Vagus nerve stimulation: state of the art of stimulation and recording strategies to address autonomic function neuromodulation

Abstract

We report that VNS may benefit from improved stimulation delivery using very advanced technologies. However, most of the results from fundamental animal studies still need to be demonstrated in humans.

Effects of chronic abdominal vagal stimulation of small-diameter neurons on brain metabolism and food intake

“…Second, we did not compare the same current amplitude in S1 and in S2/S3 groups. However, this was done on purpose because currents up to 15 mA for the S1 pattern were unrealistic due to safety and nerve damage concerns (15,19).…”

“…It is likely that an identical cascade is also involved with the S1 stimulation pattern, but to a lesser extent as a consequence of the small number of axons actually stimulated (15). Since the number of axons involved in the generation of action potentials during S1 stimulation represents only a small fraction of the nerve, the activation of the primary brain integrator, i.e., the DVC, may not be strong enough to be detected with PET imaging (35).…”

“…The extend of activated DVC neurons might be so small that it impossible to identify a DVC activation (versus background noise) because of the intrinsic limitations of our present imaging methods (18). Hence the reported absence of activation of the DVC in individuals with vagal stimulation irrespective of the brain imaging method used (15,(19)(20)(21)(22). Conversely, using pulsons, large intensity currents could be applied to the nerve trunk, allowing effective triggering of a neuronal response through a larger amount of small diameter neurons being recruited.…”

“…To do so, more than 20 mA may be needed at this level (15). While they proved to be effective in an acute set-up, these currents are unrealistic in a chronic implant since they generate damages both to the electrode and to the tissues (16).…”

“…Our hypothesis was that the classical stimulation scheme using low intensity, long-lasting current pulses (1-5 mA, 500 to 1000 µs) is unable to activate a large number of abdominal vagal neurons (15). This, in turn, might recruit only a limited number of neurons in the dorsal vagal complex (DVC).…”