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The purpose of this paper is to evaluate the response of the spinal cord, the transmembrane potential, during lumbar magnetic stimulation, using a figure of eight coil.

In order to obtain a precise stimulation of the spinal cord and not the nearby nervous fibres, the coil from the electric circuit of the magnetic stimulator is optimized. The new proposed design is based on the turns’ placement inside the coil, the number of turns required to produce activation. Once the coil configuration is established, the paper addresses other issues that need to be solved: reducing power consumption (the low efficiency of power transfer from the coil to the tissue is a major drawback) and reducing coil heating.

The traditional commercial coils, used for magnetic stimulation in some preliminary experiments, had proved their inability to specifically stimulate the target tissue, without activating the surrounding areas and the low efficiency of power transfer from the coil to the nervous tissue. A more realistic modelling of the stimulating coil, based on the distribution of turns inside the coil can lead to directly stimulation of the spinal cord, during lumbar magnetic stimulation.

If the electrical circuit of the magnetic stimulator is improved, the direct stimulation of the spinal cord is obtained; so, this technique could facilitate functional motor activities, including standing and stepping in paralyzed people, without requiring implantation of electrodes like in electrical stimulation.

The authors underlined that the spinal cord stimulation can be achieved by magnetic stimulation, only if the parameters of the stimulator circuit are optimized. Therefore an original and realistic modelling of the inductive coil was proposed based on number and turns’ distribution within the coil. The coil is designed so that reducing the excessive heating makes it difficult in obtaining a more frequent repetition of stimulus.

The purpose of this paper is to estimate the electrical field induced in the spinal cord and nearby area during lumbar magnetic stimulation.

The spinal cord is modelled as a continuous cylinder, while the vertebral column is also represented by a concentric interrupted cylinder. The coil used for magnetic stimulation is a figure of eight, whose centre is placed above T12‐L1 vertebras. The electrical field is induced and its derivative is computed using the finite difference method.

Preliminary results suggest that magnetic stimulation may be able to induce a sufficiently intense electric field inside the spinal cord, leading to the direct activation of spinal nerve roots.

If the spinal cord can be stimulated directly by magnetic stimulation, this technique can facilitate functional motor activities, including standing and stepping in paralyzed people, in a non‐invasive way.

The authors revealed the fact that functional magnetic stimulation can be applied to the spinal cord, and should be further investigated as an alternative to invasive techniques such as electrical stimulation.