condition has no cure, and complete recovery is not expected. People with LGS have a death rate 14 times higher than that of the general population. This higher rate is largely due to seizure-related complications, including status epilepticus and sudden unexpected death in epilepsy (SUDEP), as well as complications related to intellectual and physical disabilities.

Lennox-Gastaut Syndrome Symptoms and Seizures

People with LGS often have more than one type of epileptic seizure, including those described below. In many cases, intellectual disabilities or developmental delays appear early in life.

LGS Behavioral Problems and Developmental Issues

Most children with LGS have developmental and cognitive impairments, including intellectual disabilities or learning problems, even before seizures start. These issues may worsen over time, particularly if seizures are frequent or severe. In a study that followed children with LGS for 17 years, up to 99 percent of participants developed intellectual disabilities. Many also had delayed development of motor skills, such as sitting and crawling. Behavioral problems, such as hyperactivity and aggression, were seen in half of the participants.

Most children with LGS continue to have seizures as adults. Due to ongoing developmental and behavioral challenges, many people with LGS need help with daily activities throughout their lives.

Tonic Seizures

Most people with LGS experience tonic seizures, which cause sudden, uncontrollable muscle stiffening. Tonic seizures usually last about 20 seconds and happen during sleep. If a seizure occurs while a person is awake, they might fall suddenly and feel tired or confused afterward.

Atonic Seizures

People with LGS may have atonic seizures, sometimes called drop attacks. During an atonic seizure, a person loses muscle tone, causing them to go limp and fall. To reduce the risk of head injury, some people may need to wear a helmet or other protective gear.

Atypical Absence Seizures

Also seen in LGS, atypical absence seizures involve brief staring spells and may include subtle movements such as blinking or nodding. These seizures can look similar to inattention or daydreaming. People usually don’t remember these seizures afterward.

Focal Seizures

Focal seizures are also common in people with LGS. These seizures start in one area of the brain and can cause unusual sensations, movements, or changes in awareness, depending on the part of the brain involved.

Myoclonic Seizures

Myoclonic seizures are less common in LGS but can still occur. These seizures cause brief muscle jerks, like electric shocks, that happen one at a time or in clusters.

Tonic-Clonic Seizures

Tonic-clonic seizures include two separate phases. During the tonic phase, the body stiffens. During the clonic phase, the muscles jerk rhythmically. People usually lose consciousness during these seizures and feel confused or very tired afterward.

Infantile Spasms

Some children who later develop LGS have infantile spasms, also called infantile epileptic spasms syndrome. The condition was previously known as West syndrome. Infantile spasms involve sudden, involuntary movements, such as jerking the head, neck, and torso or stiffening the legs and arms. The spasms often occur in clusters and may be linked to developmental issues.

Status Epilepticus

Status epilepticus, a serious complication of LGS, is defined as seizures that last longer than five minutes or happen so close together that the person doesn’t recover in between. This condition is life-threatening and requires emergency medical care.

There are two main types of status epilepticus — convulsive, which causes jerking and stiffness, and nonconvulsive, which affects awareness without noticeable movements. Both types, especially when they last a long time or happen often, are linked to worsening mental decline over time. More than two-thirds of people with LGS experience status epilepticus at some point.

Status epilepticus raises the risk of brain damage, injury, and other serious consequences, so rapid medical treatment is critical. Frequent episodes of status epilepticus play a major role in reduced quality of life and higher mortality in people with LGS.

The Importance of Controlling Seizures

Drop attacks are among the most disabling seizures for people with LGS. These seizures can cause repeated falls, leading to frequent injuries and increasing disability over time. Poorly controlled seizures also increase the risk of SUDEP.

The most effective way to lower the risk of injury, status epilepticus, or SUDEP is to control seizures as much as possible. Doctors create treatment plans based on each person’s needs. Treatment options may include anti-seizure medications, dietary therapy, or alternative approaches.

In addition to general anti-seizure medications, drugs from several ASM classes have been approved by the U.S. Food and Drug Administration (FDA) to treat LGS. These medications include:

• Benzodiazepines, such as clobazam
• Cannabinoids, such as cannabidiol
• Carbonic anhydrase inhibitors, such as topiramate
• Dicarbamates, such as felbamate
• Phenyltriazines, such as lamotrigine
• Serotonin-modulating medications, such as fenfluramine

Diagnosis of Lennox-Gastaut Syndrome

LGS is diagnosed based on specific symptoms, including:

• Multiple seizure types, often including tonic seizures during sleep
• A distinct brain wave pattern on EEG called slow spike-and-wave
• Cognitive, developmental, or behavioral challenges that often get worse over time

Healthcare providers diagnose LGS after doing a physical exam, reviewing medical history, and ordering tests to evaluate brain activity. An EEG is usually done to measure the brain’s electrical activity and look for seizure patterns. Doctors might also order magnetic resonance imaging (MRI) to create detailed images of the brain and help identify the cause of the seizures.

In 70 percent to 80 percent of people with Lennox-Gastaut syndrome, the disease has an identifiable cause.

It can take several years to correctly diagnose LGS. Delays often happen because LGS shares features with other types of epilepsy, and its defining signs may not be apparent when seizures first begin.​

Causes of Lennox-Gastaut Syndrome

In many cases, LGS has an identifiable cause, but estimates vary across studies. Some sources report an identifiable underlying cause in about 70 percent to 80 percent of cases, while others estimate that up to 40 percent of cases have no identifiable cause. Causes and contributing factors can include the following:

• Brain injury or developmental problems — When part of the brain has developed abnormally (also called a brain malformation) or is injured, it’s more likely to cause seizures.
• Genetic disorders — Most people with LGS don’t have a family history of the condition. However, a family history of epilepsy has been reported in 3 percent to 30 percent of people with LGS.
• Other epilepsy syndromes — LGS can also develop from other epilepsy syndromes, such as infantile spasms or Ohtahara syndrome.
• Unknown cause — In some cases, the cause of LGS can’t be identified.

Talk With Your Doctor

LGS is a serious, lifelong form of epilepsy that affects thinking, behavior, and daily living. Because LGS involves multiple seizure types and developmental challenges, staying informed can help individuals and families better navigate its effects. As a caregiver, if you have questions about how LGS might affect your loved one, talk with a neurologist experienced in treating the syndrome.

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