Authors :
Presenting Author: Maëva Daoud, MSc – Aix-Marseille University
Samuel Medina Villalon, ENG – Timone Hospital APHM; Ricardo Salvador, ENG – Neuroelectrics Barcelona (Spain); Maria Fratello, ENG – Aix-Marseille University (France); Khoubeib Kanzari, ENG – Aix-Marseille University (France); Giada Damiani, ENG – Neuroelectrics Barcelona (Spain); Elodie Garnier, ENG – Aix-Marseille University (France); Giulio Ruffini, PhD – Neuroelectrics Barcelona (Spain); Christian Benar, PhD – Aix-Marseille University (France); Fabrice Bartolomei, MD, PhD – Timone Hospital APHM
Rationale:
Transcranial direct current stimulation (tDCS) is a non-invasive neuromodulatory technique that has been investigated as a potential alternative treatment for patients suffering from drug-resistant epilepsy (DRE). tDCS aims at modulating the exacerbated excitability of the epileptogenic zone (EZ) thanks to a constant weak electrical current across the cortex, tDCS may use two scalp electrodes (conventional tDCS), or a set of several electrodes (multichannel tDCS), in order to optimize stimulation focality [1,2]. Previous studies have explored the potential of tDCS to reduce seizure frequency (SF) [Literature review 3]. In a preliminary study, we highlighted induced-changes in global functional connectivity after multichannel tDCS in patients presenting a good response to tDCS [4]. Our goal here was to identify the brain regions involved in these functional changes thanks to magnetoencephalography (MEG) data acquired during a tDCS long-term protocol in patients suffering from DRE (GALVANI PS1 NCT04782869).
Methods:
Ten patients suffering from DRE received a six months therapy of tDCS with three cycles of stimulation repeated every two months. Each cycle consisted in five consecutive days of 40 minutes with cathodal multichannel tDCS, personalized according to the epileptogenic zone of each patient. MEG recordings were performed before and after each stimulation cycle in order to estimate the source signals based on spatial filtering (beamforming). Functional connectivity (FC) changes were analyzed at source level in order to identify the induced changes in brain networks and to correlate these modifications with clinical response (seizure frequency (SF) changes).
Results:
In the ten first recruited patients that achieved the study, 6/10 patients were clinically improved because as they presented a decrease in their SF after three cycles of tDCS. Furthermore, we obtained a significant (p=0.0075) positive correlation between SF and FC changes within the inhibited targeted brain regions (surrounding the cathodal electrodes). Finally, we observed a greater decrease of FC specifically on the targeted inhibited brain regions in the clinically improved patients than in the non-improved patients (p< 0.05).