Lennox-Gastaut Syndrome (LGS)

Lennox-Gastaut syndrome (LGS) is a severe form of epilepsy that typically manifests in early childhood. Affected individuals present with 3 characteristic clinical features: multiple and diverse types of seizures, a specific brain wave pattern on electroencephalography (EEG) called the slow spike-and-wave, and cognitive impairment.1 

Incidence and Prevalence of LGS

Lennox-Gastaut syndrome accounts for approximately 1% to 2% of all epilepsy cases and between 2% and 5% of all childhood epilepsies.2,3 LGS causes around 10% of cases of epilepsy occurring before the age of 5 years.3

The incidence of LGS is estimated at around 0.7% of newly diagnosed childhood cases of epilepsy annually.2 This number was obtained from the average incidence rates reported in 3 different studies published between 1998 and 2007 that documented how many children with newly diagnosed epilepsy had LGS.4-6 

In the most recent study published in 2007, 4 out of 692 (0.5%) children with newly diagnosed epilepsy had LGS.4 In the second study conducted by Berg and colleagues, 4 out of 613 (0.65%) children with newly diagnosed epilepsy had LGS.5 In the third study, Callenbach and colleagues calculated the incidence of LGS among Dutch children, reporting that 4 out of 462 (0.9%) children with newly diagnosed epilepsy had LGS.6

The global prevalence of LGS ranges from 1 to 5 cases per every 10,000 people.7 It is estimated that around 1 million individuals worldwide have LGS.2

Read more about LGS signs and symptoms

The Effect of Disease Progression on LGS Incidence

It must be noted that over time, the incidence of LGS increases among patient populations due to the evolution of other epileptic syndromes into LGS.2 

For example, in the Berg et al study, 4 children initially received an LGS diagnosis at the start of the study, at an incidence rate of 0.65%. After an additional 2-year follow-up period, 19 children were diagnosed with LGS, with 13 cases evolving from West syndrome and other conditions of unknown etiology. With time progression, the final incidence rate increased to 3.1%.5 

In the Camfield and Camfield study, 17 children were diagnosed with LGS, including 11 evolutions from West syndrome.4

Read more about LGS etiology

Geographical Factors of LGS

Most epidemiological studies for LGS were published in the late 1990s and early 2000s. The most recent study on LGS prevalence was published in 2021. 

Epidemiology of LGS in the United States

In the United States, around 29,000 cases of childhood epilepsy are diagnosed annually. With an initial incidence rate of 0.7%, around 200 of these children are diagnosed annually with LGS. The prevalence of LGS in the United States is estimated at up to 47,800 total cases.2 

In a study conducted in 1997 in Atlanta, Georgia, the lifetime prevalence of LGS by 10 years of age was 26 cases per every 100,000 people.8 

Read more about LGS diagnosis

Epidemiology of LGS in Iran

During a 5-year period between 2008 and 2012, 135 out of 2500 (5.4%) patients with epilepsy at Shiraz University of Medical Sciences in southern Iran were diagnosed with LGS.9 

Epidemiology of LGS in the Netherlands

Lennox-Gastaut syndrome occurred at an incidence of 0.9% in a population of 462 children in a Dutch study.6

Epidemiology of LGS in Finland

Researchers published a study in 1997 that retrospectively analyzed the annual incidence of LGS in children between the ages of 0 and 14 years from 1975 and 1985. They calculated the annual incidence of LGS at around 2 cases in every 100,000 children in this age group.10

Epidemiology of LGS in the United Kingdom

In the United Kingdom, the prevalence of patients with LGS, as seen in primary care settings, was around 0.578 cases in every 10,000 patients. In this study, 74 patients had confirmed LGS and 106 had probable LGS.11

Read more about LGS clinical features

Race/Ethnicity Factors of LGS

No studies have reported any racial or ethnic predispositions for developing LGS.3 The condition affects people of all races and ethnicities.12

Sex Factors of LGS

According to the study from Iran, LGS occurs more commonly in male patients than female patients.3,9 Out of 135 children with LGS, 83 (61.5%) were male and 52 (38.5%) were female.9

Read more about LGS risk factors

Age Factors of LGS

The onset of LGS usually occurs in children between the ages of 2 and 5 years. Most children are diagnosed before 6 years of age. Some cases occur in neonates. According to medical reports, the oldest individual with LGS survived until 50 years of age; however, the risk of disease-related mortality increases with age.2

Read more about LGS life expectancy


  1. Lennox-Gastaut syndrome. MedlinePlus. Updated September 14, 2022. Accessed February 13, 2023.
  2. How many people have LGS? LGS Foundation. Updated August 22, 2022. Accessed February 13, 2023.
  3. Amrutkar C, Riel-Romero RM. Lennox Gastaut syndrome. In: StatPearls [Internet]. Treasure Island, FL: StatPearls Publishing; 2022. Updated August 1, 2022. Accessed February 13, 2023.
  4. Camfield P, Camfield C. Long-term prognosis for symptomatic (secondarily) generalized epilepsies: a population-based study. Epilepsia. 2007;48(6):1128-1132. doi:10.1111/j.1528-1167.2007.01072.x
  5. Berg AT, Shinnar S, Levy SR, Testa FM, Smith-Rapaport S, Beckerman B. How well can epilepsy syndromes be identified at diagnosis? A reassessment 2 years after initial diagnosis. Epilepsia. 2000;41(10):1269-1275. doi:10.1111/j.1528-1157.2000.tb04604.x
  6. Callenbach PM, Geerts AT, Arts WF, et al. Familial occurrence of epilepsy in children with newly diagnosed multiple seizures: Dutch study of epilepsy in childhood. Epilepsia. 1998;39(3):331-336. doi:10.1111/j.1528-1157.1998.tb01382.x 
  7. Lennox-Gastaut syndrome. Orphanet. Updated April 2021. Accessed February 13, 2023.
  8. Trevathan E, Murphy CC, Yeargin-Allsopp M. Prevalence and descriptive epidemiology of Lennox-Gastaut syndrome among Atlanta children. Epilepsia. 1997;38(12):1283-1288. doi:10.1111/j.1528-1157.1997.tb00065.x
  9. Asadi-Pooya AA, Sharifzade M. Lennox-Gastaut syndrome in south Iran: electro-clinical manifestations. Seizure. 2012;21(10):760-763. doi:10.1016/j.seizure.2012.08.003
  10. Heiskala H. Community-based study of Lennox-Gastaut syndrome. Epilepsia. 1997;38(5):526-531. doi:10.1111/j.1528-1157.1997.tb01136.x
  11. Chin RFM, Pickrell WO, Guelfucci F, Martin M, Holland R. Prevalence, healthcare resource utilization and mortality of Lennox-Gastaut syndrome: retrospective linkage cohort study. Seizure. 2021;91:159-166. doi:10.1016/j.seizure.2021.05.025
  12. What is LGS? Onfi®. Accessed February 13, 2023.

Reviewed by Harshi Dhingra, MA, on 2/13/2023.