An Efficient Circuit for Pulsed Magnetic Neural Stimulation

Pulse stimulation of peripheral nerves (PNS) is extensively used in the diagnosis of nerve abnormalities and can be applied for pain mitigation and to promote nerve regrowth. Nerve stimulation via magnetic pulses can provide advantages over conventional electrical stimulation; it obviates the need for electrode contact with the skin and is typically less painful. This work contributes to the development of compact and portable systems for magnetic PNS (M-PNS). To date, M-PNS has largely employed pulse generation systems developed for repetitive transcranial magnetic stimulation (rTMS). A new circuit is demonstrated to generate pulsed magnetic fields that increases induced electric (E) field intensities over those attainable in conventional rTMS systems. The resultant E-field has a shortened duration. The required external voltage input is below 300 V. A compact circuit implementation produced peak E-fields of 280 V/m at 1.5 cm distance from the magnetic coil, in 23 μs pulses (while 70-280 μs pulses are typically used for rTMS). Although threshold E fields for neural excitation increase with shorter pulse widths, neural excitation is demonstrated in human subjects via ulnar nerve stimulation and electromyography. This circuit technique may facilitate greater feasibility and flexibility in the design of miniaturized and portable PNS medical devices.