[Stereo-EEG-guided radiofrequency thermocoagulations in drug-resistant focal epilepsy].

Background: Preoperative examination of patients with focal drug-resistant epilepsy requires invasive diagnostic methods in 30-40% of cases. Stereo-EEG is one of them and often the most significant for verification of epileptogenic zone and its subsequent resection. The desire to minimize surgical trauma led to idea of local radiofrequency thermocoagulation through SEEG electrodes [1]. This allows destruction of epileptogenic zones during examination. Despite the safety of this method, appropriate studies are contradictory and require further analysis [2].

Objective: To clarify the role of radiofrequency thermocoagulation in diagnosis and treatment of patients with focal drug-resistant epilepsy.

Material and methods: A single-center retrospective study included 75 patients with focal drug-resistant epilepsy who underwent radiofrequency thermocoagulation between 2020 and 2023. The results were assessed 6 and 12 months after thermocoagulation.

Results: Six-month freedom from seizures was 35% (26 patients). Seizure rate decreased by more than 50% (McHugh I-II) in 39 (52%) patients. Most patients with the McHugh II outcome (10 out of 12) experienced less incidence and intensity of seizures. This made unnecessary subsequent surgery. MR-negative nature of epilepsy (p=0.015), right-sided localization of epileptogenic substrate (p=0.032) and bihemispheric distribution (p=0.05) were negative predictors of treatment outcomes. A relationship was found between localization of radiofrequency thermocoagulation in the frontal lobe and freedom from seizures. Mean volume of one thermocoagulation point was 0.98±0.3 cm³. The number of points did not significantly influence the outcomes either for the McHugh scale (p=0.654) or for the Engel scale (p=0.288). Total volume of thermocoagulation foci ranged from 0.52 to 13.5 cm³ (mean 3.85±2.9). Twenty-six (35%) patients underwent surgery for persistent and/or recurrent seizures after radiofrequency thermocoagulation (SEEG-guided resection of epileptogenic zones). After 12 months, freedom from seizures was 28% (21 patients), seizure rate decrease by more than 50% (McHugh I-II) was observed in 33 (44%) patients. McHugh class III outcome was observed in 12 patients (16%). MR-negative nature of epilepsy (p=0.009) and right-sided localization of epileptogenic substrate (p<0.001) were negative predictors regarding Engel I outcomes.

Conclusion: Stereo-EEG-guided radiofrequency thermocoagulation is a unique and safe technique significantly reducing the incidence and intensity of epileptic seizures in patients with focal drug-resistant epilepsy with minimal iatrogenic risk.