Diagnosing Lennox–Gastaut syndrome in adulthood: A scoping review of diagnostic challenges and age‐related electroclinical evolution

OBJECTIVE: Lennox-Gastaut syndrome (LGS) is a developmental and epileptic encephalopathy typically diagnosed in childhood. The 2022 International League Against Epilepsy (ILAE) criteria provide a diagnostic framework built on pediatric data, but their applicability in adulthood is challenged by disease evolution, treatment effects, and missing pediatric records. This scoping review aimed to identify adult LGS features and to evaluate the adaptability of current criteria in adults. METHODS: We conducted a systematic search on MEDLINE (PubMed) following the Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) guidelines. Studies involving individuals 16 years of age and older with LGS or suspected LGS were included. Data were extracted on seizure semiology, electroencephalography (EEG) patterns, comorbidities, and etiological factors across the lifespan. RESULTS: Forty-five sources (78% case reports/series) encompassing 421 patients were included, with substantial heterogeneity in reporting. The analysis suggests a longitudinal attenuation or under-documentation of several classical LGS features: studies with fulfillment of the ILAE seizure-type criteria decreased from 73% in childhood to 41% in adulthood; tonic seizures often persisted (frequently during sleep), whereas atonic and atypical absence seizures significantly declined. The mandatory EEG hallmarks (generalized paroxysmal fast activity and slow spike-and-wave complexes) were documented in less than half of adult patients, possibly due to the reduced frequency of sleep EEG monitoring. Comorbidities were reported inconsistently, representing a major knowledge gap, as sleep and behavioral disorders may further mask diagnostic markers. SIGNIFICANCE: Given the heterogeneity and predominantly low-level evidence of the included literature, these findings warrant cautious interpretation; nonetheless, strict adherence to pediatric-centric criteria in adults may plausibly contribute to underdiagnosis or false negatives. Transitioning from a "snapshot" to a "longitudinal" diagnostic mindset is essential. Clinicians should prioritize life-spanning anamnesis and recognize that the clinical and EEG core criteria of LGS may evolve or diminish over time. Age-adapted diagnostic frameworks are needed to ensure that adult patients receive appropriate diagnosis and therapeutic pathways.