P084 Electric field distribution in the lumbar spinal cord during trans-spinal magnetic stimulation

Abstract

Introduction Magnetic stimulation (MS) of the peripheral and central nervous system has driven an increasing clinical interest since the 1980’s. Modelling studies of the electric field (E-field) distributions and neuron mathematical models contributed to understand the physical effects underlying MS mechanisms. These results can improve coil design and optimize clinical protocols ( Salvador et al., 2011 ). Objectives The main objective of this study is to calculate the E-field distribution in the lumbar spinal cord (SC) during spinal MS, for clinical applications. Methods A realistic MRI-based human model was built using the MIMICS software (v16, http://www.materialise.com/mimics ). Calculations of the primary E-field were performed with MATLAB (version 2015b, www.mathworks.com ) and the secondary E-field with COMSOL Multiphysics (version 4.3b, www.comsol.com ). The figure-8 coil was based on Magstim’s double 70 mm model and its vertex was located over the T12 spinous process. Two orientations were considered for the coil: PA, postero-anterior; LR, left–right. In the calculation, the time derivative of the current in the coil was set to 61.6 A/(micro s). Results Download : Download high-res image (468KB) Download : Download full-size image and Download : Download high-res image (475KB) Download : Download full-size image show the E-field’s magnitude distribution in the spinal white matter (WM) and grey matter (GM) for PA and LR configurations. For the PA configuration, maximum values of 26.0 and 21.9 V/m are reached in the lumbo-sacral WM and GM, respectively. The E-field is oriented along the caudal-rostral direction. For the LR model, the lower lumbar and sacral SC show the highest values, reaching 15.2 and 11.8 V/m in the WM and GM, respectively. The E-field is oriented along the medial–lateral direction in this region. Conclusion MS of the SC has an E-field magnitude