The main objective of this study is to evaluate the feasibility of recording fast-ripples, a potential new biomarker of epilepsy, using the new micro-macroelectrodes developed by Dixi-Medical.

Partial epilepsies are refractory to medical treatment in 30% of the cases (Refractory Partial Epilepsy or RPE). Patients with RPE suffer from social and occupational disability, an increased risk associated with seizures (traumatic brain injury, accidents), but also a higher risk of sudden unexplained death (2 to 3 times higher) than the general population. Moreover, the medical and social burden of these patients is heavy, representing a significant cost to society.

In some cases, surgical treatment with resection of the epileptogenic zone (EZ) can be proposed. The presurgical evaluation includes various investigations seeking to clarify the location of the EZ; but this approach is sometimes insufficient and the definition of the EZ then requires invasive exploration through intracerebral EEG recording (stereo-EEG, SEEG). This latter technique is currently the preferred standard to define the EZ. It involves implanting electrodes in the brain areas suspected to belong to the seizure network. 50 to 70% of patients investigated with this technique will have epilepsy surgery.

In recent years, a series of studies in animals and humans have suggested that some oscillations, very short and at very high frequency (> 250 Hz), called "fast ripples" (FRs) could be a good biomarker of the EZ (for a review see Zijlmans et al, 2012). The FRs are more easily recorded from microelectrode (diameter: 20-40 microns).

The purpose of this study is to evaluate a new medical device designed by DixiMedical to record FRs, combining micro and regular clinical electrodes.

Inclusion Criteria:

• Patient with RPE in whom SEEG is required to precisely localize the seizure focus

Exclusion Criteria:

Patients with SEEG contra-indication:

• severe psychiatric disorders,
• severe agitation during their crisis
• contraindication for performing an MRI: claustrophobia, a cardiac or neural stimulator, ferromagnetic surgical clips, cochlear implants, intraocular metallic foreign body or in the nervous system,
• contraindication to intracerebral investigation (macro-electrodes): ongoing infection, severe associated pathology (cardiac, pulmonary, renal, hepatic), pregnant or nursing women,
• anti thrombotic ongoing treatment.