Transcranial direct current stimulation (tDCS) modify the interictal epileptiform activity in deep cerebral structures observed on SEEG (stereoelectroencephalographie)

tDCS is a widely investigated noninvasive neuromodulation technic in neurological and psychiatric disorders. Some studies demonstrate the effect of tDCS on interictal epileptiform discharges (IED) (Fregni et al., 2006). The objective of our study was to investigate the tDCS effect on IED (frequency of occurrence and amplitudes) in intracerebral structures thanks to SEEG investigation. Two patients with focal drug-resistant epilepsy were included: one medial and one lateral temporal lobe epilepsy. In average, they were implanted with 15 SEEG electrodes. Thanks to the SEEG recordings (5 days), epileptologists localized the irritative zone. The experiment was divided in 3 sessions: 20min sham, then 20min tDCS (−1mA) and finaly 20min sham. The amplitudes and the number of occurrences were analyzed. The results were compared between the sessions. For the medial temporal lobe study, 64 and 33 IED were detected respectively before and after tDCS. The averaged amplitudes in the hippocampus were respectively 742±422μV and 152±43μV correspond to a 20% decrease (P