Transcutaneous Electrical Nerve Stimulation to Improve Female Sexual Dysfunction Symptoms: A Pilot Study

A Prospective Observational Study of Posterior Tibial Nerve Stimulation in Multiple Sclerosis

INTRODUCTION AND HYPOTHESIS

The objective was to examine the outcomes of posterior tibial nerve stimulation (PTNS) on bladder, bowel, and sexual health-related quality of life among a cohort of patients with multiple sclerosis (MS) with refractory lower urinary tract symptoms (LUTS).

METHODS

Patients with MS and refractory LUTS were recruited for a prospective, observational study using PTNS to treat their symptoms. Patients underwent 12 weekly 30-min PTNS sessions and bladder, bowel, and sexual symptoms were evaluated at baseline, 3, 12, and 24 months with voiding diaries, visual analog scales (VAS), and validated patient-reported questionnaires, including the American Urological Association Symptom Score (AUA-SS), Neurogenic Bladder Symptom Score (NBSS), Michigan Incontinence Symptom Index (M-ISI), Health Status Questionnaire, Sexual Satisfaction Scale, and Bowel Control Scale.

RESULTS

A total of 23 patients were recruited: 18 started PTNS and 14 completed 3 months of PTNS. Of the 18 who started PTNS, the mean age was 52 years (SD 12), 61% were female, 83% were white, and most patients had relapsing remitting (39%) MS. Baseline (n=18) and 3-month voiding (n=11) outcomes showed no significant change in number of voids or incontinence episodes. The median VAS symptom improvement was 49 (IQR 26.5, 26) and 9 (53%) patients elected for monthly maintenance PTNS. On paired analysis, there was a significant improvement in median change in NBSS, AUA-SS, and M-ISI. There was no significant change in bowel or sexual dysfunction.

CONCLUSIONS

This prospective, observational study of PTNS in patients with MS with refractory LUTS shows improvement in patient-reported bladder outcomes, but not in number of voids per day or bowel or bladder function.

Short-Term Dorsal Genital Nerve Stimulation Increases Subjective Arousal in Women With and Without Spinal Cord Injury: A Preliminary Investigation

OBJECTIVES

Female sexual dysfunction (FSD) affects an estimated 40% of women. Unfortunately, FSD is understudied, leading to limited treatment options for FSD. Neuromodulation has shown some success in alleviating FSD symptoms. We developed a pilot study to investigate the short-term effect of electrical stimulation of the dorsal genital nerve and tibial nerve on sexual arousal in healthy women, women with FSD, and women with spinal cord injury (SCI) and FSD.

MATERIALS AND METHODS

This study comprises a randomized crossover design in three groups: women with SCI, women with non-neurogenic FSD, and women without FSD or SCI. The primary outcome measure was change in vaginal pulse amplitude (VPA) from baseline. Secondary outcome measures were changes in subjective arousal, heart rate, and mean arterial pressure from baseline. Participants attended one or two study sessions where they received either transcutaneous dorsal genital nerve stimulation (DGNS) or tibial nerve stimulation (TNS). At each session, a vaginal photoplethysmography sensor was used to measure VPA. Participants also rated their level of subjective arousal and were asked to report any pelvic sensations.

RESULTS

We found that subjective arousal increased significantly from before to after stimulation in DGNS study sessions across all women. TNS had no effect on subjective arousal. There were significant differences in VPA between baseline and stimulation, baseline and recovery, and stimulation and recovery periods among participants, but there were no trends across groups or stimulation type. Two participants with complete SCIs experienced genital sensations.

CONCLUSIONS

To our knowledge, this is the first study to measure sexual arousal in response to short-term neuromodulation in women. This study indicates that short-term DGNS but not TNS can increase subjective arousal, but the effect of stimulation on genital arousal is inconclusive. This study provides further support for DGNS as a treatment for FSD.

Low frequency neuromuscular electrical stimulation applied to the bulbospongiosus muscle prolongs the ejaculation latency in a rat model

Premature ejaculation (PE) is common, but its true pathophysiology is not clear, and treatments are limited. We aimed to investigate the effect of neuromuscular electrical stimulation applied in different modes and frequencies to the bulbospongiosus muscle on ejaculation parameters. In this study, 24 male Wistar albino rats were used. The rats were equally divided into three groups: control, high-frequency burst (HFB) and low-frequency (LF) (n = 8 each). Neuromuscular electrical stimulation was applied to the rats for 30 min. In the HFB group, this stimulation was applied in the burst mode at 80 Hz frequency using 200 microseconds (µs) transition time. In the LF group, manual stimulation was applied using a 2 Hz frequency and 200 µs transition time. Following the intraperitoneal administration of para-chloroamphetamine at a dose of 5 mg/kg, ejaculation time, increase in basal seminal vesicle pressure, seminal vesicle maximum pressure, number and interval time of seminal vesicle contractions and bulbospongiosus muscle electromyography activities were evaluated over 30 min. There was a significant difference between the groups in terms of ejaculation time (p = 0.002). The ejaculation times of the LF, HFB and control groups were 1344.71 ± 105.9, 908 ± 62 and 672 ± 149.7 s, respectively. The post hoc analysis revealed that the ejaculation time of the LF group was significantly longer than that of the HFB and control groups (p = 0.033 and p = 0.001, respectively). The remaining parameters did not differ significantly between the groups. The results showed that low-frequency (2 Hz) electrical stimulation applied to the male rats significantly prolonged the ejaculation time. It is thus considered that applying neuromuscular electrical stimulation before planned sexual activity can prevent the rhythmic contractions necessary for completing the ejaculatory process by maintaining subtetanic continuous contraction and prolonging the ejaculation time in patients with premature ejaculation complaints.

Immediate and Long-Term Effects of Tibial Nerve Stimulation on the Sexual Behavior of Female Rats

OBJECTIVES

There are limited treatment options for female sexual dysfunction (FSD). Percutaneous tibial nerve stimulation (PTNS) has shown improvements in FSD symptoms in neuromodulation clinical studies, but the direct effects on sexual function are not understood. This study evaluated the immediate and long-term effects of PTNS on sexual motivation and receptivity in a rat model of menopausal women. Our primary hypothesis was that long-term PTNS would yield greater changes in sexual behavior than short-term stimulation.

MATERIALS AND METHODS

In two experiments, after receiving treatment, we placed ovariectomized female rats in an operant chamber in which the female controls access to a male by nose poking. We used five treatment conditions, which were with or without PTNS and no, partial, or full hormone priming. In experiment 1, we rotated rats through each condition twice with behavioral testing immediately following treatment for ten weeks. In experiment 2, we committed rats to one condition for six weeks and tracked sexual behavior over time. We quantified sexual motivation and sexual receptivity with standard measures.

RESULTS

No primary comparisons were significant in this study. In experiment 1, we observed increased sexual motivation but not receptivity immediately following PTNS with partial hormone priming, as compared with priming without PTNS (linear mixed effect models; initial latency [p = 0.34], inter-interval latency [p = 0.77], nose poke frequency [p = 0.084]; eight rats). In experiment 2, we observed trends of increased sexual receptivity (linear correlation for weekly group means; mounts [p = 0.094 for trendline], intromissions [p = 0.073], lordosis quotient [p = 0.58], percent time spent with a male [p = 0.39], decreased percent time alone [p = 0.024]; four rats per condition), and some sexual motivation metrics (linear correlation for weekly group means; nose pokes per interval [p = 0.050], nose poke frequency [p = 0.039], decreased initial latency [p = 0.11]; four rats per condition) when PTNS was applied long-term with partial hormone priming, as compared with hormone-primed rats without stimulation.

CONCLUSIONS

PTNS combined with hormone priming shows potential for increasing sexual motivation in the short-term and sexual receptivity in the long-term in rats. Further studies are needed to examine variability in rat behavior and to investigate PTNS as a treatment for FSD in menopausal women.

Effect of knack technique on vaginal laxity in multiparous women: A randomized controlled trial

BACKGROUND

Vaginal laxity defined according to the International Urogynecological Association/International Continence society is excessive vaginal looseness; it is one of the most common symptoms of pelvic floor dysfunction, which refers to medical/functional disorders that can have a significant impact on a woman's sexual self-esteem and sexual life.

AIM

This study aimed to determine the impact of the Knack Technique on Pelvic floor muscle (PFM) and sexual function in women with vaginal laxity.

METHODS

Thirty females complaining of vaginal laxity were randomly chosen from the outpatient clinic at Deraya University. Their ages varied from 35 to 45 years, their body mass index was 25-30 kg/m2, and a number of parities ≤ three normal vaginal deliveries and at least two years from the last delivery complaining about vaginal laxity, water entrapment, and loss of friction during sexual intercourse. They were randomized into two equal groups at random (A, B). Group A (15 females) received (PSTES) and group B (15 females) received (PSTES) and Knack Technique. Both the groups received three sessions per week for 2 months.

EVALUATION

The outcome measures were evaluated through pre- and post-interventions by using ultrasonography imaging to assess PFM function, Sexual Satisfaction Index, and Vaginal Laxity Questionnaires (VLQ) to assess sexual function.

RESULTS

Analysis indicated a significant improvement in vaginal laxity in the two groups. Comparison between groups pre- and posttreatment showed that there was no statistically significant difference between the groups B and A in SSI and VLQ, while there were significant differences between the groups A and B in PFM force.

CONCLUSION

Combining Parasacral transcutaneous electrical stimulation (PSTES) and Knack Technique is more effective than PSTES alone in reducing vaginal laxity as well as improving PFM and sexual function in women with vaginal laxity.

Acute dorsal genital nerve stimulation increases subjective arousal in women with and without spinal cord injury: a preliminary investigation

Introduction

Female sexual dysfunction (FSD) impacts an estimated 40% of women. Unfortunately, female sexual function is understudied, leading to limited treatment options for FSD. Neuromodulation has demonstrated some success in improving FSD symptoms. We developed a pilot study to investigate the short-term effect of electrical stimulation of the dorsal genital nerve and tibial nerve on sexual arousal in healthy women, women with FSD, and women with spinal cord injury (SCI) and FSD.

Methods

This study consists of a randomized crossover design in three groups: women with SCI, women with non-neurogenic FSD, and women without FSD or SCI. The primary outcome measure was change in vaginal pulse amplitude (VPA) from baseline. Secondary outcome measures were changes in subjective arousal, heart rate, and mean arterial pressure from baseline. Participants attended one or two study sessions where they received either transcutaneous dorsal genital nerve stimulation (DGNS) or tibial nerve stimulation (TNS). At each session, a vaginal photoplethysmography sensor was used to measure VPA. Participants also rated their level of subjective arousal and were asked to report any pelvic sensations.

Results

We found that subjective arousal increased significantly from before to after stimulation in DGNS study sessions across all women. TNS had no effect on subjective arousal. There were significant differences in VPA between baseline and stimulation, baseline and recovery, and stimulation and recovery periods among participants, but there were no trends across groups or stimulation type. Two participants with complete SCIs experienced genital sensations.

Discussion

This is the first study to measure sexual arousal in response to acute neuromodulation in women. This study demonstrates that acute DGNS, but not TNS, can increase subjective arousal, but the effect of stimulation on genital arousal is inconclusive. This study provides further support for DGNS as a treatment for female sexual dysfunction.

Tibial nerve stimulation increases vaginal blood perfusion and bone mineral density and yield load in ovariectomized rat menopause model

INTRODUCTION AND HYPOTHESIS

Human menopause transition and post-menopausal syndrome, driven by reduced ovarian activity and estrogen levels, are associated with an increased risk for symptoms including but not limited to sexual dysfunction, metabolic disease, and osteoporosis. Current treatments are limited in efficacy and may have adverse consequences, so investigation for additional treatment options is necessary. Previous studies have demonstrated that percutaneous tibial nerve stimulation (PTNS) and electro-acupuncture near the tibial nerve are minimally invasive treatments that increase vaginal blood perfusion or serum estrogen in the rat model. We hypothesized that PTNS would protect against harmful reproductive and systemic changes associated with menopause.

METHODS

We examined the effects of twice-weekly PTNS (0.2 ms pulse width, 20 Hz, 2× motor threshold) under ketamine-xylazine anesthesia in ovariectomized (OVX) female Sprague-Dawley rats on menopause-associated physiological parameters including serum estradiol, body weight, blood glucose, bone health, and vaginal blood perfusion. Rats were split into three groups (n = 10 per group): (1) intact control (no stimulation), (2) OVX control (no stimulation), and (3) OVX stimulation (treatment group).

RESULTS

PTNS did not affect serum estradiol levels, body weight, or blood glucose. PTNS transiently increased vaginal blood perfusion during stimulation for up to 5 weeks after OVX and increased areal bone mineral density and yield load of the right femur (side of stimulation) compared to the unstimulated OVX control.

CONCLUSIONS

PTNS may ameliorate some symptoms associated with menopause. Additional studies to elucidate the full potential of PTNS on menopause-associated symptoms under different experimental conditions are warranted.

Pudendal, but not tibial, nerve stimulation modulates vulvar blood perfusion in anesthetized rodents

INTRODUCTION AND HYPOTHESIS

Preclinical studies have shown that neuromodulation can increase vaginal blood perfusion, but the effect on vulvar blood perfusion is unknown. We hypothesized that pudendal and tibial nerve stimulation could evoke an increase in vulvar blood perfusion.

METHODS

We used female Sprague-Dawley rats for non-survival procedures under urethane anesthesia. We measured perineal blood perfusion in response to 20-minute periods of pudendal and tibial nerve stimulation using laser speckle contrast imaging (LSCI). After a thoracic-level spinalization and a rest period, we repeated each stimulation trial. We calculated average blood perfusion before, during, and after stimulation for three perineal regions (vulva, anus, and inner thigh), for each nerve target and spinal cord condition.

RESULTS

We observed a significant increase in vulvar, anal, and inner thigh blood perfusion during pudendal nerve stimulation in spinally intact and spinalized rats. Tibial nerve stimulation had no effect on perineal blood perfusion for both spinally intact and spinalized rats.

CONCLUSIONS

This is the first study to examine vulvar hemodynamics with LSCI in response to nerve stimulation. This study demonstrates that pudendal nerve stimulation modulates vulvar blood perfusion, indicating the potential of pudendal neuromodulation to improve genital blood flow as a treatment for women with sexual dysfunction. This study provides further support for neuromodulation as a treatment for women with sexual arousal disorders. Studies in unanesthetized animal models of genital arousal disorders are needed to obtain further insights into the mechanisms of neural control over genital hemodynamics.

Evaluating the effects of transcutaneous tibial nerve stimulation or pelvic floor muscle training on sexual dysfunction in female multiple sclerosis patients reporting overactive bladder

AIMS

Sexual dysfunction (SD) is common in female patients with multiple sclerosis (MS) reporting overactive bladder (OAB) symptoms. The aim of the study was to evaluate the effects of transcutaneous tibial nerve stimulation (TTNS) and pelvic floor muscle training (PFMT) with biofeedback on SD in female patients with MS reporting OAB symptoms.

METHODS

Patients with overactive bladder and SD were allocated to receive TTNS or PFMT daily. Overactive bladder symptoms, sexual functions, and sexual quality of life were assessed at baseline and 6^th weeks. Female Sexual Function Index (FSFI), Overactive Bladder Questionnaire (OABv-8), and Sexual Quality of Life-Female (SQoL-F) questionnaires were used.

RESULTS

Thirty patients (TTNS = 10, PFMT = 20) were included in the study. Compared to baseline, total FSFIOABv-8, and SQoL-F scores improved in both TTNS (p = 0.005, p = 0.011, p = 0.444, respectively) and PFMT (p = 0.002, p = 0.001, p = 0.001, respectively) groups. Between-group comparisons did not show any significant differences.

CONCLUSION

This study demonstrates the efficacy of both TTNS and PFMT for improving sexual function in female MS patients with OAB symptoms, but did not show superiority of any particular method. Further studies are required to investigate the differences between these two non-invasive methods.

Enhanced transcutaneous electrical nerve stimulation achieved by a localized virtual bipole: a computational study of human tibial nerve stimulation

OBJECTIVE

Electrical neuromodulation is a clinically effective therapeutic instrument, currently expanding into newer indications and larger patient populations. Neuromodulation technologies are also moving towards less invasive approaches to nerve stimulation. In this study, we investigated an enhanced transcutaneous electrical nerve stimulation (eTENS) system that electrically couples a conductive nerve cuff with a conventional TENS electrode. The objectives were to better understand how eTENS achieves lower nerve activation thresholds, and to test the feasibility of applying eTENS in a human model of peripheral nerve stimulation.

APPROACH

A finite element model (FEM) of the human lower leg was constructed to simulate electrical stimulation of the tibial nerve, comparing TENS and eTENS. Key variables included surface electrode diameter, nerve cuff properties (conductivity, length, thickness), and cuff location. Enhanced neural excitability was predicted by relative excitability (RE > 1), derived using either the activating function (AF) or the nerve activation threshold (MRG model).

MAIN RESULTS

Simulations revealed that a localized 'virtual bipole' was created on the target nerve, where the isopotential surface of the cuff resulted in large potential differences with the surrounding tissue. The cathodic part (nerve depolarization) of the bipole enhanced neural excitability, predicted by RE values of up to 2.2 (MRG) and 5.5 (AF) when compared to TENS. The MRG model confirmed that action potentials were initiated at the cathodic edge of the nerve cuff. Factors contributing to eTENS were larger surface electrodes, longer cuffs, cuff conductivity (>1×10³ S m^-1), and cuff position relative to the cathodic surface electrode.

SIGNIFICANCE

This study provides a theoretical basis for designing and testing eTENS applied to various neural targets and data suggesting function of eTENS in large models of nerve stimulation. Although eTENS carries key advantages over existing technologies, further work is needed to translate this approach into effective clinical applications.

The rodent vaginal microbiome across the estrous cycle and the effect of genital nerve electrical stimulation

Treatment options are limited for the approximately 40% of postmenopausal women worldwide who suffer from female sexual dysfunction (FSD). Neural stimulation has shown potential as a treatment for genital arousal FSD, however the mechanisms for its improvement are unknown. One potential cause of some cases of genital arousal FSD are changes to the composition of the vaginal microbiota, which is associated with vulvovaginal atrophy. The primary hypothesis of this study was that neural stimulation may induce healthy changes in the vaginal microbiome, thereby improving genital arousal FSD symptoms. In this study we used healthy rats, which are a common animal model for sexual function, however the rat vaginal microbiome is understudied. Thus this study also sought to examine the composition of the rat vaginal microbiota. Treatment rats (n = 5) received 30 minutes of cutaneous electrical stimulation targeting the genital branch of the pudendal nerve, and Control animals (n = 4) had 30-minute sessions without stimulation. Vaginal lavage samples were taken during a 14-day baseline period including multiple estrous periods and after twice-weekly 30-minute sessions across a six-week trial period. Analysis of 16S rRNA gene sequences was used to characterize the rat vaginal microbiota in baseline samples and determine the effect of stimulation. We found that the rat vaginal microbiota is dominated by Proteobacteria, Firmicutes, and Actinobacteria, which changed in relative abundance during the estrous cycle and in relationship to each other. While the overall stimulation effects were unclear in these healthy rats, some Treatment animals had less alteration in microbiota composition between sequential samples than Control animals, suggesting that stimulation may help stabilize the vaginal microbiome. Future studies may consider additional physiological parameters, in addition to the microbiome composition, to further examine vaginal health and the effects of stimulation.

What Is New in Neuromodulation?

Neuromodulation encompassing sacral and peripheral modalities is an established, effective, and safe higher-order treatment option approved in the USA for managing refractory overactive bladder, non-obstructive urinary retention, and fecal incontinence. This review highlights the most recent literature, indications, treatment durability, and the latest innovations in this field. Regarding sacral neuromodulation (SNM), recent work suggests improved parameters for optimal lead placement, increased data to support the lasting effects of treatment, and novel applications of this technology to other pelvic disorders. In addition, there are emerging technologies with smaller MRI compatible devices. Newer data on percutaneous tibial nerve stimulation (PTNS) suggests it may be more beneficial for certain patients. With new technology, implantable tibial nerve stimulators are ushering in a new frontier of nerve stimulation in the comfort of the patient's home.