Impact of neuroanatomical variations and electrode orientation on stimulus current in a device for migraine: a computational study

Abstract

Objective. Conventional treatment methods for migraine often have side effects. One treatment involves a wearable neuromodulator targeting frontal nerves. Studies based on this technique have shown limited efficacy and the existing setting can cause pain. These may be associated with neuroanatomical variations which lead to high levels of required stimulus current. The aim of this paper is to study the effect of such variations on the activation currents of the Cefaly neuromodulator. Also, using a different electrode orientation, the possibility of reducing activation current levels to avoid painful side-effects and improve efficacy, is explored. Approach. This paper investigates the effect of neuroanatomical variations and electrode orientation on the stimulus current thresholds using a computational hybrid model involving a volume conductor and an advanced nerve model. Ten human head models are developed considering statistical variations of key neuroanatomical features, to model a representative population. Main results. By simulating the required stimulus current level in the head models, it is shown that neuroanatomical variations have a significant impact on the outcome, which is not solely a function of one specific neuroanatomical feature. The stimulus current thresholds based on the conventional Cefaly system vary from 4.4 mA to 25.1 mA across all head models. By altering the electrode orientation to align with the nerve branches, the stimulus current thresholds are substantially reduced to between 0.28 mA and 15 mA, reducing current density near pain-sensitive structures which may lead to a higher level of patient acceptance, further improving the efficacy. Significance. Computational modeling based on statistically valid neuroanatomical parameters, covering a representative adult population, offers a powerful tool for quantitative comparison of the effect of the position of stimulating electrodes which is otherwise not possible in clinical studies.

Detection of Electrode Proximity to the Cochlea Wall Based on Impedance Variation: a Preliminary Computational Study

“…Numerical methods have been used as a tool to study electrical impedances within the volume conductors. The neuromodulator can be designed and developed using these sophisticated computational methods [5], [8], [13].…”

“…The current passes from the electrode through the surrounding medium and returns to the ground. The electrode-tissue interface contact impedance was assumed to be zero and appropriate continuity conditions were implemented at the boundary of the different domains to provide a unique solution [8].…”

“…In this paper the proximity of the inner cochlea wall to the electrodes, and the effect of tissue parameters [8], [9] by way of impedance measurements, is investigated using computational modes. They are implemented using finite element methods (FEM).…”

Insertion Guidance Based on Impedance Measurements of a Cochlear Electrode Array

“…The outermost layer that surrounds the cochlea was designated as the bony layer. Both automatic and manual segmentation processes were used to obtain a highly efficient and reliable model for simulation (Salkim et al, 2019 ). Smoothing filters utilizing recursive Gaussian, median, and mean filters were employed to allocate each tissue layer in a specific grayscale range.…”

“…The electrode array touched the nearby anatomical layers (as shown in Figure 3 ), and this limited generation of more samples using an anatomical model. An alternative simplified and sufficiently accurate model of the cochlea and adjacent tissue layers can be represented by geometries (i.e., ellipsoids, cylinders) that describe only the regions of interest (Salkim et al, 2019 ). This significantly reduces computation times at the cost of some minor added error, allowing practical multiple measurements.…”