Retrospective identification of LGS using EHR data is challenging due to nonspecific terminology, incomplete medical records, and inconsistent documentation. A clear, complete textual description of EEG waveform details in medical records is a crucial element in assigning a diagnosis of LGS in retrospective studies. In a multicenter review of 935 patients across seven pediatric epilepsy centers, epileptologist reviewers disagreed on the diagnosis of LGS in 11% of cases.