Ictal phase–amplitude coupling supports surgical decision-making in MRI-negative epilepsy with non-localizing SEEG: an illustrative case

We report a 14-year-old boy with MRI-negative drug-resistant frontal lobe epilepsy presenting with the chapeau de gendarme sign. SEEG showed diffuse low-voltage fast activity with rapid bilateral propagation, precluding reliable visual localization. Ictal phase-amplitude coupling (PAC) analysis revealed a right-dominant increase in modulation index at seizure onset, localizing to the anterior insula and adjacent prefrontal cortex. Informed by these findings, right frontal disconnection with operculo-insular resection was performed, resulting in seizure freedom at 1 year. This case highlights the utility of ictal PAC analysis in guiding surgical decision-making when SEEG findings are non-localizing.