The effectiveness of Vagus nerve stimulation in the treatment of Alzheimer’s disease and Parkinson’s disease: a systematic review

Alzheimer’s disease (AD) and Parkinson’s disease (PD) are progressive neurodegenerative disorders with limited disease-modifying treatments. The locus coeruleus (LC), a brainstem nucleus and key source of noradrenaline, is one of the earliest sites of degeneration in both conditions. LC dysfunction contributes to neuroinflammation and cognitive decline. Vagus nerve stimulation (VNS) offers a novel therapeutic approach for these diseases by indirectly activating the LC, enhancing noradrenergic signalling, and reducing neuroinflammatory processes. Two main types of VNS exist:<br/><br/>• Invasive VNS, involving surgical implantation<br/><br/>• Transcutaneous VNS (tVNS), a non-invasive alternative targeting auricular or cervical branches. <br/><br/>VNS may therefore hold promise as a disease-modifying strategy in AD and PD. So we aim to systematically evaluate the effectiveness of VNS in treating AD and PD. The review focuses on both human and animal studies, with particular attention to cognitive, motor, and inflammatory outcomes.