Vagus Nerve Stimulation in Peripheral Targets

Although vagus nerve stimulation (VNS) is nowadays frequently used in the treatment of neuropsychiatric disorders including epilepsy, depression, and chronic pain such as migraine, an increasing number of studies mention its peripheral effects. Central effects of VNS as a cranial neuromodulation method can be prioritized, but it can cause physiological changes in many peripheral organs as well by the autonomic nervous system (ANS) activity modification. It can be argued that the peripheral effects of VNS can occur through many mechanisms such as reducing hyperinflammation, regulating circulation, determining the level of muscle tone, and controlling endocrine and exocrine secretions. In addition, the role of the vagus nerve on the gut-brain axis should always be kept in mind. However, the wide distribution of the vagus nerve and its extensive connections including those in the central nervous system complicate our understanding of its peripheral effects. VNS appears to have effects on the body (metabolism, neuronal activity, immune status, etc.) but we need more randomized placebo-controlled studies to fully understand and demonstrate the effects of VNS on peripheral targets. Biofeedback systems can be useful both for testing different stimulation parameters and for better understanding of peripheral effects.