S56 Added value of EEG signal analysis in presurgical evaluation for drug-resistant epilepsy

Objectives To assess the role of signal analysis methods for accurate delineation of the epileptogenic zone during surgery for drug resistant epilepsy. Methods We used surface video EEG as well as invasive studies by means of the stereo-EEG method to identify the epileptogenic networks. Signal analysis tools have been applied systematically during pre surgical evaluation to study ictal as well as interictal activity and responses to different stimulation protocols. Connectivity charts were computed based on analysis of cortico-cortical evoked potentials on single pulse electrical stimulation (SPES). The results were interpreted according with an individual patient hypothesis and integrated with clinical and anatomic data. Results We explored 63 patients at the University Hospital of Bucharest in the National Program for Epilepsy Surgery between 2012 and 2016 of which 57 received either open surgeries or undergone a procedure of radio frequency thermocoagulation (RFTC) applied on intracranial electrodes. In the group of patients ( n = 34) with more than 2 years follow up after surgery, 25 (74%) are seizure free. Signal post processing analysis was critical for surgical planning in 12 cases (48%). Discussion Systematic use of signal analysis approach improved the definition of surgical resection limits, made the recording sessions shorter without sacrificing information, and allowed a better definition of targets for RFTC protocols during SEEG recordings. Conclusion Signal analysis tools added complementary information where the traditional visual analysis was not helpful for surgical planning. Significance Post processing methods of the EEG signal integrated with the anatomo-clinical hypothesis offer unbiased valuable data to improve surgical outcome.