Applying the ILAE diagnostic criteria for Lennox-Gastaut syndrome in the real-world setting: A multicentre retrospective cohort study.

Abstract

Lennox-Gastaut syndrome (LGS) is an archetypal developmental and epileptic encephalopathy, for which novel treatments are emerging. Diagnostic criteria for LGS have recently been defined by the International League Against Epilepsy (ILAE). We aimed to apply these criteria in the real-world setting. We applied ILAE diagnostic criteria to a cohort of patients diagnosed with LGS by epileptologists following inpatient video-EEG monitoring (VEM) at tertiary comprehensive epilepsy centres between 1995 and 2015. We also assessed mortality in this cohort. Sixty patients diagnosed with LGS and had complete records available for review were Identified. Among them, 29 (48%) patients met ILAE diagnostic criteria for LGS (ILAE-DC group). Thirty-one did not meet criteria (non-ILAE-DC) due to absence of documented tonic seizures (n=7), EEG features (n=12), or both tonic seizures and EEG features (n=10), intellectual disability (n=1), or drug resistance (n=1). The ILAE-DC group had a shorter duration of epilepsy at VEM than the non-ILAE-DC group (median = 12.0 years Vs 23.7 years, respectively; p=0.015). The proportions of patients with multiple seizure types (100% vs. 96.7%), ≤2.5Hz slow spike-and-wave EEG activity (100% vs. 90%), seizure-related injuries (27.6% vs 25.8%), and mortality (standardized mortality ratio 4.60 vs. 5.12) were similar between the groups. Up to 52% of patients diagnosed with LGS following VEM may not meet recently accepted ILAE criteria for LGS diagnosis. This may reflect both the limitations of retrospective medical record review and a historical tendency of applying the LGS diagnosis to a broad spectrum of severe, early-onset drug-resistant epilepsies with drop attacks. The ILAE criteria allow delineation of LGS based on distinct electroclinical features, potentiating accurate diagnosis, prognostication, and management formulation. Nonetheless, mortality outcomes between those who did and did not meet ILAE diagnostic criteria for LGS were similarly poor, and both groups suffered high rates of seizure-related injury.