Lennox-Gastaut Syndrome (LGS)

Lennox-Gastaut syndrome (LGS) is a severe form of childhood epilepsy characterized by a triad of symptoms, including multiple seizure types, diffuse slow spike-and-wave patterns on electroencephalography (EEG), and cognitive impairments that are often severe.1 The seizures experienced by patients with LGS are often resistant to antiseizure medication (ASM) therapy.1,2 

Combination ASM therapy attempts to manage a patient’s types of seizures, however, as these seizures are progressive in type, frequency, and severity, this is a complex task. Also, some ASMs can work for one type of seizure but worsen another type. 1

Factors Affecting Life Expectancy of LGS

Because of the refractory nature of most seizures in LGS, overall prognosis remains poor for individuals with this disease. Outcomes for seizure control and cognitive impairment are often worse in individuals with a history of infantile spasms and West syndrome as the causation of LGS.1 According to the LGS Foundation, approximately 80% to 90% of children with LGS continue to have seizures into adulthood on account of resistance to antiepileptic treatments.3

It’s often important for providers to focus on controlling a patient’s atonic and tonic seizures, due to the risks of injury and mortality that accompany them. Life expectancy greatly depends on the patient’s degree of seizure control, especially atonic and tonic seizures, as this affects the patient’s exposure to further brain damage, accidental injury, status epilepticus, unexpected death, and progressive cognitive and behavioral impairment.1

The overall mortality rate for LGS is 5%. Patients with LGS are 24 times more likely to die prematurely, usually a result of seizures, sudden unexpected death in epilepsy (SUDEP), accidents, or the patient’s underlying brain disorder.3

Read more about LGS prognosis 

Mortality Risk Due to Brain Injuries and Permanent Neurological Damage 

Intractable seizures can be dangerous and a risk to mortality. Cumulative brain damage can occur during frequent episodes, and traumatic head injuries can occur from falls during loss of muscle control in certain types of seizures, including atonic drop attacks. It is estimated that the risk of mortality due to brain injuries incurred during seizures in patients with LGS ranges from 3% to 7% during a 8- to 10-year follow-up period after initial diagnosis.1,2 

Another concern in patients with LGS is status epilepticus, which is classified as a medical emergency due to the possibility of permanent brain damage and death. Patients with LGS experiencing one seizure lasting longer than 5 minutes and up to 30 minutes or 2 or more seizures within a 30-minute period, which prevents full recovery between seizures, require immediate transport to the emergency department.2 

Another potential complication that may occur is the aspiration of saliva during a seizure, which may progress to aspiration pneumonia. Depending on the severity of infection, this may increase the risk of mortality.4

Read more about LGS complications

Sudden Unexpected Death in Epilepsy

Sudden unexpected death in epilepsy is the sudden and unexpected death of an individual with epilepsy who is otherwise healthy and may or may not have experienced a convulsive seizure directly prior to death. Autopsies often cannot clarify cause of death, and research is still unclear about what may cause SUDEP.5 However, it seems SUDEP may occur more frequently in individuals with LGS, possibly because their seizures are often difficult to control with medications.1,6 

One study that analyzed mortality rates in various types of new-onset childhood epilepsies indicated that, on average, deaths occurred around 7.5 years following diagnosis, with a notable trend that individuals whose epilepsy manifested later demonstrated longer lengths of time until death.6

Lennox-Gastaut syndrome commonly manifests between the ages of 2 and 5 years, sometimes earlier, thus increasing the risk of SUDEP. In this study of 69 children with new-onset epilepsy, 13 individuals had a diagnosis of either West syndrome, LGS, or Ohtahara syndrome, and 3 of these patients died of SUDEP. The risk of SUDEP increased with an increased number of annual seizures, status epilepticus, convulsions, and drug resistance.6

The LGS Foundation reported that premature death in patients with LGS is commonly due to SUDEP.3

Read more about LGS comorbidities

Risk of Accidents in Lennox-Gastaut Syndrome

Individuals with LGS demonstrate an increased risk of accidents that may lead to premature death.3 Severe cognitive impairment and behavioral problems may increase the risk of accidents and premature death, including a lack of safety awareness,7 inattention, hyperactivity, rage attacks, and aggression.5

Read more about LGS risk factors

Studies on Life Expectancy in LGS

One study followed 38 individuals, aged 18 years and over, with a diagnosis of LGS for a median of 14 years. By the end of the longitudinal study, the researchers reported that at the time of the last documented assessment, the average age was 43.3±10.6 years, indicating that it is possible for individuals with LGS to survive into their 50s.8 The LGS Foundation reports an even longer survival, with individuals into their 50s and sometimes even their 60s.4

Another longitudinal study, with an average follow-up duration of 19 years, analyzed long-term prognosis in 68 adults between the ages of 18 and 35 years with LGS. The researchers reported that a ketogenic diet and epilepsy surgery improved seizure control in this patient population. However, these treatments did not necessarily result in a completely seizure-free state, and nothing was specifically mentioned about the impact of these treatments on life expectancy.9

Read more about LGS treatment


  1. Amrutkar C, Riel-Romero RM. Lennox Gastaut syndrome. In: StatPearls [Internet]. Treasure Island, FL: StatPearls Publishing; 2022. Updated August 1, 2022. Accessed February 14, 2023.
  2. Lennox-Gastaut syndrome (LGS). Cleveland Clinic. Accessed February 14, 2023.
  3. Lennox-Gastaut syndrome. LGS Foundation. Accessed February 14, 2023.
  4. Ajinkya S, Wirrell E. What is Lennox-Gastaut syndrome? LGS Foundation. Updated December 21, 2022. Accessed February 14, 2023. 
  5. SUDEP. Epilepsy Foundation. August 5, 2013. Updated March 29, 2022. Accessed February 14, 2023. 
  6. Berg AT, Nickels K, Wirrell EC, et al. Mortality risks in new-onset childhood epilepsy. Pediatrics. 2013;132(1):124-131. doi:10.1542/peds.2012-3998
  7. Seizures & safety. LGS Foundation. Accessed February 14, 2023.
  8. Vignoli A, Oggioni G, De Maria G, et al. Lennox–Gastaut syndrome in adulthood: long-term clinical follow-up of 38 patients and analysis of their recorded seizures. Epilepsy Behav. 2017;77:73-78. doi:10.1016/j.yebeh.2017.09.006
  9. Kim HJ, Kim HD, Lee JS, Heo K, Kim DS, Kang HC. Long-term prognosis of patients with Lennox–Gastaut syndrome in recent decades. Epilepsy Res. 2015;110:10-19. doi:10.1016/j.eplepsyres.2014.11.004

Reviewed by Michael Nace, on 2/27/2023.