Pelvic Neuromodulation Techniques: A Comparative Overview of Available Methods and Their Applications
Abstract
Pelvic neuromodulation has emerged as a powerful therapeutic modality for managing functional pelvic disorders such as overactive bladder (OAB), chronic pelvic pain (CPP), fecal incontinence, sexual dysfunction,
and neurogenic bladder. While sacral neuromodulation (SNM) remains the most widely recognized approach, newer techniques such as pudendal nerve stimulation (PNM), posterior tibial nerve stimulation (PTNS), and
Genital Nerve Stimulation (GNS) are gaining interest. This review compares these techniques in terms of anatomical target, clinical efficacy, indications, limitations, and future prospects.
1. Introduction
Pelvic disorders such as OAB, urinary retention, and pelvic pain are often refractory to pharmacological treatments. Neuromodulation has been developed to address these limitations by targeting peripheral and central nervous systems. However, despite the promising results, neuromodulation remains underutilized in gynecology.
2. Overview of the different methods
2.1. Sacral Nerve Stimulation (SNM)
Sacral Nerve Stimulation (SNM), also known as sacral neuromodulation, is a minimally invasive therapy that involves the surgical implantation of an electrode near the S3 sacral nerve root, which plays a critical role in the neural control of bladder, bowel, and pelvic floor function. The system delivers mild electrical impulses to modulate the dysfunctional nerve signals between the pelvic organs and the spinal cord.
It is FDA-approved for the treatment of :
• Overactive bladder (OAB) – including symptoms of urgency, frequency, and urge urinary incontinence.
• Non-obstructive urinary retention – to restore the ability to void effectively without anatomical obstruction.
• Fecal incontinence – particularly in cases where conservative treatments have failed.
Strengths:
- Well-established efficacy – Multiple clinical studies and long-term data demonstrate significant improvement in symptoms and quality of life for a majority of patients.
- Reversible and adjustable – The system can be deactivated or removed at any time; stimulation parameters can be individually adjusted to optimize therapeutic effect.
- Effective in both neurogenic and idiopathic conditions – SNM has shown clinical benefit in patients with various underlying causes, including spinal cord injuries, multiple sclerosis, and idiopathic dysfunctions.
Limitations:
• Requires trial stimulation phase – Patients must undergo a temporary test phase (usually 3–14 days) to assess responsiveness before permanent implantation, which may be inconvenient or uncomfortable for some.
• High rates of complications – Common issues include lead migration, local infections, pain at the implant site, loss of efficacy over time, and a considerable rate of revision surgeries.
• Imaging limitations and battery concerns – Older SNM systems are not MRI-compatible, limiting diagnostic options for patients. Battery longevity (typically 3–7 years for non-rechargeable systems) is a concern and may necessitate repeat surgeries for replacement.
2.2. Posterior Tibial Nerve Stimulation (PTNS)
Posterior Tibial Nerve Stimulation (PTNS) is a non-surgical neuromodulation technique that involves electrical stimulation of the posterior tibial nerve, which originates from the same sacral spinal segments (L4–S3) that innervate the bladder and pelvic floor. The stimulation is delivered either percutaneously via a fine
needle electrode inserted near the medial malleolus (ankle le level ) or transcutaneously via surface electrodes.
Indications:
• Overactive bladder (OAB) – PTNS is FDA-approved for the treatment of OAB symptoms such as urinary urgency, frequency, and urge urinary incontinence.
• Urinary urgency/frequency and urge incontinence – Particularly in patients who have failed or cannot tolerate antimuscarinic or β3-agonist medications.
Strengths:
• Minimally invasive, office-based procedure – PTNS can be performed in an outpatient setting without the need for anesthesia or surgical intervention.
• No surgical implantation required – The technique avoids the risks associated with implantable devices and is therefore suitable for patients who prefer non-invasive treatment options or are unfit for surgery.
• Well-tolerated and low-risk – The procedure has a favorable safety profile with minimal side effects, typically
limited to mild skin irritation or transient discomfort at the stimulation site.
Limitations:
• Requires frequent visits – Standard protocol involves weekly sessions over 12 weeks, followed by maintenance
treatments, often every 3–4 weeks. This can be time-consuming and burdensome for many patients.
• Limited long-term efficacy – While short-term symptom improvement is common, sustained therapeutic
benefit often requires ongoing maintenance sessions, and efficacy may decline over time.
• Not effective for neurogenic conditions or chronic pelvic pain – PTNS is not indicated for patients with neurogenic bladder dysfunction (e.g., due to spinal cord injury or multiple sclerosis) or chronic pelvic pain syndromes, where deeper neuromodulation approaches are more appropriate.
Implantable PTNS Devices – e.g., BlueWind™, eCoin™
In response to the limitations of conventional external PTNS, implantable posterior tibial nerve stimulators have been developed (e.g., BlueWind RENOVA™, eCoin™). These miniaturized, battery-powered or externally powered devices are surgically implanted near the posterior tibial nerve, enabling continuous or on-demand neuromodulation without repeated clinic visits.
Advantages of Implantable PTNS Devices:
• Continuous or patient-controlled stimulation – Improves therapy adherence and long-term efficacy.
• Minimally invasive surgical implantation – Often performed under local anesthesia.
• Discreet solution – Eliminates the need for visible electrodes or wearable external units.
• Improved patient comfort – No need for repeated needle insertions or visible electrodes during daily activities.
However, despite these advancements, implantable PTNS systems share certain limitations, especially in comparison to more anatomically secured approaches such as SNM or GNS.
Limitations:
• Very high risk of migration – The electrode is not anchored to a fixed anatomical structure, and due to
its location in an area where patients sit daily, there is a significant risk of device movement and loss of efficacy over time.
• Limited clinical experience and data – Although early results are promising, long-term data and comparative studies are still limited.
• Restricted indications – The implantable PTNS systems are primarily designed for OAB, with limited application in complex conditions such as neurogenic bladder or pelvic pain syndromes.
• Lack of continuous stimulation – External systems often do not provide permanent neuromodulation, requiring manual application and limiting efficacy.
• Visibility and social stigma – The external energy source (often worn at the ankle or knee) may make the patient’s condition noticeable, raising privacy concerns and psychosocial burden.
• Aesthetic and clothing limitations – Wearing a cuff at the knee is impractical for women wearing dresses, and tight jeans may hinder proper device placement or cause discomfort.
• Footwear interference – Devices near the ankle may conflict with fashion choices (e.g., high heels) or sports equipment (e.g., ski boots), reducing daily wearability and compliance.
Conclusion:
While implantable PTNS systems represent a promising evolution beyond conventional external PTNS, challenges such as electrode migration risk, limited efficacy in complex pathologies, and lack of broad clinical experience must be addressed. In parallel, external systems, despite being user-friendly, face considerable practical and social barriers, making sacral or genital nerve stimulation often more suitable for long-term and comprehensive management of pelvic floor dysfunctions.
2.3. Pudendal Nerve Stimulation (PNM)
Pudendal Nerve Modulation (PNM) is an advanced neuromodulation technique that targets the S2–S4 sacral nerve roots, specifically via direct or indirect stimulation of the pudendal nerve, which plays a central role in the innervation of the external urethral and anal sphincters, perineum, and pelvic floor muscles. It offers a more focused approach for pelvic organ function and sensory modulation in the perineal area.
Indications (currently off-label use):
• Urinary and fecal incontinence – Particularly in cases refractory to sacral neuromodulation, with emphasis on improved sphincter control.
• Pelvic pain syndromes – Including pudendal neuralgia, chronic perineal pain, and certain forms of interstitial cystitis/bladder pain syndrome.
• Sexual dysfunction – Especially in cases where nerve-related arousal or sensation deficits are involved.
Strengths:
• More direct control over urethral and anal sphincters – Due to the anatomical proximity of the pudendal nerve to the sphincter musculature, PNM allows precise modulation of continence mechanisms.
• Fewer side effects in legs or buttocks compared to SNM – Because PNM does not involve broader stimulation of the sacral plexus, patients report less discomfort or involuntary stimulation in non-target areas such as the gluteal or lower limb regions.
• Targeted therapy for pudendal neuralgia and perineal pain – PNM is uniquely suited to treat specific pelvic neuropathies that are often resistant to conventional pain therapies or SNM.
Limitations:
• Not yet FDA-approved – Currently considered an off-label treatment, although clinical experience and interest in PNM are increasing worldwide.
• Complex anatomical access – The pudendal nerve follows a deep and variable anatomical pathway, often requiring image-guided or laparoscopic approaches for accurate electrode placement, which makes the procedure technically more demanding than SNM or PTNS.
• Very high risk of migration, since the electrode is not fixed to any anatomical structure in a region where the patient sits day after day.
2.4. The LION Procedure (Laparoscopic Implantation of Neuroprosthesis)
The LION Procedure (Laparoscopic Implantation of Neuroprosthesis) is an innovative neuromodulation technique developed by Prof. Marc Possover, which allows direct laparoscopic access to the pelvic nerves, particularly the sacral plexus and pudendal nerve. Unlike conventional methods, the LION procedure enables the precise placement of electrodes under direct visual control, offering a more refined and targeted form of neurostimulation.
Indications:
• Neurogenic bladder – Especially in patients with spinal cord injuries, multiple sclerosis, or other neurologic
pathologies where bladder function is impaired.
• Failed SNM cases – A valuable option when standard sacral neuromodulation has been ineffective or poorly tolerated.
• Chronic pelvic pain syndromes – Including pudendal neuralgia, sacral radiculopathy, and other forms of neuropathic pelvic pain that are refractory to conventional therapies.
• Fowler’s Syndrome – A rare condition characterized by urinary retention in young women due to urethral sphincter overactivity; the LION procedure offers a novel treatment avenue by targeting the responsible nerve pathways.
Strengths:
• Direct nerve visualization and stimulation – Laparoscopy provides precise anatomical access, allowing for targeted electrode placement on specific nerve branches (e.g., pudendal nerve, sciatic nerve, lumbosacral plexus). This enhances therapeutic precision and potentially improves outcomes.
• Avoids complications of transforaminal SNM – The approach bypasses the sacral foramina, reducing the risk of lead migration, gluteal pain, and undesired stimulation in the lower limbs, which are frequent issues in conventional SNM.
Limitations:
• Requires laparoscopic surgical expertise – The technique is technically demanding and must be performed by surgeons skilled in pelvic laparoscopy and neuropelveology.
• Not yet standard practice in most centers – Although the LION procedure has shown promising results, it remains a specialized technique, primarily performed in highly specialized centers, and is not yet part of routine clinical algorithms or international guidelines.
2.5. Genital Nerve Stimulation (GNS): A New Paradigm
The GNS procedure (Genital Nerve Stimulation) introduces a minimally invasive, retropubic surgical technique that enables the direct placement of electrodes on the dorsal genital nerves—branches of the pudendal nerve responsible for sensory and autonomic control of the external genitalia and lower urinary tract. Unlike SNM or PNM, GNS avoids involvement of the sacral spinal roots or foramina, offering a straightforward and anatomically targeted approach to neuromodulation.
Indications:
• Overactive bladder (OAB) – Effective for reducing urgency, frequency, and urge incontinence.
• Urinary and fecal incontinence – Particularly in patients with sphincter dysfunction or refractory symptoms.
• Sexual dysfunction – Especially in cases of genital sensory deficits or impaired sexual arousal.
• Systemic disorders – Preliminary data suggest potential systemic neuromodulatory effects, with beneficial influence on osteoporosis, depression, or fatigue syndromes, through autonomic pathways.
Strengths:
• Inspired by the TVT technique – familiar to gynecologic surgeons – The retropubic trajectory is analogous to the transvaginal tape (TVT) placement, making the learning curve manageable for clinicians experienced in urogynecologic surgery.
• No need for cystoscopy, trial stimulation, or sacral access – Simplifies the procedure significantly compared to SNM, making it more accessible and less invasive for both patients and physicians.
• Fully hidden implant with minimal lifestyle restrictions – The entire system remains subcutaneously concealed,
and no visible components or external connectors are needed, preserving body image and lifestyle comfort.
• High reproducibility and safety profile – The procedure has shown consistent outcomes with low complication
rates, and its anatomically guided approach minimizes surgical risk.
Limitations:
• Requires further clinical validation and regulatory approval – While initial results are promising, larger multi center trials and long-term outcome studies are still needed to establish broad clinical acceptance and formal approval by regulatory bodies.
• Currently limited to specialized centers – The GNS technique is not yet widely available and remains restricted to expert centers with experience in pelvic neuromodulation and minimally invasive gynecologic surgery.
2.6. Clinical Comparison and Future Directions
3. Anatomical Differences Between GNS, SNM, and PTNS – A Comparative Overview
A key anatomical distinction between Genital Nerve Stimulation (GNS) – targeting the dorsal nerve of the penis/clitoris, the cavernous nerve, and the autonomic genital nerves – and more conventional neuromodulation approaches such as Sacral Neuromodulation (SNM) and Posterior Tibial Nerve Stimulation (PTNS) lies inthe location, type, and function of the nerves being stimulated, as well as the directness of neuromodulatory influence.
Anatomical Target Sites
Nerve Fiber Types Affected
Summary
Compared to SNM and PTNS, GNS offers a more anatomically precise and differentiated neuromodulatory approach, especially suited for:
- Targeting genital pain syndromes
- Addressing sexual dysfunctions
- Directly influencing the autonomic pelvic nervous system, including the pelvic and hypogastric plexus
SNM and PTNS, on the other hand, are less specific but effective for central modulation, particularly in bladder storage/voiding dysfunctions. However, due to their indirect mechanism of action, they may have limited effect in cases of neuropelveological pain syndromes or genital autonomic dysfunctions.
4. Complications and Complication Rates – Comparative Overview
5. Cost Comparison Overview of Pelvic Neuromodulation Techniques
6. Conclusion
While SNM and PTNS are effective, they are limited by technical complexity, invasiveness, or insufficient efficacy. The GNS procedure presents a transformative opportunity to bridge the gap between neuro-urology and
gynecology by offering an easy, minimally invasive, gynecologist-performable neuromodulation technique. Further clinical research and integration into gynecologic training could make GNS a standard treatment modality for pelvic disorders.
GNS provides a highly targeted, low-risk, and cost-efficient solution particularly suited for gynecologic and neuropelveologic conditions. In contrast, SNM and PTNS offer broader but less differentiated approaches with higher procedural and maintenance burdens. Emerging techniques such as the LION Procedure and PNM offer additional tools, particularly in complex or refractory cases, albeit with higher technical requirements. A strategic integration of these modalities depending on indication, anatomical considerations, and patient profile can optimize outcomes in pelvic neuromodulation.
