Page Summary

  • Lennox-Gastaut Syndrome (LGS) is a type of childhood epilepsy with multiple different types of seizures.
  • In about a quarter of children, no cause can be found. 
  • Accounts for about 2 to 5 percent of childhood epilepsies.
  • Usually LGS persists through childhood and adolescence to adult years.
  • Intellectual development is usually, but not always, impaired.
  • EEG is an essential part of the medical evaluation and brain imaging with MRI can help look for a possible cause. 
  • While seizures usually don't respond to seizure medications, treatments such as dietary therapies, implanted devices and surgery can offer hope and help for people with LGS.

What is Lennox-Gastaut syndrome?

Lennox-Gastaut Syndrome was first defined by Dr. Henri Gastaut in France in 1966 as a very severe form of childhood epilepsy, with certain common features. Dr. William G. Lennox in Boston described features of the EEG in this condition. The syndrome is named after the work of these two famous neurologists. 

This syndrome, also called LGS, has multiple types of seizures, including tonic (stiffening) and atonic (drop) seizures. Other types of generalized seizures are usually seen such as absence, myoclonic, and tonic clonic seizures. Focal or partial seizures may also occur in a person with LGS.

The EEG when a person is awake shows characteristic patterns of background slowing and diffuse spike-wave bursts. The EEG during a seizure can show many different features. 

Intellectual development is usually delayed or declines over time and behavioral problems may occur.

The term “epileptic encephalopathy” is used to describe this type of epilepsy. This suggests that the frequent seizures and abnormal EEG activity that is seen between seizures can lead to or be associated with cognitive and behavioral problems.

There are many underlying causes of this condition. In 1 out of 4 children with LGS, no cause can be identified.

Seizures associated with LGS unfortunately do not respond well to seizure medications. Treatments such as dietary therapy or devices may be helpful when used with seizure medications. A type of surgery called corpus callosotomy can help reduce atonic seizures, but is not as helpful for other seizure types seen in LGS. This type of surgery does not cure seizures with LGS. 

How common is LGS?

Lennox-Gastaut Syndrome (LGS) is a rare form of childhood epilepsy. It accounts for 2 to 5% of all childhood epilepsies, but 10% of children with seizures that begin prior to age 5. 

While LGS begins most often between 3 and 5 years old, it’s frequently not diagnosed until a child is older. Not all seizure types may be seen in the beginning and it often takes time to see how the child develops and if cognitive or behavioral problems seen in LGS occur.

This condition is a chronic illness, meaning that there is no cure and seizures and associated problems continue through adulthood. The long-term prognosis varies, yet overall it's felt to be unfavorable. Psychosocial needs of patients and families are important to address. Safety and educational resources are key to helping people with LGS. Research and new therapies aims to improve the outlook and quality of life for people with LGS. 

Authored by: Patricia O. Shafer RN, MN | Elaine Kiriakopoulos MD, MSc | Joseph I. Sirven MD on 11/2014

The Epilepsy Foundation would like to thank Lundbeck for their generosity in providing an unrestricted educational grant in support of the Lennox-Gastaut Syndrome section on