Stereoelectroencephalography in the Presurgical Evaluation of Drug–Resistant Epilepsy: Retrospective Analysis of Clinical Efficacy and Safety in 71 Procedures

Background Stereoelectroencephalography (SEEG) is a pivotal diagnostic and therapeutic tool in the presurgical evaluation of patients with drug-resistant epilepsy, particularly when noninvasive investigations are inconclusive. Objective To evaluate the indications, technical aspects, safety profile, and clinical outcomes of SEEG, including the adjunctive role of SEEG-guided radiofrequency thermocoagulation (RF-TC). Methods We conducted a retrospective review of 71 consecutive patients with drug-resistant epilepsy who underwent SEEG monitoring at our institution between 2016 and 2025. Demographic, neuroimaging, and electrophysiological data were analyzed, along with surgical variables, perioperative complications, and outcomes following SEEG-guided RF-TC and subsequent resective surgery. Results A total of 958 electrodes were implanted (mean 14 ± 4.5 per patient). SEEG confirmed the preimplantation hypothesis in 85% of cases. RF-TC was performed in 37 patients (52%); among them, 27 patients (73%) showed seizure improvement at 12 months. According to the Engel classification, 14% achieved class I, 27% class II, 19% class III, and 41% class IV outcomes. Complications occurred in 14 patients (20%), predominantly minor radiological findings; only one patient (1%) developed a permanent neurological deficit. Among the 37 patients who underwent resective surgery, favorable seizure outcomes (Engel classes I–II) were achieved in 76%, 70%, and 71% at 3, 6, and 12 months, respectively. Conclusions SEEG is a safe and effective modality for presurgical evaluation in drug-resistant epilepsy. It improves localization of the epileptogenic zone (EZ), guides individualized surgical decision-making and provides therapeutic benefit through RF-TC in carefully selected patients.