Transcutaneous Vagus Nerve Stimulation for Parkinson's Disease: A Systematic Review and Meta-Analysis

Background: Transcutaneous vagus nerve stimulation (tVNS) is a new, noninvasive therapy being explored for advanced Parkinson’s disease (PD). However, there hasn’t been a thorough analysis of its effects. Objectives: This review looked at how well tVNS improves motor function, affects other symptoms, and its safety under different treatment conditions. Methods: Researchers analyzed six databases for studies where PD patients were treated with tVNS. They focused on motor symptoms (like mobility, balance, and walking) and non-motor symptoms (like cognition, emotions, sleep, and patient-reported outcomes). Safety was also reviewed. Studies were assessed for bias, and data was analyzed using specialized software. Results: Six studies with 176 PD patients were included. tVNS significantly improved some motor symptoms (like motor sign severity, gait, and patient-reported outcomes) when used with medication. However, it worsened verbal fluency, sleep issues, and fatigue under the same conditions. No major side effects were reported. Conclusion: tVNS appears to be a relatively safe add-on treatment for PD with small to moderate benefits for motor symptoms. However, it may negatively affect some non-motor symptoms. The quality of evidence is low, so more research is needed.