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.

Inclusion Criteria:

• Patient, parents or legal representative who have given their written informed consent,
• Adult or pediatric patient ≥ 12 years old suffering from drug-resistant focal epilepsy,
• Standardized pre-surgical assessment including medical history, scalp video-EEG and 3T MRI,
• Patients in whom a SEEG exploration for pre-surgical evaluation has been indicated,
• Patient able to understand, speak and write in French,
• Patient able to follow study's procedure,
• Patient beneficiary or affiliated to a health insurance plan.

Exclusion Criteria:

• Epilepsy surgery performed without the requirement of SEEG,
• Contraindication to 3T or 7T brain MRI (patient with a cardiac pacemaker, metallic foreign bodies, non-removable implanted electronic medical devices, claustrophobia, inability to remain in supine position, patient havingwith Vagus Nerve Stimulation (VNS) or Deep Brain Sstimulation (DBS), intrauterine devices or tattoos in the imaging area less than 6 weeks old at the time of the 3T/7T brain MRI),
• Contraindication to gadolinium-based MRI contrast agent (history of allergic or anaphylactic reaction to gadolinium, hypersensitivity to gadoteric acid, meglumine, or any drug containing gadolinium, severe renal failure (glomerular filtration rate, GFR, below 30 ml/min/1.73 m2), patients on dialysis or with a history of kidney disease, such as renal transplantation, a single kidney, or renal malignancy),
• Person protected by articles L1121-5, L1121-6 and L1121-8 of the Public Health Code (pregnant or breastfeeding woman, deprived of liberty by judicial decision, situations of social fragility, adults unable or unable to express their consent),
• Patient in exclusion period of another study.