SEEG-Guided Radio-Frequency Thermocoagulation of the Epileptogenic Networks: Its Utility for Both Treatment and Validation for Localizing Epileptogenic Networks.

INTRODUCTION: Stereoelectroencephalography-guided radio-frequency thermocoagulation (SEEG-RFTC) is a minimally invasive technique whereby radio-frequency thermocoagulation is performed using SEEG electrodes, following recording and stimulation. It helps to disconnect/disrupt or ablate the epileptogenic networks and provides both therapeutic and diagnostic abilities.

METHODS: This study is a retrospective study (2016-2024). All underwent comprehensive epilepsy surgery workup (video EEG, MRI, ictal-SPECT, PET, and magnetoencephalography). SEEG was placed using robotic guidance. Recording of habitual seizure following stimulation (to produce seizures) was performed followed by SEEG-RFTC in the seizure onset zone (SOZ) at the bedside; electrodes were then explanted. If seizures recurred or were not controlled, this was followed by surgery over SOZ as guided by SEEG stimulation-induced functional mapping of eloquent cortices.

RESULTS: Sixty-one patients underwent SEEG-RFTC, 41 males. Mean duration of seizures was as follows: 11 years; seizure frequency range 1-100/day. As per imaging, 5 had definite lesions, 12 dual substrates (either adjacent or distant), 5 doubtful lesions, 21 non-lesional on MRI, 9 localization on SPECT/PET/MEG but MRI doubtful, 4 eloquent cortex involvement, and 5 had bilateral substrates. SOZ was frontal in 18, temporal 35, insula 3, occipital 4, parietal 1. A total of 406 electrodes were implanted, a mean of 8.2 ± 3.5/patient. Mean follow-up was 42 ± 17.4 months. About 72% (44/61) responded transiently (mean transient seizure-free time 95 ± 19 days). Of these, 29 underwent surgery; 48% had good outcomes (classes 1 and 2). Overall, 22% (14/61) had good outcomes with SEEG-RFTC as stand-alone procedure (follow-up 28 + 6.2 months, range 6-32 months). The class 1 and 2 outcomes were 37% in MRI-negative and 53.8% in MRI-positive cases (p < 0.01). The transient seizure-free time in our study did not correlate with good outcomes, but presence or absence of a substrate did. Temporal substrates had better outcomes than extra-temporal (57% vs. 47%, classes 1 and 2, p < 0.01).

CONCLUSION: SEEG-RFTC is a minimally invasive and effective adjuvant to SEEG recording and stimulation, may be done bedside under awake conditions, and helps to disrupt/disconnect/ablate the abnormal networks. It may be therapeutic or can strengthen the hypothesis for a later surgical resection.