What causes Lennox-Gastaut syndrome?

There are many possible causes of Lennox Gastaut Syndrome (LGS). These causes are divided into one of two groups, that fall into one of two groups, symptomatic or cryptogenic.

The symptomatic group means that something can be identified as a cause of the epilepsy, usually something that has caused a more diffuse brain injury (an injury affecting large areas of the brain). Examples of symptomatic causes include infections of the brain tissue (encephalitis) or the covering of the brain (meningitis), tuberous sclerosis complex, brain malformations, injury at birth (causing decreased blood and oxygen to the brain), trauma, and injuries to the frontal lobes of the brain.  About 75% of people with LGS have a symptomatic or identifiable cause.

The cryptogenic group means that no clear cause can be demonstrated.  Some genetic studies have found mutations or changes on parts of genes that could contribute to the development of LGS in some people.  These genetic findings have very complex relationships and how much they actually contribute to LGS is not yet completely known.

Does infantile spasms or West Syndrome cause LGS?

West syndrome is a form of epilepsy that occurs in infants. Infants develop a type of seizure called infantile spasms or IS in the first year of life. The EEG of a child with IS has a distinctive pattern called hypsarrhythmia.

While West syndrome is not a specific cause of LGS, it has been shown that up to 30% of children who develop LGS have a history of infantile spasms or West syndrome.  A review of published studies found that 20% of children with LGS had infantile spasms when they were younger. One study completed in Nova Scotia, Canada followed 692 children with epilepsy over 20 years. This study found that 1 out of 3 children with IS developed LGS over time. The researchers also found that 6.5 out of 10 people with LGS had a history of IS or West syndrome. 

People with LGS and an early history of IS or West syndrome usually have a poor outlook for seizure control and cognitive function. 

Authored By: 
Patricia O. Shafer RN, MN
Elaine Kiriakopoulos MD, MSc
Reviewed By: 
Joseph I. Sirven, MD
Reviewed Date: 
Sunday, November 23, 2014