Definition:

Lennox-Gastaut syndrome (LGS) is an epileptic encephalopathy characterized by multiple seizure types, typical findings in the electroencephalogram (EEG), and delayed psychomotor development. Tonic seizures during sleep are the feature often used as the foundation for diagnosis. LGS is characterized by multiple concurrent seizure types, including tonic, atypical absence seizures, atonic, and myoclonic jerks. Non-convulsive status epilepticus, lasting days to weeks, occurs in half of patients. The etiology of LGS is heterogeneous and includes both genetic and acquired causes. LGS most commonly first manifests in children between 3 and 5 years of age, but onset can also occur at younger and older ages. It has been reported that 20-36% of children diagnosed with LGS syndrome have a history of West syndrome.