Unintended Vagus Nerve Stimulation From Cuff Electrode During MRI: Combined Effects of Gradient and Radiofrequency Fields.

PURPOSE: Emissions generated during magnetic resonance imaging (MRI)-including gradient coil induced electric fields and radiofrequency coil induced heating near nerve fiber-may alter neural activation inside patients. This study investigates the combined effects of these emissions on vagus nerve activation in the presence of cuff electrodes.

METHODS

Electromagnetic, thermal, and neurophysiological simulations were performed to quantify activation thresholds under MRI-induced fields. The study examined the impact of gradient field exposure and RF-induced heating, particularly for the trapezoidal waveform of the gradient coil with short pulse duration.

RESULTS

The results indicate that the presence of the cuff electrode significantly reduces the activation threshold under gradient field exposure, while RF-induced heating further decreases the threshold for stimulations with short pulse durations. In some scenarios, the reduced neuron activation threshold can be lower than peripheral nerve stimulation limits defined in IEC 60601-2-33.

CONCLUSION

These findings indicate the potential risk of unintended vagus nerve stimulation in MRI environments, emphasizing the need for safety considerations in patients with implantable vagus nerve stimulators.