High-Frequency Trans-Spinal Magnetic Stimulation for Chronic Neuropathic Pain Treatment.

Trans-Spinal Magnetic Stimulation (TSMS) is emerging as a promising, low-risk, non-invasive alternative to spinal cord stimulation (SCS) in treating refractory chronic neuropathic back and leg pain. TSMS entails the generation of electrical pulses using a magnetic field produced by a coil positioned on the patient's skin, obviating the need for surgical intervention. Clinical research and trials are continuously needed to assess the effectiveness of TSMS and its potential as a noninvasive option for managing chronic pain.We developed a non-invasive coil allowing for focal TSMS stimulation. The device is based on a new figure-8 ribbon design, ensuring low resistance (R0) and low heating. A system for high-frequency (HF) TSMS pulses (i.e., f=10kHz) was also developed to drive the proposed coil. The coil design was investigated and preliminary tested using the finite element method (FEM) and numerical simulations. Its feasibility was then assessed on rodent experiments using peripheral (i.e., electromyographic-EMG) and central (i.e., brain fMRI) responses to stimulation as endpoints.Numerical simulations showed that action potentials can be generated by TSMS in the peripheral nerves when the coil is driven with high currents (e.g., 10kA). Experimental results revealed that stimulation can penetrate the tissue deeply, reaching the spinal cord and evoking a peripheral nerve response. Changes in the activity of brain areas associated with chronic pain during stimulation were also observed with fMRI.