Modelling of the Current Density Distributions during Cortical Electric Stimulation for Neuropathic Pain Treatment

In the last two decades, motor cortex stimulation has been recognized as a valuable alternative to pharmacological therapy for the treatment of neuropathic pain. Although this technique started to be used in clinical studies, the debate about the optimal settings that enhance its efectiveness without inducing tissue damage is still open. To this purpose, computational approaches applied to realistic human models aimed to assess the current density distribution within the cortex can be a powerful tool to provide a basic understanding of that technique and could help the design of clinical experimental protocols. Tis study aims to evaluate, by computational techniques, the current density distributions induced in the brain by a realistic electrode array for cortical stimulation. Te simulation outcomes, summarized by specifc metrics quantifying the efcacy of the stimulation (i.e., the efective volume and the efective depth of penetration) over two cortical targets, were evaluated by varying the interelectrode distance, the stimulus characteristics (amplitude and frequency), and the anatomical human model. Te results suggest that all these parameters somehow afect the current density distributions and have to be therefore taken into account during the planning of efective electrical cortical stimulation strategies. In particular, our calculations show that (1) the most efective interelectrode distance equals 2 cm; (2) increasing voltage amplitudes increases the efective volume; (3) increasing frequencies allow enlarging the efective volume; and (4) the efective depth of penetration is strictly linked to both the anatomy of the subject and the electrode placement.