Ear-worn nerve stimulator cuts heavy menstrual bleeding in small pilot trial

Heavy menstrual bleeding affects more than 10 million adolescents and adults in the United States, driving missed work, disrupted family life and, for some women, an underlying bleeding disorder such as von Willebrand disease. Current treatments, which range from hormonal medications to surgery, are frequently not tolerated or not acceptable to patients, leaving what researchers describe as an unmet need for non-invasive, non-pharmaceutical options. A new pilot study now reports that a wearable neurostimulation device with a redesigned ear electrode was associated with substantially less menstrual blood loss in a small group of women followed over three consecutive cycles.

The trial, published in Bioelectronic Medicine, tested a configuration of transcutaneous auricular neurostimulation, or tAN, that moves the key stimulating electrode from the cymba concha, a depression inside the ear that has been the standard target, to the mastoid process, the bony prominence behind the auricle. Both sites are innervated by the auricular branch of the vagus nerve, and prior work suggests stimulation at the mastoid can engage the same fibers. The redesign was motivated by complaints in an earlier trial, where some participants reported discomfort or difficulty placing the cymba concha electrode, particularly those with smaller or variable ear anatomy.

The rationale traces back to what researchers call the neural tourniquet. Electrical stimulation of the vagus nerve has been shown in preclinical models of soft tissue injury, including hemophilia A, to reduce bleeding times and shed blood volume. Translational studies have since shown that tAN can modulate platelet phenotype in healthy volunteers, apparently by raising intracellular calcium so platelets respond more readily to pro-coagulant triggers. In a previous open-label study of women with heavy menstrual bleeding, tAN delivered through a cymba concha electrode was associated with significant reductions in menstrual blood loss and symptoms.

In the new study, an open-label, single-arm, decentralized trial registered as NCT06814028 and conducted between February and August 2025, the team screened 40 potential participants. Eleven women qualified, based on a menorrhagia screening tool and a baseline pictorial blood loss assessment chart score above 150, and all were included in the analysis. Most were in their thirties, were Black or of mixed race, had a body mass index of 30, and typically menstruated for seven days. The protocol was approved by a central institutional review board, and participants were followed remotely without in-person clinic visits.

The design used each participant as her own control. During the first menstruation, baseline blood loss was measured daily with the validated PBAC, a semi-quantitative tool that scores used pads and tampons against graded illustrations, with a total score above 100 corresponding to the classical 80-milliliter definition of heavy bleeding. During the second menstruation, participants self-administered two one-hour stimulation sessions daily; during the third, they used a single two-hour session per day. The device, a Sparrow Link patient controller connected to an earpiece, delivered 30 Hz stimulation at the mastoid electrode targeting the vagal branch and 100 Hz at the auriculotemporal region, with participants adjusting intensity until stimulation was perceivable but not painful.

The results showed a clear pattern favoring the longer single session. Mean PBAC scores fell 29 percent during the twice-daily regimen, from a baseline of 513 to 366, a change that narrowly missed statistical significance at p = 0.06. During the once-daily two-hour regimen, scores fell 48 percent, to 268, which was statistically significant compared with both baseline (p = 0.03) and the twice-daily month (p = 0.02). Three participants recorded PBAC scores below 100 in the third cycle, meaning they no longer met the threshold for heavy menstrual bleeding while using the device. Duration of menstruation, derived from the daily product logs, shortened by 10 percent in the second cycle and by 21 percent in the third (p = 0.003).

Symptom and quality-of-life measures moved in the same direction. Cox Menstrual Symptom Scale scores, covering 18 symptoms of dysmenorrhea across pain, gastrointestinal and neurocognitive domains, fell 31 percent during the twice-daily month and 68 percent during the once-daily month, with significant reductions in both symptom severity and frequency. On the RAND-36 health survey, social functioning improved significantly in the second cycle, and role limitations due to emotional problems, pain and general health improved in the third. Participants also reported spending 69 percent less extra time in bed because of menstrual symptoms during the third cycle, an average drop from 9.4 hours to 2.6 hours.

Usability was a central goal of the redesign, and here the results were striking. All eleven participants assigned high satisfaction scores, with a mean of 37 on a 0-to-40 scale, 11 on a 0-to-12 ambulatory usability scale and 15 on a 0-to-16 rating of the patient controller. Only one participant rated the earpiece at a moderate rather than high satisfaction level, a marked contrast with the earlier cymba concha trial, in which a quarter of participants gave only moderate scores and one withdrew over electrode dissatisfaction. Device logs showed 14 of 20 treatment menstruations met an 80 percent compliance threshold, and 71 percent of those compliant cycles achieved at least a 20 percent reduction in PBAC scores, compared with 33 percent of non-compliant cycles.

Safety findings were reassuring but limited. One device-related adverse event was recorded, mild skin irritation and sensitivity attributed to electrode adhesiveness, which resolved without medical attention and was graded as mild. No serious adverse events occurred during the study period. The authors note that no thrombosis-related adverse events have been reported in studies of auricular neurostimulation, including implanted vagus nerve stimulation devices, though they acknowledge that longer and larger studies will be needed to fully characterize the safety profile.

The investigators are careful about the study’s limits. With eleven participants, one baseline cycle instead of the two to three used in most trials, heterogeneous concomitant therapies, no sham control and an open-label design, the results cannot distinguish true therapeutic benefit from placebo effect or natural cycle-to-cycle variability. The PBAC itself has been validated for treatment effect in only one heavy menstrual bleeding population and can underestimate loss with highly saturated products, and minimal clinically important differences have not been established for the symptom and quality-of-life instruments used. Why the single longer session outperformed two shorter ones also remains unresolved; the authors suggest possible accumulation of effect across cycles, differences in stimulation timing relative to circadian rhythms, or longer stimulation producing more primed platelets, and they call for larger, blinded, sham-controlled trials with laboratory assessments of platelet function before the approach can be considered an established treatment.

Subject of Research: Transcutaneous auricular neurostimulation with a novel mastoid electrode configuration for heavy menstrual bleeding

Article Title: A novel transcutaneous auricular neurostimulation electrode configuration for treatment of heavy menstrual bleeding: an open-label trial

Article References: Czura, C. J., Weyand, A. C., Baldwin, M. K., Recht, M., Benner, C. G., Harada, K., Wade, B. L., Luellen, M., Darrow, M. J., McWade, M. A., Covalin, A., & Khodaparast, N. (2026). A novel transcutaneous auricular neurostimulation electrode configuration for treatment of heavy menstrual bleeding: an open-label trial. Bioelectronic Medicine, 12(1), Article 10. https://doi.org/10.1186/s42234-026-00203-1

Image Credits: AI Generated

DOI: 10.1186/s42234-026-00203-1

Keywords: heavy menstrual bleeding, transcutaneous auricular neurostimulation, vagus nerve, neural tourniquet, PBAC, pilot trial, neuromodulation, platelets, menstrual symptoms, medical device, open-label study, hemostasis