Biomarkers of Response to SEEG Thermocoagulation

Drug-resistant focal epilepsy is a severe neurological disease that affects one-third of patients with epilepsy. Surgery is the only potentially curative treatment. Intracerebral exploration by stereo electroencephalography (SEEG) is an important step in the surgical pathway. It aims to establish the precise mapping of the epileptogenic network (EZN), including all the brain regions that generate seizures. At the end of SEEG, SEEG-guided radiofrequency thermocoagulation (SEEG RFTC) represents a therapeutic option that may be efficient as a palliative treatment in patients ineligible for resective surgery, or may lead, in some cases, to a definitive effect, avoiding open surgery. The safety and effectiveness of this approach have been established. However, the odds of remaining seizure-free after one year vary greatly between studies, ranging from 4% to 71%. This disparity in therapeutic responses could be linked to the absence of objective criteria for the selection of targets, but also to the existence of mechanisms of action outside of the direct lesional effect. A decrease in SEEG markers of epileptogenicity may predict thermocoagulation efficiency. However, no data are available regarding changes in alteration of the blood-brain barrier (BBB) connectivity, inflammation, or associated molecular changes and their relationship to prognosis. This study aims to elucidate the mechanisms underlying the clinical effect of SEEG RFTC by studying the changes in electrophysiological (SEEG), structural (ultra-high field MRI), and biological (blood biomarkers of neuro-glio-vascular damage and inflammation, molecular adaptations) markers. They will be correlated with clinical outcome in a prospective cohort of patients with drug-resistant focal epilepsy. As advantages for clinical care, this study will allow selection of RFTC targets based on scientifically validated criteria, and elaboration of predictive scores for therapeutic response in each patient. The primary objective is to study the predictive factors of response to SEEG RFTC, by correlating changes in BBB permeability with clinical response 3 months after RFTC, in a prospective cohort of patients with drug-resistant focal epilepsy.