Sacral Neuromodulation for Lower Urinary Tract and Bowel Dysfunction in Animal Models: A Systematic Review With Focus on Stimulation Parameter Selection

Preliminary analysis of stimulation parameters for sacral neuromodulation in different indications: A multi-center retrospective cohort study from China

BACKGROUND

Sacral neuromodulation (SNM) is an effective approach for treating lower urinary tract dysfunction (LUTD), and stimulation programming is essential for successful treatment. However, research on SNM programming for various indications is limited. Thus, we aimed to determine whether there were differences in the stimulation parameters for different SNM indications and the appropriate programming recommendations.

MATERIALS AND METHODS

Clinical data were retrospectively collected from patients with LUTD who underwent SNM and completed internal pulse generator (IPG) implantation. The parameters with the highest patient satisfaction or the most symptom improvement during the test period were considered optimal and used to set the programming after IPG implantation.

RESULTS

After screening, 282 patients were enrolled and categorized into four groups based on the following indications: refractory overactive bladder (OAB) (n=61), neurogenic lower urinary tract dysfunction (nLUTD) (n=162), interstitial cystitis/painful bladder syndrome (IC/BPS) (n=24), and idiopathic non-obstructive urinary retention (NOUR) (n=35). When analyzing the optimal stimulus parameters, disparities in the stimulation amplitude and pulse frequency were noted among the four groups. The stimulation amplitude in the nLUTD group was higher than that in the idiopathic NOUR group (P=0.013). Differences in pulse frequency were observed between the refractory OAB and nLUTD groups (P<0.001) and between the refractory OAB and idiopathic NOUR groups (P=0.001). No differences in the electrode configuration or pulse width settings existed among the four groups.

CONCLUSIONS

The stimulation parameters for SNM varied among the different indications. For the initial programming of stage I, most patients are recommended to start with stimulation amplitudes below 2 V, although patients with nLUTD may benefit from higher amplitudes. A standard pulse width of 210 μs is recommended for all patients. However, for individuals experiencing nLUTD or idiopathic NOUR, the pulse frequency can begin above the standard 14 Hz but not exceed 50 Hz.

Bioelectronic Medicine: a multidisciplinary roadmap from biophysics to precision therapies

Bioelectronic Medicine stands as an emerging field that rapidly evolves and offers distinctive clinical benefits, alongside unique challenges. It consists of the modulation of the nervous system by precise delivery of electrical current for the treatment of clinical conditions, such as post-stroke movement recovery or drug-resistant disorders. The unquestionable clinical impact of Bioelectronic Medicine is underscored by the successful translation to humans in the last decades, and the long list of preclinical studies. Given the emergency of accelerating the progress in new neuromodulation treatments (i.e., drug-resistant hypertension, autoimmune and degenerative diseases), collaboration between multiple fields is imperative. This work intends to foster multidisciplinary work and bring together different fields to provide the fundamental basis underlying Bioelectronic Medicine. In this review we will go from the biophysics of the cell membrane, which we consider the inner core of neuromodulation, to patient care. We will discuss the recently discovered mechanism of neurotransmission switching and how it will impact neuromodulation design, and we will provide an update on neuronal and glial basis in health and disease. The advances in biomedical technology have facilitated the collection of large amounts of data, thereby introducing new challenges in data analysis. We will discuss the current approaches and challenges in high throughput data analysis, encompassing big data, networks, artificial intelligence, and internet of things. Emphasis will be placed on understanding the electrochemical properties of neural interfaces, along with the integration of biocompatible and reliable materials and compliance with biomedical regulations for translational applications. Preclinical validation is foundational to the translational process, and we will discuss the critical aspects of such animal studies. Finally, we will focus on the patient point-of-care and challenges in neuromodulation as the ultimate goal of bioelectronic medicine. This review is a call to scientists from different fields to work together with a common endeavor: accelerate the decoding and modulation of the nervous system in a new era of therapeutic possibilities.

Sacral Nerve Stimulation Alleviates Intestinal Inflammation Through Regulating the Autophagy of Macrophages and Activating the Inflammasome Mediated by a Cholinergic Antiinflammatory Pathway in Colitis Rats

BACKGROUND

Inflammatory bowel disease (IBD) is characterized by chronic progressive intestinal inflammation. Sacral nerve stimulation (SNS) ameliorates colon inflammation caused by IBD. The aim of this study was to investigate the antiinflammatory benefits of SNS in colitis rats and explore the roles of the cholinergic antiinflammatory pathway, macrophage autophagy, and nucleotide oligomerization domain-like receptor thermal protein domain associated protein 3 (NLRP3) inflammatory bodies.

MATERIALS AND METHODS

Rats were divided into four groups: healthy control, dextran sulfate sodium (DSS), DSS + sham-SNS, and DSS + SNS groups. An electrode was surgically placed in the right sacral nerve (S3) for stimulation. The disease activity index (DAI) score was recorded each day, and the degree of inflammatory injury was evaluated using hematoxylin and eosin staining. The alpha7 nicotinic acetylcholine receptor (α7nAChR) and autophagy- and NLRP3-related factors were assessed using immunofluorescence staining and Western blotting.

RESULTS

The DSS group showed a higher DAI score, colon shortening, upregulated proinflammatory action, and colon damage, and the DSS + SNS group showed significantly improved symptoms. The number of α7nAChR+ cells and the expression level of autophagy decreased in the DSS group but increased in the DSS + SNS group. Conversely, the DSS group showed increased activation of NLRP3 inflammatory bodies, whereas the DSS + SNS group showed decreased activation of NLRP3 inflammatory bodies.

CONCLUSION

In this study, SNS ameliorated colon inflammation by enhancing macrophage autophagy and inhibiting the activation of NLRP3 inflammatory bodies, which may be related to the opening of the cholinergic antiinflammatory pathway.

Efficacy and Safety of Sacral Neuromodulation by Converting Constant Frequency Stimulation Into Variable Frequency Stimulation in Patients With Detrusor Overactivity and Impaired Contractility: A Single-Center Prospective Study

OBJECTIVES

In patients with detrusor overactivity with impaired contractility (DOIC), it is difficult to relieve abnormal lower urinary tract symptoms during both storage and voiding using sacral neuromodulation (SNM) with constant frequency stimulation (CFS). We sought to evaluate the efficacy and safety of SNM using variable frequency stimulation (VFS) in patients with DOIC by comparing it with outcomes of SNM with CFS.

MATERIALS AND METHODS

Between September 2020 and May 2021, we prospectively enrolled 20 patients with DOIC, confirmed on urodynamic examination, and administered SNM with VFS. The patients were followed up and required to maintain voiding diaries and record scale scores of overactive bladder symptoms, psychology and quality of life, uroflowmetry, ultrasonic postvoid residual urine, and adverse events at baseline and during the CFS and VFS phases.

RESULTS

The average testing phase was 26.3 ± 4.1 days. Compared with baseline values, overactive bladder symptom, psychologic health questionnaire, and quality of life scores, in addition to voiding frequency, urgency incontinence frequency, daily catheterization volume of voiding diary, and ultrasonic postvoid residual (PVR) decreased significantly during both the CFS and VFS phases (p < 0.05). The average voided volume, functional bladder capacity, and maximum urine flow rate significantly increased during the CFS and VFS phases (p < 0.05). In the VFS phase, voiding frequency, urgency incontinence frequency, daily catheterization volume of voiding diary, and ultrasonic PVR further decreased (p < 0.05), whereas functional bladder capacity, maximum urine flow rate, quality of life score, overactive bladder symptom score, and psychologic health questionnaire score further improved compared with results obtained in the CFS phase (p < 0.05). In the VFS phase, the success rate of further improvement of symptoms was 85.0%, and no new complications were noted.

CONCLUSIONS

SNM that converts CFS into VFS may be an effective treatment option for patients with DOIC, exhibiting no increase in adverse events.

Transcutaneous Electrical Stimulation of the Abdomen, Ear, and Tibial Nerve Modulates Bladder Contraction in a Rat Detrusor Overactivity Model: A Pilot Study

PURPOSE

The global prevalence of overactive bladder (OAB) is estimated at 11.8%. Despite existing treatment options such as sacral neuromodulation, a substantial number of patients remain untreated. One potential alternative is noninvasive transcutaneous electrical stimulation. This form of stimulation does not necessitate the implantation of an electrode, thereby eliminating the need for highly skilled surgeons, expensive implantable devices, or regular hospital visits. We hypothesized that alternative neural pathways can impact bladder contraction.

METHODS

In this pilot study, we conducted transcutaneous electrical stimulation of the abdominal wall (T6-L1), the ear (vagus nerve), and the ankle (tibial nerve) of 3 anesthetized female Sprague-Dawley rats. Stimulation was administered within a range of 20 Hz to 20 kHz, and its impact on intravesical pressure was measured. We focused on 3 primary outcomes related to intravesical pressure: (1) the pressure change from the onset of a contraction to its peak, (2) the average duration of contraction, and (3) the number of contractions within a specified timeframe. These measurements were taken while the bladder was filled with either saline or acetic acid (serving as a model for OAB).

RESULTS

Transcutaneous stimulation of the abdominal wall, ear, and ankle at a frequency of 20 Hz decreased the number of bladder contractions during infusion with acetic acid. As revealed by a comparison of various stimulation frequencies of the tibial nerve during bladder infusion with acetic acid, the duration of contraction was significantly shorter during stimulation at 1 kHz and 3 kHz relative to stimulation at 20 Hz (P = 0.025 and P = 0.044, respectively).

CONCLUSION

The application of transcutaneous electrical stimulation to the abdominal wall, ear, and tibial nerve could provide less invasive and more cost-effective treatment options for OAB relative to percutaneous tibial nerve stimulation and sacral neuromodulation. A follow-up study involving a larger sample size is recommended.

Sacral neuromodulation remote programming in patients with refractory lower urinary tract dysfunction: China’s experience during the COVID-19 pandemic

Objectives

Sacral neuromodulation is an effective, minimally invasive treatment for refractory lower urinary tract dysfunction. However, regular postoperative programming is crucial for the maintenance of the curative effects of electronic sacral stimulator devices. The outbreak of coronavirus disease 2019 (COVID-19) limited the ability of practitioners to perform traditional face-to-face programming of these stimulators. Therefore, this study aimed to evaluate the application of remote programming technology for sacral neuromodulation during the COVID-19 pandemic in China.

Materials and methods

We retrospectively collected data including baseline and programming information of all patients with lower urinary tract dysfunction who underwent sacral neuromodulation remote programming in China after the outbreak of COVID-19 (i.e., December 2019). The patients also completed a self-designed telephone questionnaire on the subject.

Results

A total of 51 patients from 16 centers were included. They underwent 180 total remote programming visits, and 118, 2, 25, and 54 voltage, current, pulse width, and frequency adjustments, respectively, were performed. Additionally, remote switching on and off was performed 8 times; impedance test, 54 times; and stimulation contact replacement, 25 times. The demand for remote programming was the highest during the first 6 months of sacral neuromodulation (average, 2.39 times per person). In total, 36 out of the 51 patients completed the questionnaire survey. Of these, all indicated that they chose remote programming to minimize unnecessary travel because they had been affected by COVID-19. The questionnaire also showed that remote programming could reduce the number of patient visits to the hospital, save time, reduce financial costs, and would be easy for patients to master. All surveyed patients indicated that they were satisfied with remote programming and were willing to recommend it to other patients.

Conclusion

Remote programming for sacral neuromodulation is feasible, effective, safe, and highly recommended by patients with refractory lower urinary tract dysfunction. Remote programming technology has great development and application potential in the post-pandemic era.

The role of percutaneous tibial nerve stimulation (PTNS) in the treatment of chronic anal fissure: a systematic review

PURPOSE

This study was designed to summarize the current evidence regarding the role of percutaneous tibial nerve stimulation (PTNS) in the treatment of chronic anal fissure (CAF).

METHODS

The present systematic review of the literature was conducted on the basis of the PRISMA guidelines and the Cochrane Handbook for Systematic Reviews of Interventions. The primary endpoint of our study was the CAF recurrence rate. Quality assessment was based on the RoB 2 tool and the Case Series Quality Checklist.

RESULTS

Overall, 5 studies and 102 patients were included. A considerably heterogeneity in the neuromodulation technique and setting was identified. The pooled recurrence rate was estimated at the level of 19% (16/84). Post-interventional pain and Wexner scores were considerably reduced. The 2-month healing rate was 72% (18/25), whereas 73.6% of patients were symptom-free at 6 months.

CONCLUSIONS

PTNS is an effective alternative for the non-operative management of CAF. Due to several limitations further larger and higher quality studies are required.

Stimulation Parameters for Sacral Neuromodulation on Lower Urinary Tract and Bowel Dysfunction-Related Clinical Outcome: A Systematic Review

Objective

Sacral neuromodulation (SNM) has been used to treat patients with lower urinary tract dysfunction and bowel dysfunction for many years. Success rates vary between 50% and 80%, indicating that there is much room for improvement. Altering stimulation parameters may result in improved outcome. This paper reports a systematic review of the clinical efficacy of nonconventional stimulation parameters on urinary tract and bowel dysfunction.

Materials and Methods

Three databases were used for the literature search: Ovid (Medline, Embase) and PubMed. Papers were screened by two independent reviewers, who also extracted data from these papers. Clinical papers studying SNM stimulation parameters, that is, intermittent stimulation, frequency, pulse width, and amplitude, in urinary tract and bowel dysfunction were included. Quality of included papers was assessed using standardized guidelines.

Results

Out of 5659 screened papers, 17 papers, studying various stimulation parameters, were included. Overall quality of these papers differed greatly, as some showed no risk of bias, whereas others showed high risk of bias.

Stimulation parameters included intermittent stimulation, frequency, pulse width, amplitude, and unilateral vs. bilateral stimulation. Especially high frequency SNM and either a narrow or wide pulse width seem to improve efficacy in patients with bowel dysfunction. Additionally, implementation of short cycling intervals is promising to improve quality of life for patients with urinary tract or bowel dysfunction.

Conclusion

The results of our systematic review indicate that stimulation parameters may improve efficacy of SNM in treatment of both urinary tract dysfunction and bowel dysfunction.