The comparative study of invasive electroencephalography modalities in temporal lobe epilepsy

Introduction . Invasive video-EEG monitoring (invasive EEG) is indicated in patients with refractory focal epilepsy while localization of the epileptogenic zone is unclear. Methods of invasive EEG in different groups of patients demonstrate variable results. Objective : to analyse the results of invasive EEG via subdural and depth electrodes in patients with refractory temporal lobe epilepsy with mesial temporal lobe seizures. Materials and methods. The series of 37 patients who underwent invasive EEG from 2013 to 2020 was retrospectively analysed. The study includes primary adult patients with structural refractory focal epilepsy with mesial temporal lobe seizures without tumor and vascular pathology. Patients were divided onto 3 groups: 1) with foramen ovale electrodes 2) subdural strip electrodes and 3) combination of subdural strips and depths electrodes. The results of anteromedial temporal lobectomy after 6 months were classified according to Engel scale. Results . A group with foramen ovale electrodes included 7 patients, subdural strips – 23, combination – 7. The seizure onset zone was detected in 36 (97 %) cases. Serious complications were observed in 2 (29 %) cases in the group with foramen ovale electrodes. The mean follow-up in 23 (76 %) patients after resective surgery was 28.3 months. Favourable results (Engel I, II) were observed in 4 (80 %) patients with foramen ovale electrodes, in 8 (67 %) patients with subdural electrodes, in 6 (100 %) with combination. Unfavourable results (Engel III, IV) were noted in 1 (20 %) patient with foramen ovale electrode, in 4 (33 %) patients with subdural strips. Conclusion . All the presented modalities of invasive EEG are effective for localizing of seizure onset zone in this category of patients. Foramen ovale electrode using may be limited due to increased risk of complications.