Sacral neuromodulation for the treatment of overactive bladder: systematic review and future prospects

A Deep Analysis of the Pelvic Floor Motor Response in Sacral Neuromodulation Linking It to Outcome

OBJECTIVES

This study aimed to characterize the pelvic floor muscles (PFM) motor response provoked during sacral neuromodulation (SNM) programming, determining its utility in improving therapy delivery.

MATERIALS AND METHODS

This prospective study (January 2018-September 2021) included patients with overactive bladder (OAB) or nonobstructive urinary retention (NOUR) who underwent unilateral SNM. An external pulse generator was connected for three weeks. Success was defined as ≥50% improvement. Sensory threshold (ST), motor threshold (MT), and their ratio (MT-ST) were analyzed. PFM electromyography was recorded using a multiple array probe. A linear regression model with ST, MT, MT-ST, and mean natural log transformation (peak-to peak-amplitude) vs outcome (percentage improvement) was performed. Differences in electrical PFM motor response amplitude between different electrical stimulation levels (ST ± 0.5 mA) and different parts (four sides, three depths) of the pelvic floor were modeled using linear mixed model analysis (LMM).

RESULTS

The study population comprised 64 women (overall success 80%). Responders presented with significantly lower MT and MT-ST (unpaired t-test: p = 0.0271 and p = 0.0158, respectively). MT and MT-ST proved a significant relationship with percentage improvement (linear regression [lin. Regr.] p = 0.0304, R2 = 0.0745 and lin. Regr. p = 0.0107, R2 = 0.1020, respectively). PFM amplitude showed a significant relationship with percentage improvement for all stimulation amplitudes (ST ± 0.5 mA) (lin. Regr. p < 0.0001, R2 = 0.2560), and subsensory stimulation intensities (lin. Regr. p = 0.0008, R2 = 0.1673). Responders presented with a different evolution in increase in overall peak-to-peak amplitude over increased stimulation intensities (LMM: p = 0.0160), presenting with a significantly higher slope. This was significantly different depending on the percentage improvement for all the different sides and depths, with contralateral superior being the only exception (LMM: p = 0.0071, range: 0.0663-<0.0001).

CONCLUSIONS

A clear correlation was found between therapy efficacy and PFM motor response elicited by unilateral sacral spinal nerve stimulation, linking lead placement and SNM outcome. Responders presented with lower MTs, lower MT-STs, higher compound muscle action potentials, and higher continuous activation of their PFM at subsensory stimulation levels than did nonresponders.

A pain in the pocket: Prevalence of pocket pain in patients with implantation of neuromodulation systems: A retrospective study

INTRODUCTION

Implantable pulse generator (IPG) is a neurostimulation therapy mediated by electrodes and surgically implanted in a subcutaneous "pocket" used for the control of numerous pathologies. This study examines both the prevalence of pain associated with IPG implantation ("pain pocket syndrome") and its associated characteristics.

MATERIALS AND METHODS

56 patients with an IPG were included in the study. A health questionnaire was conducted to determine the presence of pain associated with the pocket and its neuropathic characteristics, as well as associated aesthetic concerns, location, situations that accentuate or alleviate pain, medications used for baseline and pocket pain control and other factors associated.

RESULTS

Pain in the area of implantation of the IPG had a prevalence of 52.6% of patients (n = 27), in our sample, with a mean score on the visual analogic scale (VAS) of 4.9 points [3.9-5.8 points], with neuropathic characteristics in 53.3% (n = 16) of the patients with pain, with differences between the mean VAS score of the female (5.5 [4.3-5.8 points]) and males (3.5 points [2.1-4.9 points]) (p = 0.04).

CONCLUSION

Pocket pain is a condition with a higher prevalence than described in previous studies, being of a higher intensity in females, involving a moderate pain in the area of implantation of the neuromodulating therapy. This pain has neuropathic characteristics and could require a repositioning intervention. Hence, more studies in this field should be carried to detect and prevent this syndrome.

An update on the cognitive safety of antimuscarinics in the treatment of overactive bladder

INTRODUCTION

Antimuscarinics are often the first-choice medications used to treat overactive bladder (OAB), a condition that increasingly affects the aging population. However, concerns regarding their potential impact on cognitive function have persisted for more than a decade.

AREAS COVERED

This review was conducted to update the literature on the cognitive safety profiles of various antimuscarinics, integrating findings from both recent and earlier studies to present an updated and comprehensive analysis. A search of English-language publications, including electronic databases and gray literature, focused on the cognitive impacts of antimuscarinics, resulting in a review and assessment of diverse studies and their associated outcomes.

EXPERT OPINION

Oxybutynin requires caution due to potential adverse effects, suggesting a need to consider alternative therapies. Darifenacin, while promising in preserving cognitive function, warrants further investigation for use in dementia patients. Fesoterodine has shown tolerance without cognitive decline in controlled trials. However, Tolterodine and Solifenacin present conflicting evidence regarding cognitive impairment and dementia risk, respectively, necessitating additional research to ascertain their safety profiles. Careful monitoring and treatment of patients taking these medications for cognitive impairment are essential. Further research, particularly in vulnerable populations, is crucial to establish cognitive safety profiles of various antimuscarinics and inform optimal OAB treatment strategies.

Burst Stimulation Evokes Increased Bladder and Urethral Pressure in Patients With Sacral Neuromodulation, Indicating Potential Activation of the Autonomic Nervous System: A Pilot Study

OBJECTIVES

Currently, sacral neuromodulation (SNM) outcomes are often suboptimal, and changing stimulation parameters might improve SNM efficacy. Burst stimulation mimics physiological burst firing of the nervous system and might therefore benefit patients treated with SNM. The purpose of the present pilot study was to evaluate the effect of various Burst SNM paradigms on bladder and urethral pressure in patients with overactive bladder (OAB) or nonobstructive urinary retention (NOUR).

MATERIALS AND METHODS

The bladder was filled to 50% of its capacity under general anesthesia in six patients with an implanted sacral lead for SNM purposes. Bladder pressure, and mid- and proximal urethral pressure were measured using conventional (Con-) SNM and various Burst SNM paradigms (10-20-40 Hz interburst frequency) with increasing amplitudes up to 5 mA for Con-SNM and 4 mA for Burst SNM.

RESULTS

Burst SNM caused a substantial increase in both bladder and urethral pressure. In contrast, Con-SNM caused a milder increase in urethral pressure, and only one patient showed a modest increase in bladder pressure. Furthermore, the pressure increase was higher in the proximal urethra than in the midurethra using Burst-SNM, whereas Con-SNM caused comparable increases in proximal and midurethra pressure.

CONCLUSIONS

Burst SNM induces bladder contraction compared with Con-SNM and induces higher pressure increases in bladder and proximal urethra than does Con-SNM in patients with OAB or NOUR, indicating a higher degree of autonomic nervous system stimulation. The observed responses could not be fully explained by the total charge of the Burst SNM paradigms, which suggests the importance of individual Burst SNM parameters, such as frequency and amplitude. Future studies should assess the feasibility and efficacy of Burst SNM in awake patients.

Transcutaneous neuromodulation versus oxybutynin for neurogenic detrusor overactivity in persons with spinal cord injury: A randomized, investigator blinded, parallel group, non-inferiority controlled trial

STUDY DESIGN

This study is a randomized, investigator-blinded, controlled trial with a non-inferiority design.

OBJECTIVE

To investigate the effectiveness of neuromodulation by transcutaneous electrical stimulation of the somatic afferent nerves of the foot in neurogenic detrusor overactivity (NDO) in persons with spinal cord injury (SCI) and compare its effectiveness with oral oxybutynin.

SETTING

The study was conducted in a rehabilitation in-patient ward of a tertiary care hospital.

METHODS

Twenty-nine persons with SCI with NDO, either sex, aged 18 years and above were randomized into two groups, one group receiving oral oxybutynin (5 mg thrice a day for two weeks) and the other transcutaneous electrical stimulation (5 Hz, 200 µs pulse, biphasic, amplitude up to 60 mA, 30 min/day for two weeks). Bladder capacity was evaluated by clinical bladder evaluation (i.e. bladder capacity measured by adding leak volume, voiding volume if any, and post-void residue using a catheter) and cystometric bladder capacity by one-channel cystometry. Maximum cystometric pressure was evaluated by one-channel water cystometry. Data were analyzed with Fisher's Exact, t-test, and Wilcoxon rank sum tests.

RESULTS

Bladder capacity improved significantly in the oxybutynin and neuromodulation groups as measured by one-channel water cystometry (136 ml vs. 120.57 ml) and clinical evaluation (138.93 ml vs. 112 ml). The increase in the neuromodulation group achieved the pre-decided non-inferiority margin of 30 ml over the oxybutynin group when measured by one-channel water cystometry but not by clinical evaluation. Maximum cystometric pressure did not significantly improve in either group when compared with the baseline.

CONCLUSION

Transcutaneous neuromodulation and oxybutynin effectively increased bladder capacity in persons with SCI with NDO. Neuromodulation by once-a-day transcutaneous electrical stimulation was non-inferior to thrice-a-day oxybutynin when evaluated by one-channel water cystometry.Trial registration: Clinical Trials Registry India identifier: CTRI/2018/05/013735.

Outcomes of sequential third-line therapies in patients with refractory overactive bladder

INTRODUCTION

Sacral neuromodulation (SNM) and onabotulinumtoxinA (BoNTA) injection are third-line therapies for overactive bladder (OAB). Although the efficacy of each third-line treatment has been well established in clinical trials, there is far less information about performing one third-line therapy after the other. Our aim is thus to investigate the outcomes of post-SNM BoNTA and post-BoNTA SNM as "second" third-line treatments.

METHODS

We retrospectively reviewed all OAB patients who had both SNM and BoNTA between 2013 and 2022. The primary endpoint was the response rates (>50% improvements) of the second third-line treatments. Secondary endpoints were the proportion of the patients who achieved total dry, the duration of treatments of patients who had significant responses, and risk factors that are associated with treatment response or duration of treatments.

RESULTS

A total of 172 patients had two third-line therapies. There were 104 patients who had post-SNM BoNTA and 68 patients who had post-BoNTA SNM. In the post-SNM BoNTA group, 62.5% (65/104) had significant responses after BoNTA treatment. In the post-BoNTA SNM group, 61.8% (44/68) had significant responses after SNM treatment. The proportions of patients who became dry were 21.2% and 23.5%, respectively. In the post-SNM BoNTA group, spinal pathology is associated with a lower probability of a significant response (48.9% vs. 73.7%, p-value = 0.0105).

CONCLUSIONS

BoNTA or SNM remains a viable option for refractory OAB after patients fail from one another. Spinal pathology is associated with a poorer response of post-SNM BoNTA.

A biodegradable and flexible neural interface for transdermal optoelectronic modulation and regeneration of peripheral nerves

Optoelectronic neural interfaces can leverage the photovoltaic effect to convert light into electrical current, inducing charge redistribution and enabling nerve stimulation. This method offers a non-genetic and remote approach for neuromodulation. Developing biodegradable and efficient optoelectronic neural interfaces is important for achieving transdermal stimulation while minimizing infection risks associated with device retrieval, thereby maximizing therapeutic outcomes. We propose a biodegradable, flexible, and miniaturized silicon-based neural interface capable of transdermal optoelectronic stimulation for neural modulation and nerve regeneration. Enhancing the device interface with thin-film molybdenum significantly improves the efficacy of neural stimulation. Our study demonstrates successful activation of the sciatic nerve in rodents and the facial nerve in rabbits. Moreover, transdermal optoelectronic stimulation accelerates the functional recovery of injured facial nerves.

Preliminary analysis of stimulation parameters for sacral neuromodulation in different indications: a multicenter 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, the authors 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 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 internal pulse generator 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 nonobstructive 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.

Retrospective Observational Study of Treatment Patterns and Efficacy of onabotulinumtoxinA Therapy in Patients with Refractory Overactive Bladder in Clinical Practice

This study aimed to evaluate the treatment patterns and long-term efficacy of onabotulinumtoxinA injections in a clinical setting. This single-center retrospective study was conducted on patients with refractory overactive bladder (OAB) aged 18 years or older who received onabotulinumtoxinA 100 IU administered between April 2012 and May 2022. The primary endpoint was the treatment pattern, including the retreatment rate and OAB medication prescription pattern. The duration and effectiveness of onabotulinumtoxinA treatment were analyzed using the overactive bladder symptom score and voiding diaries. A total of 216 patients were enrolled in this study, and the overall patient satisfaction rate was 55.1%. After the first injection, 19.9% received a second treatment, and 6.1% received three or more injections. The median duration until the second injection was 10.7 months. Among the patients, 51.4% resumed OAB medications after 2.96 months. The presence of urodynamic detrusor overactivity was observed only in female patients (odds ratio, 23.65; 95% CI, 1.84 to 304.40), which was associated with a good response. In contrast to clinical trials, the degree of improvement and retreatment rate did not meet expectations. Our findings provide valuable insights into the effectiveness of onabotulinumtoxinA injections in patients with refractory OAB symptoms in real-world practice.

Effectiveness and safety of sacral neuromodulation for neurogenic bladder

BACKGROUND

The treatment of neurogenic bladder (NB) is a challenge because conventional therapy often fails. Sacral neuromodulation (SNM) is a minimally invasive technique and an unconventional treatment for neurogenic bladder. Its research is still in the exploratory stage. The research on its effectiveness and safety is not clear.

OBJECTIVE

To assess the effectiveness and safety of sacral neuromodulation (SNM) for neurogenic bladder (NB).

METHODS

By searching the PubMed databases and Cochrane Library databases, combined with the method of literature tracing, the clinical researches and works on neurogenic bladder and sacral neuromodulation therapy were collected. Two reviewers independently selected and extracted data, (1) determine whether the study meets the inclusion criteria and exclude the literature that meets the exclusion criteria. (2) Researchers' screening results and data, if there are differences in the results, will be discussed to eliminate the differences. (3) Read the full text of the literature carefully to determine the final literature to be included. (4) The relevant data of 11 independent studies, a total of 291 patients, were systematically reviewed using review manager 5.3 software.

RESULTS

This research included 11 independent studies with a total of 291 patients. The improvements of main outcomes before and after SNM therapy were significant: incontinence episodes /24 h (WMD -2.52; 95%CI-3.14-1.90; p <0.001), frequency/24 h (WMD-5.96; 95%CI -6.27，-5.66; p <0.001), voiding volume (WMD 116.09 mL; 95%CI 86.68，145.51; p <0.001), cystometric capacity (WMD 129.84 mL; 95%CI 100.53, 159.15; p <0.001), post-void residual volume (WMD-198.00 mL; 95%CI-264.60, -131.40; p <0.001), clean intermittent self-catheterization/24 h (WMD-2.48; 95%CI -2.96, -2.00; p <0.001).

CONCLUSION

This systematic review indicated that the sacral neuromodulation treatment for neurogenic bladder was effective and safe.

Comparison of different types of therapy for overactive bladder: A systematic review and network meta-analysis

To compare the efficacy and safety of different interventions [including antimuscarinics, mirabegron, OnabotulinumtoxinA, sacral neuromodulation (SNM) and peripheral tibial nerve stimulation (PTNS)] for treating idiopathic overactive bladder (OAB). PubMed, Embase, Cochrane Library, and other sources were searched for randomized controlled trials (RCTs) comparing interventions for overactive bladder from 1 January 2000 to 19 April 2021. A systematic review and network meta-analysis were performed by two authors independently. Fifty-five RCTs involving 32,507 patients were included in this analysis. Overall, antimuscarinics, mirabegron, OnabotulinumtoxinA, sacral neuromodulation, and peripheral tibial nerve stimulation were more efficacious than placebo, and sacral neuromodulation showed the best effect for reducing micturition frequency, urgency episodes and urgency urinary incontinence episodes. OnabotulinumtoxinA was the best intervention for achieving reductions of 100 and ≥50% in the number of urinary incontinence episodes/day, and peripheral tibial nerve stimulation was the best intervention for reducing urinary incontinence episodes. Antimuscarinics, mirabegron and peripheral tibial nerve stimulation had a similar efficacy for reducing micturition frequency, urinary incontinence episodes and urgency urinary incontinence episodes. The results revealed that all interventions examined herein were efficacious for managing adult overactive bladder syndrome compared with placebo. Furthermore, sacral neuromodulation and OnabotulinumtoxinA were the most efficient treatments for overactive bladder.

Systematic review registration

[https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=251966], identifier [CRD42021251966].