Abstracts

Rationale: Stereoelectroencephalography (SEEG)- based presurgical evaluation of epilepsies has a double objective: to define the epileptogenic zone (EZ) and to map cortex functionally in relation with the surgical plan. The aim of this study is to analize electrical stimulation (ES) findings in our population of patients. Methods: We analized 17 patients from the Video-EEG Unit of the Neuroscience Service from El Cruce Hospital, with drug resistant epilepsy who underwent a SEEG as part of a surgical plan. Electrode size diameter of 1,57 to 1,12 mm, contacts 1.57 to 2.41 mm long, separated by 5 mm from one another.ES is applied between two adjacent leads of one electrode. Stimulation parameters:Bipolar 40Hz - 1mseg , T 2 a 5 seg, Pulse width and train frequency generally are kept constantthroughout the whole stimulation procedure, intensity rangefrom 1 to 10 mA, charge density (uC/cm2) from 12,34 to 123,38, until trigger after-discharges (AD), or clinical response.Cognitive tasks: hand tapping, naming, automatic speech (counting), reading and verbal fluency. Results: From the 17 patients, we trigger theirsusual seizures in 15 (89%). From them,we trigger the seizures in 82 opportunities. 13 (15.85%)were trigger when we stimulated hippocampus, 5 (6.09%) amygdala, 28 (34.15%) other temporal areas, 42 (51.21%) frontal areas, 13 (15.85%)parieto-occipital areas. In 10 (58.82%) patients we map eloquent brain regions, 6 (35,3%) language, 4 (23.53%) patients were evaluated the motor area, 2 (11.76%)sensitive areas, 3 (17.65%) visual and3 (17.65%)auditory sensations. We define EZ in 15 (88.23%) of patients, 3 (17.65%) mesial temporal lobe epilepsy, 7 (41.18%) frontal lobe epilepsy, 4 (23.53%) parieto-occipital epilepsy, 1 (5.88%) insular epilepsy. Conclusions: ES is a procedure that allowed us, along with the electroclinical analysis of the spontaneous seizures and the interictal recording, the accurate location of the EZ, the temporal space dynamics of the epiletogenic network and the functional mapping, to plan cortical resection without overlap and to improve post-surgical prognosis. Funding: Enys. CONICET