Sustained Seizure Freedom After Stereo-Electroencephalography Without Definitive Intervention: Evidence for Network Modulation by Invasive EEG.

Stereo-electroencephalography (sEEG) is a diagnostic technique used to localize seizure-onset networks in drug-resistant epilepsy, typically guiding resection, ablation, or neuromodulation. Sustained seizure freedom after diagnostic implantation alone is rarely described. We describe two patients who achieved long-term remission after sEEG monitoring without definitive surgical intervention. A 39-year-old man with posttraumatic right hemispheric epilepsy underwent implantation of 11 depth electrodes, during which no habitual seizures were captured despite medication withdrawal and provocation. After electrode explantation, he discontinued all antiseizure medications and has remained seizure-free for 71 months. A 63-year-old woman with left temporal epilepsy underwent implantation of 12 depth electrodes; monitoring again failed to capture habitual seizures, although abundant mesial temporal interictal discharges were recorded. After explantation, which was complicated by a small tract hemorrhage, she has remained seizure-free for 20 months on stable cenobamate therapy. These cases add to a limited body of evidence suggesting that sEEG implantation may induce microlesional or network-modulatory effects capable of interrupting seizure propagation, analogous to remission reported after intracranial electrode placement in prior series. Recognition of this phenomenon is clinically important. When no habitual seizures are recorded and early postoperative improvement is observed, a period of extended follow-up may be warranted before pursuing resection, ablation, or neuromodulation. Further study is needed to define predictors of remission, clarify underlying mechanisms, and guide patient counseling regarding this uncommon but meaningful effect of invasive EEG.