Non-invasive vagus nerve stimulation for primary headache: A clinical update

Background: Non-invasive vagus nerve stimulation (nVNS) is a proven treatment for cluster headache and migraine. Several possible mechanisms of action by which nVNS mitigates headache have been identified. Methods: We conducted a narrative review of recent scientific and clinical research into nVNS for headache, including findings from mechanistic studies and their possible relationships to the clinical effects of nVNS. Results: Findings from animal and human studies have provided possible mechanistic explanations for nVNS efficacy in headache involving four core areas: Autonomic nervous system functions; cortical spreading depression inhibition; neurotransmitter regulation; and nociceptive modulation. We discuss how overlap and interplay among these areas may underlie the utility of nVNS in the context of clinical evidence supporting its safety and efficacy as acute and preventive therapy for both cluster headache and migraine. Possible future nVNS applications are also discussed. Conclusion: Significant progress over the past several years has yielded valuable mechanistic and clinical evidence that, combined with the excellent safety and tolerability profile of nVNS, suggests that it should be considered a first-line treatment for both acute and preventive treatment of cluster headache, an effective option for acute treatment of migraine, and a highly relevant, practical option for migraine prevention.