International Federation of Clinical Neurophysiology standardized stereo-electroencephalography terminology.

OBJECTIVE: Stereo-electroencephalography (SEEG) is an intracranial EEG methodology used in presurgical epilepsy evaluation to precisely delineate the epileptogenic zone and associated networks. Although established for decades, its global adoption has accelerated due to a favorable safety profile and clinical effectiveness. However, inconsistent terminology limits comparability of findings and multicenter collaboration. This guideline addresses this gap by providing standardized SEEG terminology based on international consensus. METHODS: A working group of 41 experts appointed by the International Federation of Clinical Neurophysiology (IFCN) Executive Committee used a modified Delphi process to develop standardized terminology. The process included two meetings and four Delphi rounds, facilitated by two members. Proposals required at least a two-thirds majority for approval. Meetings were video-recorded and the consensus process fully documented. RESULTS: The SEEG glossary defines key background activities, interictal and ictal patterns (including onset, termination, and postictal features), electrical stimulation responses, and common artifacts. Each definition is illustrated with representative examples in both time-domain and time-frequency representations. CONCLUSION: This IFCN guideline establishes standardized SEEG terminology to promote consistent interpretation and multicenter collaboration. SIGNIFICANCE: The glossary provides a framework for future studies assessing the clinical relevance of SEEG patterns.