Propagation of electrical field in the brain using electrical intra-cerebral stimulations

For drug resistant partial epilepsy, intra-cerebral electrical stimulation (Deep Brain Stimulation--DBS) constitutes one of the means to locate epileptic volume. This paper investigates, in the framework of source localization problem, the propagation of the electrical field and current density distribution induced in the brain during in vivo electrical stimulation. There are three objectives in this work: to validate the propagation model for different large frequencies, to highlight the problem of the close field with the DBS source and to show the influence of the proximity to the skull on the results. We compared the Stereo-EEG data, recorded during DBS, with those obtained using: (i) the simplest model, the dipolar model in an infinite homogeneous medium, (ii) a more realistic approach with a numerical method, the Boundary Element Method (BEM). Studies on ten subjects with 234 stimulations showed that the dipole model could be used in the brain far from the skull in direction of dipole moment but that BEM was more appropriate close to the skull.