Vagus nerve stimulation (VNS) has become a standard therapeutic option for patients with treatment resistant epilepsy and depression and globally is gaining increasing acceptance. Based on the positive experiences with implantable systems, transcutaneous vagus nerve stimulation (tVNS) was first introduced 20 years ago. The field of tVNS is rapidly expanding since the external stimulation is non-invasive and thus avoids numerous side-effects of invasive VNS; tVNS is easily accessible, less expensive and therefore more readily available than conventional VNS. However, transcutaneous stimulation of the outer ear poses new questions regarding the optimal stimulation site and stimulus parameters as well as the physiology and pathways of transcutaneous auricular VNS. Moreover, therapeutic options and realistically reachable goals of tVNS need to be explored.

During the last 20 years, basic and clinical research has unraveled many of these questions and augmented our understanding of tVNS pathways and physiologic effects. The number of publications increased exponentially within the last three years and continues to grow rapidly. Many questions have been addressed and therapeutic indications beyond the treatment of drug-resistant epilepsy and depression are steadily expanding and continue to be explored.