[1] Typically, it presents in children aged 3–5 years and most of the time persists into adulthood with slight changes in the electroclinical phenotype.

[4] LGS was named for neurologists William G. Lennox (Boston, US) and Henri Gastaut (Marseille, France),[5] who independently described the condition.

[7] The mainstay symptoms are seizures that are frequent – occurring daily and difficult to treat with anti-seizure medications.

[12] They present often as tonic eyelid opening with some changes in breathing coupled with pupillary dilation, urinary incontinence, increased heart rate, and flushing.

The attacks are characterized by a single, generalized myoclonic jerk that precedes tonic contraction of axial muscles.

[citation needed] Findings that strongly suggest LGS include abnormal, consistent slow spike-wave (< 3 hertz [Hz]) on awake EEG.

[citation needed] The LGS medical pathophysiology is mostly unknown, but some evidence implicates cortical hyperexcitability occurring at critical periods of brain development.

[1] Other identified causes of early life seizures include genetic disorders such as tuberous sclerosis and inherited deficiency of methylene tetrahydrofolate reductase.

[14] Progress in genome and exome sequencing is revealing that some individuals diagnosed with Lennox–Gastaut syndrome have de novo mutations in a variety of genes, including CHD2, GABRB3, ALG13 and SCN2A.

[17] A 2013 study found a high frequency of rare copy-number variations (CNVs) in adult patients with LGS or LGS-like epilepsy.

The diagnosis of LGS should be suspected in children less than 8 years old with seizures of multiple types that cannot be treated with anti-seizure medications.

[citation needed] To confirm diagnosis, awake and asleep EEG and magnetic resonance imaging (MRI) are performed.

[citation needed] The diagnosis of LGS should also be considered in adults who have childhood-onset, intractable seizures, and intellectual disability.

[29] Are the following:[citation needed] In the past, LGS patients were not eligible for surgery, as the medical community thought it to involve the whole brain as a generalized epilepsy in all cases.

Short-term ketogenic diet might be associated with nonsignificant decreases in frequency of parent-reported seizures in children with LGS.

[35] A case series study showed 50% seizure reduction reported in almost half of children with LGS after 1 year of ketogenic diet.

However, the strength of the study is challenged because it represents reports rather than scientific analysis of the clinical outcomes such as in a randomized controlled trial.

[14] According to a 1997 community-based retrospective study in the Helsinki metropolitan area and the province of Uusimaa, the annual incidence of Lennox–Gastaut was 2 in 100,000 (0.002%) from 1975 to 1985.

[13] Vigabatrin was found by Feucht et al. to be an effective add-on in patients whose seizures were not satisfactorily controlled by valproate.