P084 Electric field distribution in the lumbar spinal cord during trans-spinal magnetic stimulation. Issue 3 (March 2017)

• Record Type: Journal Article
• Authors: Fernandes, S.R.; Salvador, R.; Wenger, C.; de Carvalho, M.; Miranda, P.C.
• Is Part Of: Clinical neurophysiology. Volume 128:Issue 3(2017:Mar.)
• Page Start: e48
• Page End: e50
• Publication Date: 2017-03
• Subjects: Neurophysiology -- Periodicals; Electroencephalography -- Periodicals; Electromyography -- Periodicals; Neurology -- Periodicals; 612.8
• DOI: 10.1016/j.clinph.2016.10.209
• Languages: English
• ISSNs: 1388-2457

Abstract

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: and 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 <100 V/m, not sufficient for stimulating excitable nervous tissue. A different geometry and settings of the magnetic coil may be required for lumbar SC excitation. The two configurations present different E-field directions, which could be useful for specific clinical purposes.