Abstracts

Rationale: Stereoelectroencephalography (SEEG) based presurgical evaluation of epilepsies has two objectives: to define the epileptogenic zone (EZ) and to map cortex functionally in relation with the surgical plan. The aim of this study is to analyze electrical stimulation (ES) findings in our population of patients and to observe if there is a difference of response between the diverse anatomical regions depending of the setting of stimulation. Methods: We analyzed 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 analyzed, we divided 6 anatomical areas (hippocampus, Amygdala, Frontal, Temporal, Insula and Parieto-occipital), and evaluated any evoked clinical response with changes in the electric activity, depending on the charge density.We found that in Amygdala the arithmetic average of charge density that is needed to evoke a clinical and electrical response is 49.35 uC/cm2 (SD: 37.01uC/cm2), in hippocampus is 49 uC/cm2(SD: 24uC/cm2), Frontal areas is 83uC/cm2 (SD: 49uC/cm2), in Temporal areas is 82.23 uC/cm2 (SD: 32.89uC/cm2), in Insula areas is 82.23uC/cm2 (SD: 49,39 uC/cm2) and in Parieto-occipital areas is 65.78uC/cm2 (SD: 32.89uC/cm2). Conclusions: In this analysis we observed that hippocampus and amygdala regions were more susceptible to evoke a clinical response with minimal charge density, while Frontal, lateral Temporal, Insula and  parieto-occipital regions needs more charge density to trigger a clinical response.   Funding: Enys. CONICET