Vagus Nerve and Vagus Nerve Stimulation – Its Role in Chronic Disorders and Therapy Including Impact of Sound

The vagus nerve (VN) is a major component of the parasympathetic nervous system and serves as a bidirectional communication pathway between the brain and visceral organs. It plays an important role in regulating cardiovascular, respiratory, gastrointestinal, endocrine, immune, and inflammatory functions. Chronic diseases are frequently associated with reduced vagal activity, impaired autonomic balance, and increased sympathetic dominance, contributing to inflammation and allostatic stress. Vagus nerve stimulation (VNS) has emerged as a promising neuromodulatory approach for restoring autonomic and neuroimmune balance. While conventional VNS uses implantable devices, non-invasive approaches, particularly transcutaneous auricular vagus nerve stimulation (taVNS), target the auricular branch of the vagus nerve and may provide a safer and more accessible therapeutic option. Emerging evidence also suggests that sound and music may influence autonomic regulation and potentially complement vagal stimulation. This review discusses the anatomy and physiological functions of the vagus nerve, its role in neuroimmune and homeostatic regulation, VNS and taVNS approaches, and the potential relevance of Polyvagal Theory in understanding brain–body communication and chronic disease management.