Simplified Computational Model of the Cervical Region for Transcutaneous Spinal Direct Current Stimulation

Transcutaneous spinal direct current stimulation (tsDCS) is a neuromodulation technique used for the rehabilitation of spinal cord disorders and injuries. Despite its potential effect, the stimulation parameters are not well established, and the underlying effects of tsDCS on the neural mechanisms in the spinal cord remain unknown. A common approach to these problems is the use of computer models to simulate both the electric field in the targeted region and the neural response to the stimulus. Nevertheless, these models are limited, especially for tissues in the cervical region. Thus, this paper presents a model of the volume conductor for the cervical region and optimized simulations using the finite element method in the solution of the current flow problem induced by the application of tsDCS. It was possible to obtain a volume conductor model representing different tissues: skin, subcutaneous fat, muscle, trachea, esophagus, cartilage, vertebral ligaments, vertebrae, vertebral arteries, intervertebral discs, duramater, cerebrospinal fluid, white and gray matter of the spinal cord. Three meshes with different element densities were produced (low, intermediate, and high resolution). The lower density mesh showed an electric field with a mean square error between 6.21% and 2.50% in the spinal cord tissues when compared to the higher resolution mesh. Therefore, the optimization proposed reached acceptable errors and allows multiple simulations, using different setups (conductivities, current intensity, geometric and positions of electrode) with less computational cost (88 min to 17 min for runtime and 4 GB to 800 MB for local storage).