The new International League Against Epilepsy (ILAE) definition of Lennox-Gastaut syndrome: Practical implications and limitations

Purpose: There are three major changes in the new definition of Lennox-Gastaut syndrome (LGS) compared with the traditional definition: (1) onset prior to 18 years, (2) must include tonic seizure, (3) generalized slow spikewaves (SSW) and (instead of or) generalized paroxysmal fast activity (GPFA) on electroencephalography (EEG). We investigated the practical implications and potential limitations of the new LGS definition based on a large cohort of patients in an exploratory study. Methods: This was a retrospective database study. All patients with an electro-clinical diagnosis of LGS (based on its traditional definition) at the outpatient epilepsy clinic at Shiraz University of Medical Sciences, Shiraz, Iran were included (from 2008 until 2020). Patients were reclassified based on the new definition of LGS. Results: In total, 3737 patients were registered. Based on its traditional definition, 300 patients were diagnosed as having LGS. According to the new definition of LGS, only 96 patients (32% of the traditional cohort) had LGS. One patient, who had other criteria, had and age at onset of 21 years; 29 patients (9.7%) did not have SSW in their EEGs; 139 people (46.3%) did not have GPFA in their EEGs; and, 111 patients (37%) did not report having tonic seizures. Conclusion: The new International League Against Epilepsy (ILAE) definition of LGS has some important practical implications and limitations. Before reinforcing and making this new definition compulsory in future research and clinical practice, more work is needed to enlighten various aspects of such changes in the definition of this epilepsy syndrome.

Automated summary

Compared to the traditional definition, the new definition of Lennox-Gastaut syndrome (LGS) has three major changes: onset prior to 18 years, inclusion of tonic seizures, and presence of generalized slow spikewaves (SSW) and/or generalized paroxysmal fast activity (GPFA) on EEG. This exploratory study examined the practical implications and potential limitations of the new LGS definition based on a large cohort of patients.