Effects of Transcutaneous Tibial and Auricular Vagus Nerve Stimulation in Females With Primary Dysmenorrhea

Primary dysmenorrhea is one of the most prevalent menstrual disorders among young females and is associated with significant pain, functional limitations, absenteeism, and increased use of analgesic medications. Current management primarily relies on non-steroidal anti-inflammatory drugs (NSAIDs), which may not provide adequate relief for all individuals and can produce adverse effects with repeated use. Therefore, effective non-pharmacological interventions are needed.

Transcutaneous Tibial Nerve Stimulation (TTNS) and Transcutaneous Auricular Vagus Nerve Stimulation (taVNS) are non-invasive neuromodulation techniques that have demonstrated promising effects in reducing pain and regulating autonomic nervous system activity. While each intervention has been investigated separately for various pain conditions, evidence regarding their comparative effectiveness and the potential benefit of combining both interventions in females with primary dysmenorrhea remains limited.

This study is a randomized, parallel-group, assessor-blinded controlled trial. Approximately 66 participants with primary dysmenorrhea will be recruited using consecutive sampling and randomly allocated using computer-generated block randomization into one of four groups:

TTNS group, taVNS group, Combined TTNS + taVNS group Sham stimulation group

Participants will receive their allocated intervention according to standardized treatment protocols. The assessor responsible for outcome measurements will remain blinded to group allocation.

The primary outcomes are pain intensity and autonomic function. Secondary outcomes include menstrual symptoms and NSAID consumption. Outcome assessments will be conducted at baseline and after completion of the intervention period.

The findings of this study are expected to provide evidence regarding the effectiveness of TTNS, taVNS, and their combined application as safe, non-invasive treatment options for the management of primary dysmenorrhea and may contribute to improving conservative physiotherapy management of this condition.

• Transcutaneous Tibial Nerve Stimulation (TTNS) (Device): Electrical stimulation will be delivered through a TENS device using surface electrodes placed over the posterior tibial nerve for 30 mins according to the study protocol for the management of primary dysmenorrhea. The intervention will be applied for 5 consecutive days, including 2 days before and 3 days during the mensturation period.
• Transcutaneous Auricular Vagus Nerve Stimulation (TaVNS) (Device): Electrical stimulation delivered through a TENS device using surface electrodes placed on the auricular branch of the vagus nerve for 30 mins according to the study protocol for the management of primary dysmenorrhea. The intervention will be applied for 5 consecutive days, including 2 days before and 3 days during the mensturation period.
• TTNS+TaVNS (Device): Electrical stimulation delivered through a TENS device to both the posterior tibial nerve and the auricular branch of the vagus nerve sequentially according to the study protocol. The intervention will be applied for 5 consecutive days, including 2 days before and 3 days during the mensturation period.
• Sham Stimulation (Device): Sham stimulation delivered using the same TENS device and electrode placement as the active intervention but without therapeutic electrical stimulation. The intervention will be applied for 5 consecutive days, including 2 days before and 3 days during the mensturation period.

Primary outcomes

• Dysmenorrhea Severity - WaLIDD Score [Baseline, 4th Week, 8th Week , and 12th Week]: Dysmenorrhea severity will be assessed using the WaLIDD score. The WaLIDD score is a multidimensional assessment of dysmenorrhea severity based on the number of pain days, pain intensity, work/activities affected, and history of dysmenorrhea. The total score ranges from 0 to 12, with higher scores indicating greater dysmenorrhea severity.
• Pain Intensity - Numeric Pain Rating Scale (NPRS) [Baseline, 4th Week, 8th Week , and 12th Week]: Pain intensity will be assessed using the Numeric Pain Rating Scale (NPRS), ranging from 0 (no pain) to 10 (worst possible pain). NPRS will be recorded immediately before and immediately after each treatment session during the 5-day intervention period of each menstrual cycle.
• Autonomic Function - Heart Rate Variability (RMSSD) [Baseline, 4th Week, 8th Week , and 12th Week]: Autonomic function will be assessed using the root mean square of successive differences (RMSSD) derived from heart rate variability. RMSSD will be reported in milliseconds (ms), with changes from pre-treatment to post-treatment used to evaluate autonomic response.
• Autonomic Function - Heart Rate Variability (LF/HF Ratio) [Baseline, 4th Week, 8th Week , and 12th Week]: Autonomic function will be assessed using the low-frequency to high-frequency (LF/HF) ratio derived from heart rate variability. The LF/HF ratio will be used to evaluate changes in cardiac autonomic activity in response to the intervention.

Secondary outcomes

• Menstrual Symptoms - Menstrual Distress Questionnaire (MEDI-Q) Score [Baseline, Week 4, Week 8 and Week 12]: Menstrual-related symptoms will be assessed using the Menstrual Distress Questionnaire (MDQ). The questionnaire evaluates the severity of menstrual symptoms across multiple symptom categories. Higher scores indicate greater menstrual symptom severity.
• NSAID Consumption [Baseline, Week 4, Week 8 and Week 12.]: NSAID consumption will be assessed using a participant diary/log to record the frequency and quantity of NSAID use during each menstrual cycle.

Sex: Female, ages: 14 Years to 30 Years

Inclusion Criteria:

* Nulliparous females aged 14-30 years.
* Regular menstrual cycles.
* Diagnosed with primary dysmenorrhea.
* Pain located in the suprapubic area, abdomen, lower lumbar region, perineum, and/or medial aspect of the thighs during at least half of the annual menstrual cycles or the last three menstrual cycles.
* Pain intensity greater than 4 on the Numeric Pain Rating Scale (NPRS).

Exclusion Criteria:

* Females diagnosed with secondary dysmenorrhea (e.g., endometriosis, ovarian cysts).
* Intrauterine device (IUD) users.
* Presence of skin lesions, scars, or erosions on the inner aspect of the ankle.
* Severe mental disorders (e.g., schizophrenia, bipolar disorder).
* Pacemaker or other implanted electrical devices, if applicable to the stimulation

• Bashir L, Budhlakoti N, Pradhan AK, Sharma D, Jain A, Rehman SS, Kondal V, Jacob SR, Bhardwaj R, Gaikwad K, Mishra DC, Pandey A, Kaur S, Bhati PK, Singh R, Singh GP, Kumar S. Identification of quantitative trait nucleotides for grain quality in bread wheat under heat stress. Sci Rep. 2025 Feb 24;15(1):6641. doi: 10.1038/s41598-025-91199-2. PMID 39994446
• McKiernan P, Baker E, Baker M. Bloodless Medicine in Patients Undergoing Allogeneic Hematopoietic Stem Cell Transplantation. Clin J Oncol Nurs. 2024 Sep 17;28(5):463-468. doi: 10.1188/24.CJON.463-468. PMID 39324711

• Huma Riaz, PhD, Study chair, Riphah International University, Faculty of Rehabilitation & Allied Health Sciences