A Randomized Double-Blind Active-Controlled Crossover Trial of Respiratory-Gated Versus Non-Gated Transcutaneous Auricular Vagus Nerve Stimulation for the Treatment of Motor and Non-Motor Symptoms in Parkinson's Disease

A Randomized Double-Blind Active-Controlled Crossover Trial of Respiratory-Gated Versus Non-Gated Transcutaneous Auricular Vagus Nerve Stimulation for the Treatment of Motor and Non-Motor Symptoms in Parkinson's Disease

The goal of this clinical trial is to compare the effects of different modes and frequencies of transcutaneous auricular vagus nerve stimulation (taVNS) on motor and non-motor symptoms in people with Parkinson's disease. The main questions it aims to answer are:

Which mode and frequency of taVNS is most effective in improving motor or non-motor symptoms? Are there any side effects or safety concerns with different taVNS frequencies? Researchers will compare three types of taVNS: 25 Hz non-expiratory gated, 25 Hz expiratory gated, and 100 Hz expiratory gated stimulation.

Participants will:

Receive each type of taVNS in three 2-week cycles, with 2-month breaks between cycles Undergo neuropsychological assessments, imaging, eye-tracking, and biological sample collection before and after each cycle.

This study employs a three-cycle crossover design to compare the effects of three different modes and frequencies of transcutaneous auricular vagus nerve stimulation (taVNS). The interventions include: 25 Hz non-expiratory gated taVNS, 25 Hz expiratory gated taVNS, and 100 Hz expiratory gated taVNS. Participants will be randomly assigned to one of three groups, with each group receiving a different intervention during each cycle, lasting 2 weeks per cycle. A 2-month washout period will be implemented between cycles to eliminate any carryover effects.The study design will include neuropsychological assessments, imaging, eye-tracking data collection, and biological specimen collection before and after each intervention.

Inclusion Criteria:

• Age: 40 years or older.
• Confirmed diagnosis of Parkinson's disease (PD) per the United Kingdom Brain Bank Criteria by a neurologist specialized in movement disorders.
• Participants must be on a stable dose of all medications for at least 2 weeks, with no planned adjustments to anti-PD medications for the next 3 months.
• In the second version of the Non-Motor Symptoms Scale (NMSS-2) for Parkinson's disease, a score of ≥1 is assigned to either question 4 or question 8.
• Participants must be in good mental health and capable of completing behavioral tests and transcutaneous auricular vagus nerve stimulation.

Exclusion Criteria:

• Mini-Mental State Examination (MMSE) score <24.
• History of head injury, stroke, or other neurological disorders.
• Includes implanted cardiac pacemakers post-DBS operation, local infections, ear loss, or metal implants at the stimulation site.
• Current use of nonsteroidal anti-inflammatory drugs (NSAIDs) or corticosteroids.
• Inability to complete follow-up assessments.