The basics of VNS:
VNS is a form of stimulation whereby electricity is applied to the vagus nerve to modulate the central nervous system. The Vagus nerve is the 10th cranial nerve, which runs from the brainstem, through the neck, down to the abdomen. Like DBS, VNS is done by surgically implanting a neurostimulator in the chest, while running a wire around the left vagus nerve. (Efferent heart fibers exist on the right.) During stimulation, pulses of electricity are applied twice per minute for 3-5 minutes. Transcutaneous VNS (tVNS) is an even more contemporary technique being explored, but it is currently not approved for clinical purposes in the United States. The vagus nerve is largely a deep and difficult nerve to stimulate through the skin, but in the postulated tVNS technique, its sensory auricular branch may be exploited (in the outer ear). The mechanisms behind VNS’s alterations in the CNS are still unclear, but two hypotheses include: (1) Norepinephrine modulation from the solitary tract’s nuclei projection to the locus coeruleus; and (2) Elevated GABA levels and receptor density as observed in patients who experienced VNS.1 VNS is predominantly being explored in epilepsy and depression, although researchers are also now studying its use in multiple sclerosis, pain, and alzheimer’s disease. More recently, VNS has been explored as an electrical means to reduce inflammation, and shows promise in rheumatoid arthritis and other inflammatory diseases.2 WebMD lists temporary coughing and shortness of breath as side-effects of stimulation.
1Ghanem, T., & Early, S. V. (2006). Vagal nerve stimulator implantation: an otolaryngologist’s perspective. Otolaryngology-Head and Neck Surgery,135(1), 46-51.
2 Tracey, K. J. (2007). Physiology and immunology of the cholinergic antiinflammatory pathway. The Journal of clinical investigation, 117(2), 289-296.