Best Parameters for Magnetic Stimulation of the Facial Nerve to Improve Cerebral Blood Flow
Magnetic stimulation of the vasomotor component of the facial nerve has been shown to be effective in significantly increasing cerebral blood flow (CBF) in various animal models. With the intention of eventually developing a clinical, non-invasive, magnetic stimulation device to increase cerebral blood flow as a treatment for ischemic stroke (IS), we first need to understand the relationship between stimulation power, duration and the resulting physiological response. The ideal stimulation parameters are those that maximize the effect on CBF in both magnitude and duration, while minimizing the applied power needed, thereby minimizing patient risk, discomfort, and equipment requirements. We performed experiments in Yorkshire pigs, modifying the power and the stimulation time, and measuring the corresponding effect on brain perfusion as measured by gadolinium contrast-enhanced MRI. We also looked at the effect of repeated stimulation. Perfusion scans were obtained before stimulation, and at 30 minute intervals after stimulation. We observed the perfusion index with 2, 3.5 and 5 minutes of stimulation duration (rapid pulse trains of 10 pulses per second), and at 65%, 80% and 95% of stimulation power. We found that we obtained an average increase of about 70% in perfusion index over baseline after a single stimulation train, lasting more than two hours and returning to normal after four hours. We observed no significant difference in response with any of the stimulation parameters tested, confirming that we get a very effective response at 65 power and 2 minutes, but suggesting the minimum power and duration needed is even lower than the parameters tested. Repeated stimulation caused the same effect as the first stimulation in every pig tested.
KeywordsPerfusion MRI cerebral blood flow magnetic stimulation facial nerve geniculate ganglion
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