Improvements on spatial coverage and focality of deep brain stimulation in pre-surgical epilepsy mapping

COLLAVINI, SANTIAGO; FERNÁNDEZ CORAZZA, MARIANO; ODDO, SILVIA; PRINCICH, JUAN PABLO; KOCHEN, SILVIA; MURAVCHIK, CARLOS HORACIO

JOURNAL OF NEURAL ENGINEERING

IOP PUBLISHING LTD

Año: 2021 vol. 18 p. 1 - 19

1741-2560

Objective. Electrical stimulation mapping (ESM) of the brain using stereo-electroencephalography(SEEG) intracranial electrodes, also known as depth-ESM (DESM), is being used as part of thepre-surgical planning for brain surgery in drug-resistant epilepsy patients. Typically, DESMconsists in applying the electrical stimulation using adjacent contacts of the SEEG electrodes and inrecording the EEG responses to those stimuli, giving valuable information of critical brain regionsto better delimit the region to resect. However, the spatial extension or coverage of the stimulatedarea is not well defined even though the precise electrode locations can be determined fromcomputed tomography images. Approach. We first conduct electrical simulations of DESM fordifferent shapes of commercial SEEG electrodes showing the stimulation extensions for differentintensities of injected current. We then evaluate the performance of DESM in terms of spatialcoverage and focality on two realistic head models of real patients undergoing pre-surgicalevaluation. We propose a novel strategy for DESM that consist in applying the current usingcontacts of different SEEG electrodes (x-DESM), increasing the versatility of DESM withoutimplanting more electrodes. We also present a clinical case where x-DESM replicated the fullsemiology of an epilepsy seizure using a very low-intensity current injection, when typical adjacentDESM only reproduced partial symptoms with much larger intensities. Finally, we show oneexample of DESM optimal stimulation to achieve maximum intensity, maximum focality orintermediate solution at a pre-defined target, and one example of temporal interference in DESMcapable of increasing focality in brain regions not immediately touching the electrode contacts.Main results. It is possible to define novel current injection patterns using contacts of differentelectrodes (x-DESM) that might improve coverage and/or focality, depending on thecharacteristics of the candidate brain. If individual simulations are not possible, we provide theestimated radius of stimulation as a function of the injected current and SEEG electrode brand as areference for the community. Significance. Our results show that subject-specific electricalstimulations are a valuable tool to use in the pre-surgical planning to visualize the extension of the stimulated regions. The methods we present here are also applicable to pre-surgical planning of tumor resections and deep brain stimulationtreatments.