Sensitivity Analysis of a Numerical Model for Percutaneous Auricular Vagus Nerve Stimulation

Abstract

Background: Less-invasive percutaneous stimulation of the auricular branch of the vagus nerve (pVNS) gained importance as a possible nonpharmacological treatment for various diseases. The objective is to perform a sensitivity analysis of a realistic numerical model of pVNS and to investigate the effects of the model parameters on the excitation threshold for single and bundled axons. Methods: Sim4Life electrostatic solver and neural tissue models were combined for electromagnetic and neural simulation. The numerical model consisted of a high-resolution model of a human ear, blood vessels, nerves, and three needle electrodes. Investigated parameters include the axon diameter and number, model temperature, ear conductivity, and electrodes’ penetration depth and position. Results: The electric field distribution was evaluated. Model temperature and ear conductivity are the non-influential parameters. Axons fiber diameter and the electrodes’ penetration depth are the most influential parameters with a maximum threshold voltage sensitivity of 32 mV for each 1 μm change in the axon diameter and 38 mV for each 0.1 mm change in the electrodes’ penetration depth. Conclusions: The established sensitivity analysis allows the identification of the influential and the non-influential parameters with a sensitivity quantification. Results suggest that the electrodes’ penetration depth is the most influential parameter.

Current Directions in the Auricular Vagus Nerve Stimulation II – An Engineering Perspective

“…Different models for transcutaneous and percutaneous aVNS have been developed, which use multiple electrodes, consider spatiotemporal electric fields, the geometry and properties of embedded nerves (Kuhn et al, 2008; Samoudi et al, 2017, 2019; Kaniusas, 2019). These models allow numerical optimisation not only of an engineering aVNS solution (e.g., its electrode shape and the applied stimulation pattern) but also of the electrophysiological impact (e.g., the percentage of activated axons), and consequently of the potential therapeutic outcome of aVNS.…”

Stimulation Pattern Efficiency in Percutaneous Auricular Vagus Nerve Stimulation: Experimental versus Numerical data

“…1b). Here the auricular tissue conductivity was set to 0.2 S/m while that of embedded vessels to 0.7 S/m, in line with our recent works [41], [42].…”

“…Nerves are modelled as bundles of fibers with a physical volume (given by the fiber diameter, see below) and conductivity (of 1 S/m [32]). A distance equal to the diameter of a single fiber is kept between two adjacent axons to simulate a dense population of axons [42].…”

“…1b. A space equal to the diameter of a single axon is modelled between two adjacent axons to simulate a dense axon population [42].…”

Sensitivity Study of Neuronal Excitation and Cathodal Blocking Thresholds of Myelinated Axons for Percutaneous Auricular Vagus Nerve Stimulation

“…The goal of this study is to assess the influence of different parameters on the excitation and blocking threshold for pVNS by means of numerical stimulation. Although the influence of different parameters, including temperature, electrode position, axon diameter, and pulse type, has already been investigated by [14]- [16], the novelty of this study lies among other things in the fact that parameters are varied simultaneously, giving the possibility to investigate interaction between parameters. This is particularly useful to study how dependency on axon diameter varies for changes of other parameters.…”