Multimodal Imaging in Pre-surgical Evaluation of Epilepsy (EPIMAGE)

Contribution of Multimodal Imaging (MRI, PET, MEG) in Pre-surgical Evaluation of Drug-resistant Focal Epilepsy

Epilepsy is the most common chronic neurological disorder in the world, affecting more than 50 million people worldwide. Approximately 35% of patients with epilepsy are refractory to all available antiepileptic drugs. Drug-resistant epilepsies are often partial or focal. Patients with drug-resistant focal epilepsy suffer from an increased risk of death, primarily due to seizure-related fatalities, in comparison with the general population. The only therapeutic option for this form of epilepsy is the surgical removal of the region of the brain responsible for seizures, called the epileptogenic zone (EZ). This requires the precise localization of the EZ based on a comprehensive pre-surgical evaluation of patients. Today the gold standard for localizing the EZ and validating a non-invasive technique for localization of the EZ remains intracerebral stereo-EEG (stereo-electroencephalography or SEEG) recordings of spontaneous seizures. The implementation strategy of the intracerebral depth electrodes is guided by clinical and neuroimaging data, including anatomical Magnetic Resonance Imaging (MRI), Positron Emission Tomography (PET) with FDG (fluoro-Deoxy-Glucose) and MagnetoEncephaloGraphy (MEG). Although the contribution of each technique in the pre-surgical localization of the EZ has already been shown, no wide-scale study has examined the cumulative contribution of these three techniques.

The purpose of this study is (i) to evaluate rigorously the diagnostic value of multimodal imaging for non-invasive localization of the EZ and (ii) to better target the indications for intracerebral recordings (SEEG).

Localizing value of MEG, FDG-PET and MRI for the determination of the Epileptogenic Zone defined by SEEG recordings

Pathological volumes defined by multimodal imaging (MEG, FDG-PET and MRI) will be compared to the topography of the EZ defined by SEEG recordings. For each patient, we will sum the total number of intracerebral depth electrodes included in the EZ. Then, for each functional volume obtained from multimodal data fusion, we will count the total number of electrodes in the latter (Vol elec_tot) and the number of electrodes included in the EZ (Vol elec_ze).

For each functional volume, two parameters will be defined: sensitivity and specificity. These parameters will be calculated as follows: sensitivity = (Vol elec_ze) / (Pat elec_ze) and specificity = (Vol elec_ze) / (Vol elec_tot).

Inclusion Criteria: Patient with drug-resistant focal epilepsy Candidates for pre-surgical evaluation including FDG PET, MRI, MEG and SEEG recordings. Age 18-65 years EEG-confirmed focal epilepsy for >2 years Signed informed consent form. Exclusion Criteria: Age <18 years and >65 years Contraindication to the MRI Pregnant woman Head size incompatible with MEG recordings Adult subject to legal protection measure.

100 patients with drug-resistant focal epilepsy and candidates for epilepsy surgery will be recruited.