Insights from multimodal simultaneous SEEG‐EEG and SEEG‐MEG recordings: A case of combined generalized and focal epilepsy

Despite formal recognition of "combined generalized and focal epilepsy" in the 2017 International League Against Epilepsy classification, its implications for therapeutic decision-making remain ambiguous. We report a case demonstrating how focal cortical pathology can interact with distributed epileptic networks using multimodal electrophysiology. A patient with long-standing presumed generalized epilepsy and a left frontal malformation of cortical development (MCD) underwent multimodal evaluation with simultaneous scalp electroencephalography-stereoelectroencephalography (SEEG; left frontal lesion-targeted implantation with a right frontal sentinel electrode) and simultaneous SEEG-magnetoencephalography (MEG). Simultaneous scalp EEG and SEEG demonstrated generalized spike-wave (GSW) discharges with bilateral frontal and thalamic involvement, without focal interictal epileptiform activity at the lesion site. Direct cortical stimulation of SEEG contacts adjacent to the MCD reproduced habitual seizures, producing localized afterdischarges followed by widespread thalamocortical engagement and delayed focal cortical evolution. Simultaneous SEEG-MEG recordings of GSWs revealed early posterior hemispheric involvement with subsequent frontal recruitment, supporting a distributed network mechanism. Left frontal MCD resection was associated with elimination of convulsive seizures, with persistent thalamic spike-wave activity recorded by a responsive neurostimulator that remained inactive for stimulation. Together, these findings demonstrate the limitations of fixed dichotomous focal-generalized distinctions and highlight the value of network-based approaches to epilepsy classification and surgical treatment.