O-48 Interictal discharges neuromodulation using transcranial electrical stimulation : a simultaneous tDCS-SEEG study in human in vivo

Abstract

Transcranial direct current stimulation (tDCS) has demonstrated its ability to shift the balance of cortical inhibition and excitation (Reato D et al., 2013). In this preliminary in vivo study, we investigated the effect of tDCS in drug-resistant epileptic patients using simultaneous stereoelectroencephalography (SEEG) recordings. Our objective was to determine if cathodal stimulation can inhibit the epileptic discharges using SEEG analysis as ground truth. Two drug-resistant patients were included. The anatomical target (i.e. the irritative zone) was defined by epileptologists according the first days of SEEG recordings. A 20-min resting state session (sham condition) was acquired before the tDCS. Then, a single 20-min session of cathodal tDCS (intensity: −1 mA) was applied over the irritative zone. tDCS montages (anode and cathode) were obtained using individual MRI and numerical simulations (ROAST algorithm). Automatic epileptic discharges detection was performed and then validated by visual inspection. For the medial temporal lobe study, we detected respectively 64 and 33 discharges before and during tDCS. The averaged amplitudes in the hippocampus were respectively 742 ± 422 mV and 152 ± 43 mV (decrease of 20%). For the lateral temporal lobe study, we detected respectively 192 and 165 discharges. The averaged amplitudes were respectively 136 ± 55 μV and 117 ± 36 μV (decrease of 14%). These absolute amplitude decreases were statistically significant (p < 0.001). Here, we demonstrated that the tDCS can reduce the number and the amplitude of epileptic discharges both in deep and lateral brain structures. This result also indicates that tDCS can pass through the skull and propagate in the brain tissues.