Abstract:Objective To investigate the electroencephalogram (EEG) characteristics and progression of febrile infection-related epilepsy syndrome (FIRES) in children, aiming to enhance diagnosis and treatment approaches.Methods A retrospective analysis was conducted on 26 children with FIRES between May 2017 and December 2021.Results All 26 children (100%) presented with fever at the onset, followed by frequent convulsions that rapidly progressed into convulsive status. Ventilator support was required for 22 cases (85%). During the acute phase, EEG features demonstrated the disappearance of background activity and physiological sleep cycles in all children. Diffuse slow waves and multifocal slow spike slow waves were observed as abnormal waves during the interictal period. A characteristic pattern of focal low amplitude fast wave initiation was detected in all children during seizure episodes. In the chronic phase, the background EEG activity gradually recovered, and the presence of abnormal waves was relatively limited. The characteristic pattern of focal slow wave rhythm initiation was evident during seizure episodes. Additionally, extreme δ brushes were observed in four cases (15%).Conclusions These findings suggest that EEG manifestations in children with FIRES exhibit distinctive patterns during the acute and chronic stages, providing significant value for early diagnosis and clinical staging. Extreme δ brushes may be one of the distinctive markers of children with FIRES.