Optimization of taVNS Intervention Strategies for Refractory Constipation

Inclusion Criteria (Revised) Diagnosis of Functional Constipation (FC): Meets Rome IV criteria for functional constipation. Low CSBM frequency during screening: During the 2-week screening/run-in period, has ≤2 complete spontaneous bowel movements (CSBMs) per week, based on daily diary. Inadequate response to prior therapy: History of ≥3 months of prior constipation treatment (e.g., laxatives and/or prokinetic agents) with inadequate response (persistent constipation symptoms and/or persistently low CSBM frequency) as documented by medical history and/or records. Age: 18 to 80 years. Ability to comply: Able and willing to comply with study procedures (including stimulation sessions and diary completion). No concurrent clinical trial participation: Not participating in another interventional clinical trial during the study period. Informed consent: Provides written informed consent. Exclusion Criteria (Revised) Organic/secondary causes of constipation: Evidence or history of gastrointestinal organic disease (e.g., inflammatory bowel disease, colorectal tumor, congenital megacolon) or other conditions likely to cause secondary constipation, including endocrine/metabolic disorders (e.g., uncontrolled hypothyroidism, uncontrolled diabetes) or neurological disorders (e.g., Parkinson's disease, spinal cord disorders). Medications causing constipation (unless stable): Current use of medications known to cause constipation (e.g., opioids, anticholinergics) that cannot be discon…