A miniaturized ultra-focal magnetic stimulator and its preliminary application to the peripheral nervous system

Transcranial magnetic stimulation (TMS) is a noninvasive brain stimulation technique used in the clinic to treat several neurological disorders and psychiatric diseases. One of TMS’s significant limitations is its low spatial resolution, which often results in a mismatch between the target area in the brain and the stimulation site on the scalp. To enhance its spatial resolution, we designed and built a complete stimulation system complete with a millimetric-diameter coil and microscopic traces (μCoil). The first tests conducted on healthy volunteers showed that the μCoil stimulation of the radial nerve in the wrist could indeed evoke somatosensory nerve action potentials (SNAPs). In this chapter, we study this nerve stimulation system with electromagnetic and neuron simulators on a neurofunctionalized model from the Virtual Population (ViP v.4) and a μCoil figure-8 geometry. In particular, we study how changes in the μCoil geometry, such as the number of layers, shape, and length of an iron or air core, may help to promote the generation of somatosensory nerve action potentials.