Ameliorating Effects and Mechanisms of TaVNS on Constipation in PD Patients.

Ameliorating Effects and Mechanisms of Transcutaneous Auricular Vagus Nerve Stimulation on Constipation in Parkinson's Disease Patients: a Randomized, Double-blind Clinical Trial

The investigators intend to conduct a randomized, double-blind, sham-stimulation-controlled experiment, incorporating various clinical scales, gastrointestinal electrogram, and high-resolution anorectal manometry (HRAM), to investigate the improvement effect of taVNS on constipation symptoms in PD patients.

The investigators intend to conduct a randomized, double-blind, sham-stimulation-controlled experiment, incorporating various clinical scales, gastrointestinal electrogram, and high-resolution anorectal manometry (HRAM), to investigate the improvement effect of taVNS on constipation symptoms in PD patients. Meanwhile, the investigators aimed to verify mechanistic effects by investigating changes in proteins and cytokines related to inflammation and intestinal barrier function in serum and feces to verify mechanistic effects.

Inclusion Criteria:

1. aged 40-70 years;
2. had a PD diagnosis designated by movement disorder neurologists (Ke-zhong Zhang and Yong-sheng Yuan) according to Movement Disorder Society Clinical Diagnostic Criteria;
3. fulfilled Rome IV criteria for functional constipation, including having < 3 spontaneous bowel movements (SBM; i.e., not induced by rescue medication) per week for the past 3 months with symptom duration of at least 6 months;
4. stable initiation of PD medications, leastways 3 month before this investigation; (5) provided written informed consent.

Exclusion Criteria:

1. a history of previous abdominal surgery (other than appendectomy);
2. the presence of carcinoma;
3. any organic diseases causing constipation or neurologic diseases such as multiple sclerosis, rachischisis, or spinal cord injury;
4. taking antidepressant agents including tricyclic antidepressants and selective serotonin reuptake inhibitors;
5. a serious concomitant disease of the heart, liver, kidney, or diabetes;
6. pregnancy or lactation;
7. participating in another trial or enrolled in a trial during the past month;
8. an allergic reaction to surface electrodes.