Epidemiology of Lennox-Gastaut Syndrome:

The figure of approximately 48,000 children and adults in the United States with LGS is explained below.

Please note the difference between newly diagnosed childhood epilepsy and diagnosis of LGS over time. 

  • LGS constitutes between 3-4% of all children with epilepsy and 1-2% of all people with epilepsy.

  • LGS typically appears between age 2-5 years of age, but can be seen in younger and older children. LGS is established in the majority of children by age 6 years of age.

  • Approximately 13,400 children under the age of 18 in the United States are estimated to have LGS.

  • Approximately 34,300 adults 18 years and older in the United States are estimated to have LGS


Previous epidemiological studies have shown the following incidence of LGS in newly diagnosed childhood epilepsy:

  • 4 individuals with LGS were diagnosed among 692 childhood epilepsy cases (0.5%) - Camfield, 2007   

  • 4 individuals with LGS were diagnosed among 462 childhood epilepsy cases (0.9%) - Callenbach, 1998   

  • 4 individuals with LGS were diagnosed among 613 childhood epilepsy cases (0.6%) - Berg, 2000   


According to these studies, then 12 people with LGS were diagnosed among 1767 cases (0.7%) of newly diagnosed childhood epilepsy.

Since there are, per the CDC, approximately 29,000 cases of childhood epilepsy diagnosed each year, 0.7% of 29,000 = about 200 children per year in the US have LGS at first diagnosis.

However, the incidence of LGS after first diagnosis of epilepsy increases over time. 

  • Camfield reported 17 LGS cases out of 692 children with epilepsy after first diagnosis (2007)

  • Berg reported 21 LGS cases out of 613 children with epilepsy at 2 years, 5 years, and 9 years after diagnosis (2000).


These figures show 38 LGS cases out of 1305 children with epilepsy, making 2.9% of childhood epilepsies LGS. This would amount to 841 children per year in the U.S. who develop LGS after initial epilepsy diagnosis. 

Trevathan (1997) published data that show that 0.26/1000 children aged 10 years and older in the Atlanta area had LGS. This translates to approximately 1,040 ten year olds in the U.S. have LGS based on population age/ data. 

What does this all mean? 

These data show that apx. 841-1040* children per year in the U.S. develop LGS over time. The LGS Foundation estimates the duration of illness from 0-50 years.**

Copyright LGS Foundation

Therefore, based on these calculations, the estimated prevalence of LGS in the United States ranges from 39,045 to 47,800 total cases (with 12,120 - 12,520 individuals under the age of 18). 


*Assumes steady state (same number of births/deaths each year, same proportion of those develop the same kinds of epilepsies, same number of children present with or convert to LGS in each year's cohort, etc.)

**The LGS Foundation realizes that many individuals with LGS live beyond 50 years of age. However, given the increased risk of mortality as the individual ages, these figures are based on a lifespan of 50 years of age. Therefore, these numbers are our best estimate at this time until further studies are done in the adult population.