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<0.001; Mann–Whitney U test). For the lateral temporal lobe study, we detected respectively 192 and 165 discharges. The averaged amplitudes in the superior temporal gyrus were respectively 136±55μV and 117±36μV correspond to a 14% decrease (P<0.001; Mann–Whitney U test).

In this study, we demonstrated that the cathodal tDCS can reduce the number and the amplitude of epileptic discharges in intracerebral structures. The strength of this study is related to the simultaneous SEEG recordings with non-invasive tDCS and the in-vivo human brain investigation (deep and superficial).