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Epilepsy Health Center

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Lennox-Gastaut Syndrome

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What Is Lennox-Gastaut Syndrome?

Lennox-Gastaut syndrome (LGS) is a rare and severe kind of epilepsy that starts in childhood. Children with LGS have seizures often, and they have several different kinds of seizures.

This condition is hard to treat, but researchers are looking for new therapies. Finding practical and emotional support is key to help you give your child the best quality of life while facing the challenges and stress this illness brings.

The seizures usually start between ages 2 and 6. Children with LGS have learning difficulties and developmental delays (like sitting, crawling, walking) that can be moderate to severe. They can also have behavioral problems.

Each child develops differently, and it's impossible to predict how a child with LGS will do. While most children have ongoing seizures and some form of learning disability, some may respond well to treatment and have fewer seizures.

Others may continue to have seizures often, as well as problems with thinking, development, and behavior, and will need help with daily living activities. Some parents find that a special diet, called the ketogenic diet, helps.


Doctors don't always know what caused a child's LGS. In some cases, it could be caused by:

  • Lack of oxygen during birth
  • Severe brain injuries linked with pregnancy or birth, such as low birth weight or premature birth
  • Brain infections (such as encephalitis, meningitis, or rubella)
  • Seizures that start in infancy, called infantile spasms or West’s syndrome
  • A brain problem called cortical dysplasia, where some nerve fibers in the brain don’t line up right during development in the womb
  • Tuberous sclerosis, where non-cancerous tumors form in many places throughout the body, including the brain


Children with LGS have frequent and severe seizures. And they often have different kinds of seizures, including:

Atonic seizures. Also called "drop attacks," because the person loses muscle tone and can fall to the ground. Their muscles may jerk. These seizures are brief, usually lasting a few seconds.

Tonic seizures. These seizures cause the person's body to stiffen and can last for a few seconds to a minute. They usually happen when the person is asleep. If they happen when the person is awake, they can cause falls. Like atonic seizures, they are also called drop attacks.

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