The effects of coil current directions and waveforms on nerve excitation elicited by magnetic stimulation

The amplitude and latency of compound muscle action potentials (CMAPs) during magnetic stimulation of peripheral nerves depend on the stimulus current direction and waveform. The output waveforms from currently used magnetic stimulators are mono- and polyphasic. The authors analyzed the nerve excitation elicited by four different combinations of coil current waveform/direction. It was shown that the axon is easily excited with biphasic coil current waveform and that the latency depends on coil current waveform, direction and strength. The simulation results are applicable to predict the change of excitation threshold and latency of CMAPs varied with the combination of coil current waveform/direction in magnetic stimulation of human peripheral nerves