Authors :
Presenting Author: Christopher Hagen, PhD – Cook Children's
Eryn Armstrong, MS – Cook Children's
Amy Davis, RN – Cook Children's
Cynthia Keator, MD – Cook Children's
Rationale:
Lennox-Gastaut Syndrome (LGS) is a developmental and epileptic encephalopathy (DEE) characterized by multiple drug-resistant seizure types, distinct EEG patterns, and cognitive and behavioral deficits. In 2022, the International League Against Epilepsy (ILAE) updated the required EEG features for diagnosis to include both slow spike-and-wave (SSW) and generalized paroxysmal fast activity (GPFA), whereas previously only SSWs were mandatory for diagnosis. Other requirements include clinical onset prior to 18 years and multiple drug-resistant seizure types, one of which must include tonic. In 2023, ICD10 code G40.81x was approved for LGS. Given the importance of ICD10 accuracy in conducting research using electronic health records, this single center review aimed to investigate the proportion of patients at Cook Children’s Medical Center (CCMC) identified as LGS by ICD10 code who met the updated ILAE diagnostic criteria as well as how these criteria emerge across age.
Methods:
Patients diagnosed with LGS using ICD10 code G40.811-814 and seen in the pediatric neurology clinic between January 2024 and July 2025 were retrospectively reviewed for the presence of LGS symptoms including developmental delay, tonic seizures, and SSWs and GPFA on EEG, including the first dated appearance of these features. Final LGS diagnosis dates were also captured. In cases where the EEG reports did not explicitly report SSW or GPFA, raw EEG recordings were pulled and reviewed by an epileptologist to confirm findings.Results:
Of the 294 patients with LGS diagnoses, chart review revealed 263 (89.5%) had histories of tonic seizures, 202 (68.7%) had EEG evidence of SSWs, and 89 (30.3%) had EEG evidence of GPFA. 125 patients (42.5%) had tonic seizures with only SSWs and 73 (24.8%) exhibited all three features. Of patients who exhibited all diagnostic criteria, it was found that on average symptoms appeared in order of developmental delay (M = 4.4 years, SD = 3.97), tonic seizures (M = 5.06, SD = 3.87), SSWs (M = 5.39, SD = 4.00), GPFA (M = 7.72, SD = 4.49), followed by final diagnosis (M = 8.31, SD = 4.49). A significant age difference also emerged between the first appearance of SSWs and GPFA (p < .01). Conclusions:
These results reveal that the majority of patients at this institution fail to meet the current ILAE electroclinical diagnostic criteria. As the implication for misdiagnosis can have profound impact, this data supports verification of diagnosis using health record review in addition to ICD10 coding. Moreover, it highlights the need for a standardized system for capturing relevant diagnostic data for research and epidemiological purposes, especially considering the diversity of clinical practices for EEG reporting and evaluation. Further, these data give insight into the progression of LGS symptomology and how the dynamic clinical presentation of LGS can make an accurate diagnosis difficult. Ultimately, ensuring accurate diagnosis and data capture would lead to more targeted LGS research for natural history studies, clinical trial recruitment, and prognostic evaluation.Funding: n/a