Neuroprotective Effects of Long-term TaVNS in Early Parkinson's Disease Patients

Inclusion Criteria: 1. Age 55-75 years. 2. Clinically diagnosed Idiopathic Parkinson's disease patients according to the 2016 Chinese diagnostic criteria for Parkinson's disease. 3. Hoehn and Yahr (H\&Y) stage ≤ 2.5 at medication initiation. 4. Parkinson's disease duration ≤ 3 years. 5. Receiving standard anti-Parkinson's disease medication treatment. Exclusion Criteria: 1. Patients with cognitive impairment (MMSE \< 24 and/or MoCA \< 26) or mental illnesses, or those unable to cooperate for other reasons. 2. Use of neuroprotective medications within 90 days prior to baseline, including monoamine oxidase B inhibitors (rasagiline, selegiline), certain dopamine receptor agonists (ropinirole), and GLP-1 receptor agonists such as Exenatide and NLY-01. 3. Use of any medications that may affect dopamine metabolism and/or dopamine receptors within 90 days prior to baseline, including typical and atypical antipsychotics, metoclopramide, α-methyl-dopa, flunarizine, apomorphine, amphetamine derivatives, bupropion, buprenorphine, cocaine, meperidine, methamphetamine, norephedrine, phentermine, modafinil, methylphenidate, procyclidine, reserpine, phenylpropanolamine, or MAO-A inhibitors. 4. Previous treatment with vagus nerve stimulation. 5. MRI contraindications (e.g., claustrophobia unresponsive to comfort or low-dose anxiolytics, dental implants) or MRI scans indicating clinically significant abnormalities in the brain, including but not limited to past hemorrhages or infarcts \> 1 cm³ or \> 3 lacunar infarcts. 6. Contraindications for taVNS, such as patients with cardiac pacemakers or a history of DBS surgery, or those planning surgery during the trial; ear conditions, such as tympanic membrane perforation. 7. Atypical or secondary Parkinsonian syndromes, including but not limited to those caused by trauma, brain tumors, infections, cerebrovascular diseases, or other neurological disorders, or symptoms confirmed by the investigator as drug, chemical, or toxin-related. 8. Previous history of stroke or intracranial mass lesions. 9. Patients with existing or potential cardiovascular diseases. 10. Ophthalmic diseases affecting eye movements. 11. Any neurological disorders other than Parkinsonian motor symptoms that interfere with gait or balance (e.g., chronic pain) or musculoskeletal injuries (e.g., fractures, stroke sequelae). 12. Severe organic diseases, such as late-stage tumors, with a life expectancy of less than 2 years. 13. Concurrent participation in other clinical trials. 14. Inability to receive the required treatment and follow-up due to geographic reasons. 15. Any subject with an upper limb UPDRS tremor score of 3 or higher. 16. Patients with a history of PD-related freezing episodes or falls.