Model-based design and placement analysis for epidural cortical stimulation

Background.Epidural cortical stimulation (ECS) offers a promising approach for chronic neuromodulation to treat depression. Effective stimulation requires the generation of focal electric fields within targeted cortical regions while minimizing current spread to the scalp, but the influence of device design and implantation strategies remain unclear.Methods. We used computational modeling to evaluate feasibility of ECS in generating fields sufficient for neural activation. We systematically examined how variations in electrode position and orientation, device design, anatomical, and implantation parameters influence E-field distributions in the cortex and scalp.Results.ECS generated E-fields sufficient for neural activation (⩾75 V m^-1) and electrodes over the gyral crown oriented perpendicular to the gyrus maximized the volume of E-fields ⩾75 V m^-1in the left dlPFC. Increasing electrode surface area broadened field spread but reduced penetration depth and required higher current and energy to achieve equivalent E-fields. Incorporating an insulating burr hole cap or insulating sheet substantially reduced scalp currents with modest increases in energy. Cortical E-fields remained consistent across anatomical and implantation variations, supporting robustness. However, these variations required different current amplitudes, energy demands, and scalp currents, highlighting the need for patient-specific programming. Chronic implantation factors, such as tissue encapsulation increased the power required to maintain equivalent stimulation by up to fourfold.Conclusions. Trade-offs between cortical electric field, scalp currents, and energy efficiency highlight the need for informed design, intentional placement, and patient-specific programming for effective ECS. These findings provide a principled framework for ECS optimization and clinical standardization, enabling more consistent and effective therapeutic targeting.