Modelling of the Temperature Changes Induced by Transcutaneous Spinal Direct Current Stimulation (tsDCS)

Transcutaneous spinal direct current stimulation is a neuromodulation technique recently exploited to regulate the activity and enhance plasticity of spinal neural structure. Despite the few side-effects reported by clinical studies, the assessment of potential localized temperature increases in tissues is still not solved. In this study, the temperature increase induced by a 3 mA stimulation in the tissue target (i.e., the spinal cord), in its surrounding tissues and in other tissues possibly more vulnerable to temperature increase were assessed through a computational approach. That solves Laplace equation and BioHeat equation for electric field and temperature distribution, respectively, on six whole body high resolution anatomical models, including three models of pregnant women at different gestational ages. Results show that temperature increase distribution in those targets is guided by a complex interaction between different mechanism in which electric stimulation plays a secondary role, in particular when blood perfusion is active. The very low heating assessed (below 1.5 m °C) is not consistent with the hypothesis that the induced temperature increase would critically activate metabolic changes in the target tissues here considered or would contribute to the few side effect that the applications of spinal direct current stimulation protocols have shown.