Abstracts

Rationale: Invasive monitoring using depth electrodes is relatively under-utilized in North America, where subdural grid/strip mapping is considered the method of choice in many centers. We report our experience at Cleveland Clinic with stereo-electroencephalography (SEEG) regarding its feasibility and safety in the diagnosis and treatment of intractable epilepsy. Methods: We prospectively analyzed 55 patients who underwent SEEG implantation during the period of March 2009 to May 2010. The main goals for SEEG electrode implantation included (1) mapping of the epileptogenic zone and/or (2) definition of cortical function. Indications for SEEG included discordant pre-operative data, presumed proximity of the epileptogenic zone to eloquent areas in the brain, possibility of multifocal or bi-hemispheric epilepsy and failed previous subdural invasive mapping. Information regarding patient s demographics, success in the definition of the epileptogenic zone and surgical complications were prospectively analyzed. Results: The mean age of the studied population was 30 years. The mean follow-up was 7 months after the invasive monitoring procedure. Mean duration of the epilepsy was 19 years. Twenty two patients had their epileptogenic zone located in the temporal lobes and 33 patients were considered extra-temporal. Twenty patients (36%) had normal MRIs. The total number of implanted electrodes was 703 with an average of 13 electrodes per patient. The SEEG method led to the localization of the epileptogenic zone in 51 patients (94%). From this group, 46 patients underwent resective surgery guided by SEEG (83.5%). Seven patients failed previous subdural grid implantation. SEEG localized the epileptogenic zone in all patients from this subgroup. In this highly complex group of patients, SEEG failed to localize the epileptogenic zone in 4 patients (diffuse seizure onset in most contacts and/or ictal semiology preceding SEEG ictal onset). Complication rate was 3%, corresponding to 2 patients with asymptomatic intracerebral hemorrhages. No permanent complications or mortality occurred. Conclusions: The SEEG methodology demonstrated to be safe and efficient in mapping the epileptogenic zone. Long term seizure outcome is necessary to validate this method. Specific indications for SEEG as compared to subdural grid mapping will need further definition