A three-dimensional conformal radiofrequency thermocoagulation method for epileptogenic zones in functional cerebral areas: evaluation and prediction of surgical outcomes

Abstract Background Stereo-electroencephalography (SEEG)-guided radiofrequency thermocoagulation (RF-TC) emerges as a feasible alternative for drug-resistant focal epilepsy with epileptogenic zones (EZs) located in functional cerebral areas, which is ineligible for resection surgery. However, the efficacy of RF-TC was considered limited. This study described a three-dimensional conformal SEEG-guided RF-TC method to enhance thermocoagulation efficacy and assessed its surgical outcomes in patients with EZs located in functional cerebral areas. Methods Ten patients were retrospectively reviewed, and the pathogeneses included focal cortical dysplasia (FCD, n = 5) and gray matter heterotopia (GMH, n = 5). Three-dimensionally symmetrical electrode placement was designed based on reconstructed cerebral model integrating the etiology and surrounding cerebral cortices, vessels and fibers. The three-dimensional conformal SEEG-guided RF-TC procedure in the functional area was performed by these electrodes penetrating the etiology conformally. Two electrophysiological indicators extracted from SEEG recordings, specifically line length (LL) and approximate entropy (ApEn), were calculated and a support vector machine (SVM) classifier was used to predict outcomes. Results Eight patients (80%) achieved Engel class I and International League Against Epilepsy class 1–2 (responders), whereas two patients (20%, one with FCD and one with GMH) did not present long-lasting seizure freedom (non-responders). The sole short-term complication observed was decreased limb muscle strength, with no case of short-term deficits developing into long-term complications. LL and ApEn exhibited different postoperative changes in responders and non-responders. The changes were used to predict outcomes, achieving a 98.05% area under the receiver operating characteristic curve based on SVM. Conclusions The three-dimensional conformal SEEG-guided RF-TC method shows a potentially favorable risk–benefit ratio. Postoperative changes of short-term electrophysiological indicators LL and ApEn are promising tools for prognostic prediction.