EEG findings in Lennox-Gastaut syndrome: Pursuing a moving target

Lennox-Gastaut Syndrome (LGS) is a life-long, drug-resistant developmental epileptic encephalopathy (DEE) that develops in young children between 18 and 24 months of age and up to 18 years of age. The overall incidence is estimated at 0.1 to 0.28 per 100,000 people per year and a lifetime prevalence at age 10 of about 0.26 per 1,000 children. LGS accounts for 1-2 % of all epilepsy cases and 2-5 % of childhood epilepsies, with a higher ratio of males. The disruption of LGS on the lives of patients and their caretakers is considerable given its chronic nature, the injury from the seizures, the need for a high degree of medical supervision, and the toll the syndrome takes on the patients' cognitive and neurologic development. There is variability in the literature on the overall incidence of LGS due to changes in the definitions in past classifications regarding age of inclusion, mandatory seizure types, and mandatory EEG findings. This review focuses on the evolution of the ictal and interictal EEG findings over the course of the syndrome and the developing nature of the seizure types.