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What is LGS?

  • Lennox-Gastaut Syndrome (LGS) is a rare epilepsy syndrome.

  • Nobody is born with LGS. It may develop over time from childhood seizures that remain uncontrolled by treatments.

  • Children and Adults with LGS share similar features:

    • Seizures that start in childhood

    • More than one seizure type

    • Slow spike-and-wave on EEG

    • Developmental delay/cognitive impairment (70% have this at diagnosis of LGS)

  • Any seizure type can be seen in LGS. The most common seizure types are:

    • Tonic

    • Atonic Drop Seizures

    • Generalized Tonic-Clonic

    • Atypical Absence

    • Non-convulsive status epilepticus

    • Myoclonic

  • While developmental delay/cognitive impairment occurs in most with LGS, it is not always present at the start of LGS and is not required for the diagnosis to be made.

What causes LGS?


  • LGS occurs secondary to many different causes including injury, brain malformations, infections, and genetic factors.

  • Most with LGS may have abnormal brain imaging, but some have normal brain imaging prior to developing LGS.

  • LGS can also develop from other epilepsy syndromes such as West, Ohtahara, Hypothalamic Hamartoma, etc.

  • Many genes are associated with LGS and each gene is a risk factor for developing LGS if seizures remain uncontrolled.

  • Emerging evidence suggests that genetic factors account for most unknown causes of LGS.


Who has LGS?

  • 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.

  • This means approximately 48,000 children and adults in the United States currently have LGS.

  • Click here for more information on the epidemiology of LGS. 

How does LGS change over time?

  • There is no cure for LGS. Seizures may go into remission, and may also recur.

  • 30-50% of children with infantile spasms will develop LGS.

  • 80-90% of children with LGS will continue to have seizures into adulthood.

  • Up to 70% with LGS will no longer show slow spike-and-wave (<3Hz) on EEG in adulthood.

  • Most with LGS show paroxysmal fast rhythms (10-20 Hz) on EEG, mainly during non-REM sleep, at some point in their life.

  • 70% with LGS will show cognitive impairment at diagnosis and more than 50% suffer behavioral issues including hyperactivity, sleep disturbances, rage attacks, aggression, and autistic features.

  • The mortality rate is 5%. Those with LGS are 24 times more likely to die prematurely.

  • Premature death in LGS is often due to Sudden Unexpected Death in Epilepsy (SUDEP), seizures, injury, or the underlying brain disorder.



More about LGS:


Adults with LGS:

  • As children with Lennox-Gastaut Syndrome grow older, types of seizures may change. Nearly all adults with LGS have tonic seizures (GPFA on EEG).

  • Older children with LGS often experience acute psychotic episodes, forms of psychosis with aggressiveness, behavioral problems, and irritability.

  • Cognitive issues in adults include slowed reaction time and information processing.

  • More information on adults with Lennox-Gastaut Syndrome including the process of transitioning can be found on our adults page

School-age Children:

  • School-age children are usually placed into a special education classroom or will receive home tutoring.

  • Parents and caregivers may need to consider future options for their child, including legal guardianship, respite care, group home facilities, and/or day programs.

  • For those individuals with LGS who do not have adequate neurological services in their state of residency, an out-of-state facility is suggested.

  • Level 4 facilities (facilities which provide intensive neurological services, elaborate evaluations and treatment options) are typically recommended if the local neurologist or epileptologist does not have experience in treating Lennox-Gastaut Syndrome.

  • For a listing of epilepsy centers in the United States, visit the National Association of Epilepsy Centers


  • The prognosis of Lennox-Gastaut Syndrome can greatly vary from person to person. Complete recovery, with freedom of seizures and normal development, is unusual for a child with LGS. Although there is no cure, there are various treatment options available which can be further explored on our treatments page.

Arzimanoglou A, et al. Epileptic Disord. 2011;13(Suppl 1):S3-S13.

Berg AT, et al. Epilepsia, 2018;59(11).

Bourgeois BF, et al. Epilepsia, 2014;55(Suppl 4).

Cross JH, et al. Front Neurol. 2017;8:505.

Goldsmith IL, et al. Epilepsia, 2000;41(4).

LGS Foundation Caregiver Concerns Survey 2018.

McTague A, et al. Lancet Neurol. 2016;15(3).