SEEG-guided radiofrequency thermocoagulation of the epileptogenic networks: Its utility for both treatment and validation for localizing epileptogenic networks.

Introduction: Stereoelectroencephalography-guided radio-frequency thermo coagulation (SEEG-RFTC) is a minimally invasive technique whereby radiofrequency-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: 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 over the seizure onset zone(SOZ) was performed at the bedside, electrodes were then explanted. If seizures were still not, this was followed by surgery over SOZ.

Results: 61 patients underwent SEEG-RFTC, 41 males. Mean duration of seizures: 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, and 9-localization on SPECT/PET/MEG but MRI doubtful, 4-eloquent cortex and 5 had bilateral substrates. Seizure onset zone- frontal-18, temporal-35, insula-3, occipital-4, parietal-1. A total of 406 electrodes implanted, a mean 8.2+3.5/ patient. Mean follow up: 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 (Class I & II). 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 I & I outcomes were 37% in MRI -ve and 53.8% in MRI +ve cases (p<0.01). The transient 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% Class I & II, 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.