The Effect of Sacral Nerve Modulation on Cerebral Evoked Potential Latency in Fecal Incontinence and Constipation

Methodologies to elicit and record pudendal somatosensory evoked potentials in adult humans: A systematic review

OBJECTIVE

The purpose of this systematic review was to characterize methodologies reported in the literature to elicit and record pudendal somatosensory evoked potentials (SEPs) in human adults.

METHODS

We conducted an electronic literature search in MEDLINE, Embase, CENTRAL, and CINAHL for studies that elicited pudendal SEPs via electrical stimulation and recorded responses though electroencephalography. From included studies, we extracted methodological details of how the SEPs were evoked and recorded.

RESULTS

132 studies were included in our review. The majority of participants were male (n = 6742/8526, 79%). Almost all studies stimulated the dorsal nerve of penis/clitoris. Stimulus parameters varied, with most standardizing stimulus intensity to 2-4x perceptual threshold, pulse duration to 0.1-0.2 ms, and frequency to 3 Hz. The number of stimuli recorded varied by clinical population.

CONCLUSIONS

Our results demonstrate the inconsistencies of pudendal SEP methodology in the literature, with the majority (77%) of publications not reporting enough detail to reasonably replicate their protocol. Most research to date has been conducted in males, highlighting the paucity of female pelvic neurophysiology research.

SIGNIFICANCE

We propose a Pudendal SEP Reporting Checklist for adequate reporting of pudendal SEP protocols. Optimal sex- and patient-specific methodologies to investigate all branches of the pudendal nerve need to be established.

Effects of Posterior Tibial Nerve Stimulation on Fecal Incontinence: An Umbrella Review

PURPOSE

This study aimed to summarize relevant data from previous systematic reviews (SRs) and conduct comprehensive research on the clinical effects of posterior tibial nerve stimulation (PTNS), via the transcutaneous posterior tibial nerve stimulation (TPTNS) or percutaneous posterior tibial nerve stimulation (PPTNS) method on fecal incontinence (FI).

MATERIALS AND METHODS

In adherence to the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines, a systematic search was conducted on PubMed, Embase, Scopus, and Web of Science databases. We included English-language, full-text SRs reporting outcomes for FI following either PPTNS or TPTNS. The quality of included studies was assessed using the Joanna Briggs Institute checklist. In addition, reanalyzing the meta-analyses was conducted using Comprehensive Meta-Analysis (CMA) software version 3.0 to achieve effect sizes and the level of statistical significance was set at p ≤ 0.05.

RESULTS

From a total of 835 citations, 14 SRs met our inclusion criteria. Four of these also conducted a meta-analysis. Most SRs reported an overall improvement in different study parameters, including bowel habits and quality of life. However, there were major inconsistencies across the results. The most studied outcome was FI episodes, followed by incontinence score. The summary outcomes showed no statistically significant changes in comparing PTNS with sham or sacral nerve stimulation (SNS) for FI (p > 0.05). However, the results of subgroup analysis based on the type of intervention in the control group revealed that FI episodes were significantly fewer than in the PTNS arm, whereas PTNS led to fewer episodes of FI than did the sham. In terms of incontinence score, the results showed that PTNS compared with sham did not change the incontinence score; however, SNS improved the score significantly in one eligible study for reanalysis when compared with PTNS (p < 0.001).

CONCLUSIONS

The findings of the current umbrella review suggest that PTNS can potentially benefit patients with FI. However, this is concluded from studies with a limited population, disregarding the etiology of FI and with limited follow-up duration. Therefore, caution must be taken in contemplating the results.

Efficacy of Tibial Nerve Stimulation on Fecal Incontinence in Patients With Low Anterior Resection Syndrome Following Surgery for Colorectal Cancer

OBJECTIVE

To systematically review the available literature on the efficacy of tibial nerve stimulation on faecal incontinence and quality of life in adult patients with low anterior resection syndrome following surgery for colorectal cancer.

METHODS

A primary search of electronic databases was conducted adopting a combination of search terms related to the following areas of interest: "efficacy", "tibial nerve stimulation" and "low anterior resection syndrome". A secondary search of the grey literature was performed in addition to checking the reference list of included studies and review papers. The review was reported following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. A descriptive analysis was used to integrate the review findings.

RESULTS

Five distinct studies involving 116 patients met the inclusion criteria for the review. The included studies suggest that tibial nerve stimulation may have a positive effect on faecal incontinence and quality of life in some patients with low anterior resection syndrome and might be considered as an additional treatment option.

CONCLUSION

There were a limited number of studies and a great degree of heterogeneity of evidence due to differences in participants' baseline characteristics, dropout rates, and follow-up periods. Further research adopting validated, consistent, and complex outcome assessment methods is recommended to determine the efficacy of tibial nerve stimulation for treatment of patients with low anterior resection syndrome.

Design of a Randomized Controlled Trial of Percutaneous Posterior Tibial Nerve Stimulation for the Treatment of Refractory Fecal Incontinence in Women: The NeurOmodulaTion for Accidental Bowel Leakage Study

OBJECTIVES

High-level evidence for second-line noninvasive treatments for fecal incontinence in women is limited. We present the rationale for and design of the NeuromOdulaTion for Accidental Bowel Leakage trial, a randomized controlled trial of percutaneous tibial nerve stimulation (PTNS) and validated sham stimulation in women with refractory accidental bowel leakage.

METHODS

The rationale and goals for a 2-part study with a run-in phase, use of a generic pulse generator for PTNS and sham stimulation, masking, participant inclusion, primary and secondary outcome measures, and adverse event collection are described. A superiority design will be used to compare change from baseline in St. Mark's score after 12 weekly stimulation sessions between PTNS and sham. Responders to initial treatment (PTNS or sham) will be assigned to scheduled or "as needed" intervention for up to 1 year. Secondary outcome measures include incontinence episodes and other bowel events recorded in a 14-day electronic bowel diary, general and condition-specific quality of life instruments, adaptive behavior, global impression of improvement, symptom control, and sexual function.

RESULTS

Sample size calculations determined that 165 participants (110 PTNS and 55 sham) would provide 90% power to detect greater than or equal to 4-point difference between PTNS and sham in change from baseline in St. Mark's score at 12 weeks.

CONCLUSIONS

The methods for the NeuromOdulaTion for Accidental Bowel Leakage trial will provide high-level evidence of the effectiveness and optimal maintenance therapy schedule of a low-cost PTNS protocol in community-dwelling women seeking second-line intervention for refractory accidental bowel leakage.

Sacral Nerve Modulation Has No Effect on the Postprandial Response in Irritable Bowel Syndrome

Purpose

Irritable bowel syndrome is a common gastrointestinal disorder with a global prevalence of approximately 11%. Onset or worsening of symptoms following digestion is one of the characteristics of the condition. The present study aimed at evaluating the postprandial sensory and motor response before and after treatment with sacral nerve modulation.

Patients and Methods

Twenty-one irritable bowel syndrome patients, 12 diarrhea-predominant and 9 mixed, were eligible for a 6-week sacral nerve modulation test period. Patients were investigated with multimodal impedance planimetry including a standardized meal at baseline and at the end of 2 weeks of suprasensory stimulation embedded in the 6-week sacral nerve modulation period.

Results

There was no statistical significant difference in the sensory response to heat or cold before and after sacral nerve modulation, p>0.05. At baseline, wall tension increased after the meal (mean 124.79 [range 82.5 to 237.3] mmHg.mm before the meal, mean 207.76 [range, 143.5 to 429] mmHg.mm after the meal), p=0.048 indicating a postprandial response. During sacral nerve modulation, the postprandial increase in wall tension did not reach statistical significance (mean 86.79 [range 28.8 to 204.5] mmHg.mm before the meal, mean 159.71 [range 71.3 to 270.8] mmHg.mm after the meal), p=0.277. However, there was no statistically significant difference between the postprandial wall tension at baseline and during sacral nerve modulation, p=0.489. Likewise, we found no difference between pressure or stretch ratio at baseline and during sacral nerve modulation, p>0.05.

Conclusion

Sacral nerve modulation does not exert its positive treatments effects in diarrhea-predominant and mixed irritable bowel syndrome through a modulation of the postprandial response.

Sacral nerve modulation for irritable bowel syndrome: A randomized, double-blinded, placebo-controlled crossover study

BACKGROUND

Irritable bowel syndrome (IBS) is among the most common gastrointestinal disorders, and a substantial proportion of patients have an insufficient response to treatment. In a single-blinded study, sacral nerve modulation (SNM) significantly reduced symptoms of IBS. The aim of the present double-blinded, randomized, placebo-controlled study was to evaluate the effect of SNM for IBS.

METHODS

We included patients with diarrhea-predominant or mixed IBS and a minimum baseline IBS-specific symptom score of 40 points (Gastrointestinal Symptom Rating Scale-IBS version). Patients underwent a 6-week period of SNM. In the first 4 weeks, the patients were randomized 1:1 to have the neurostimulator set subsensory or OFF for 2 weeks and then the opposite for another 2 weeks. Patients and investigators were blinded to settings. In the remaining 2 weeks, the stimulation was set suprasensory. IBS-specific symptoms and quality of life were assessed with validated questionnaires and bowel diaries.

KEY RESULTS

Twenty-one patients were randomized and eligible for analysis. The IBS-specific symptom score was reduced with borderline significance during stimulation (subsensory-OFF median change -1 (-26, 9), OFF-subsensory median change 8 (-11, 36); P = 0.0572). Pain was significantly reduced during stimulation (subsensory-OFF median change -1.5 (-4, 1), OFF-subsensory median change 1 (-4, 3); P = 0.0188), along with the number of daily bowel movements (subsensory-OFF median change 0 (-1.8, 0.2), OFF-subsensory median change 0.2 (-0.5, 1.1); P = 0.0373). The median placebo effect was 14% (0, 55).

CONCLUSION AND INFERENCES

Sacral nerve modulation for IBS seems promising but should be considered experimental until larger multicenter studies have been performed.

Assessment of brain activity during voluntary anal sphincter contraction: Comparative study in women with and without fecal incontinence

BACKGROUND

Voluntary anal sphincter function is driven by an extended network of brain structures, most of which are still unknown. Disturbances in this function may cause fecal incontinence. The aim of this study was to characterize the cerebral areas involved in voluntary contraction of the anorectal sphincter in healthy women and in a group of patients with fecal incontinence by using a standardized functional magnetic resonance imaging (fMRI) protocol.

METHODS

This comparative study included 12 healthy women (mean age 53.17 ± 4.93 years) and 12 women with fecal incontinence (56.25 ± 6.94 years). An MRI-compatible anal manometer was used to register voluntary external anal sphincter contraction. During brain fMRI imaging, participants were cued to perform 10-s series of self-paced anal sphincter contractions at an approximate rate of 1 Hz. Brain structures linked to anal sphincter contractions were mapped and the findings were compared between the 2 study groups.

KEY RESULTS

There were no differences in the evoked brain activity between the 2 groups. In healthy women, group fMRI analysis revealed significant activations in medial primary motor cortices, supplementary motor area, bilateral putamen, and cerebellum, as well as in the supramarginal gyrus and visual areas. In patients with fecal incontinence, the activation pattern involved similar regions without significant differences with healthy women.

CONCLUSIONS & INFERENCES

This brain fMRI-anorectal protocol was able to map the brain regions linked to voluntary anal sphincter function in healthy and women with fecal incontinence.

Human studies of anorectal sensory function

This review addresses three main questions: (1) Why is anorectal sensory function important in humans? (2) What is the evidence for anorectal sensory dysfunction in disease? (3) Can anorectal sensory function be modified for therapeutic benefit?

Microstructural white matter brain abnormalities in patients with idiopathic fecal incontinence

BACKGROUND

Abnormal central nervous system processing of visceral sensation may be a part of the pathogenesis behind idiopathic fecal incontinence (IFI). Our aim was to characterize brain differences in patients with IFI and healthy controls by means of structural magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI).

METHODS

In 21 female patients with IFI and 15 female healthy controls, whole-brain structural differences in gray matter volume (GMV), cortical thickness, and white matter tracts fractional anisotropy (FA) were quantified. For this purpose, we used voxel-based morphometry, surface based morphometry and tract-based spatial statistic, respectively. Furthermore, associations between structural brain characteristics and latencies of rectal sensory evoked electroencephalography potentials were determined.

KEY RESULTS

Compared to healthy controls, IFI patients had significantly reduced FA values, reflecting reduced white matter tract integrity, in the left hemisphere superior longitudinal fasciculus (SLF), posterior thalamic radiation, and middle frontal gyrus (MFG), all P<.05. No differences were observed in GMV or in cortical thickness. The reduced FA values in the SLF and MFG were correlated with prolonged latencies of cortical potentials evoked by rectal stimuli (all P<.05).

CONCLUSIONS & INFERENCES

This explorative study suggests that IFI patients have no macrostructural brain changes, but exhibit microstructural changes in white matter tracts relevant for sensory processing. The clinical relevance of this finding is supported by its correlations with prolonged latencies of cortical potentials evoked by rectal stimulation. This supports the theories of central nervous system changes as part of the pathogenesis in IFI patients.

Transcutaneous sacral nerve stimulation for intraoperative verification of internal anal sphincter innervation

BACKGROUND

The current standard for pelvic intraoperative neuromonitoring (pIONM) is based on intermittent direct nerve stimulation. This study investigated the potential use of transcutaneous sacral nerve stimulation for non-invasive verification of pelvic autonomic nerves.

METHODS

A consecutive series of six pigs underwent low anterior rectal resection. For transcutaneous sacral nerve stimulation, an array of ten electrodes (cathodes) was placed over the sacral foramina (S2 to S4). Anodes were applied on the back, right and left thigh, lower abdomen, and intra-anally. Stimulation using the novel method and current standard were performed at different phases of the experiments under electromyography of the autonomic innervated internal anal sphincter (IAS).

KEY RESULTS

Transcutaneous stimulation induced increase of IAS activity could be observed in each animal under specific cathode-anode configurations. Out of 300 tested configurations, 18 exhibited a change in the IAS activity correlated with intentional autonomic nerve damage. The damage resulted in a significant decrease of the relative area under the curve of the IAS frequency spectrum (P<.001). Comparison of the IAS spectra under transcutaneous and direct stimulation revealed no significant difference (after rectal resection: median 5.99 μV•Hz vs 7.78 μV•Hz, P=.12; after intentional nerve damage: median -0.27 μV•Hz vs 3.35 μV•Hz, P=.29).

CONCLUSIONS AND INFERENCES

Non-invasive selective transcutaneous sacral nerve stimulation could be used for verification of IAS innervation.

Sacral Neuromodulation for Fecal Incontinence: A Review of the Central Mechanisms of Action

OBJECTIVE

Fecal incontinence (FI) has a devastating effect on the quality of life and results in social isolation. Sacral neuromodulation (SNM) is proven to be an effective, minimal invasive treatment modality for FI. Despite the increasing application of SNM, the exact mechanisms of action remain unclear. The initial assumption of peripheral motor neurostimulation is not supported by increasing evidence, which report effects of SNM outside the pelvic floor. A new hypothesis states that afferent signals to the brain are essential for a successful therapy. This study aimed to review relevant studies on the central mechanism of SNM in FI.

METHODS

Clinical and experimental studies on the central mechanisms, both brain and spinal cord, of SNM for FI up to December 2015 were evaluated.

RESULTS

In total, 8 studies were found describing original data on the central mechanism of SNM for FI. Four studies evaluated the central effects of SNM in a clinical setting and 4 studies evaluated the central effects of SNM in an experimental animal model. Results demonstrated a variety of (sub)cortical and spinal changes after induction of SNM.

CONCLUSION

Review of literature demonstrated evidence for a central mechanism of action of SNM for FI. The corticoanal pathways, brainstem, and specific parts of the spinal cord are involved.

A pilot study assessing the efficacy of posterior tibial nerve stimulation in the treatment of low anterior resection syndrome

BACKGROUND

Low anterior resection for rectal cancer often results in severe bowel dysfunction, specifically low anterior resection syndrome (LARS), with symptoms such as incontinence, urgency, and frequent bowel movements. Percutaneous tibial nerve stimulation (PTNS) resulted in a high rate of success in patients with fecal incontinence. The aim of this study was to evaluate the effectiveness of treatment with PTNS in LARS and to identify predictors of the outcome of the technique.

METHODS

The study was conducted from May 2012 to April 2015 at the Alvaro Cunqueiro Hospital, University Hospital Complex of Vigo, Spain. Ten patients with LARS were recruited consecutively. All patients underwent 2 sessions per week (30 min each one) for 6 weeks. Patients were followed for 3 weeks, and those who had a significant clinical improvement were recruited to a second phase of PTNS. Some patients presenting with relapse during follow-up underwent an additional phase of PTNS. Outcome measures included Wexner scores, quality of life scores, and urgency of defecation.

RESULTS

Three patients did not complete the treatment due to poor response in the first phase. Incontinence was reduced in the remaining seven of ten patients. The median Wexner score at initial patient evaluation was 14 (IQR 10.75-18.5), which decreased to 10 (IQR 6.5-18) after treatment (p = 0.034). A statistically significant improvement was demonstrated in quality of life scale, lifestyle, depression, and daily defecation urgency (p < 0.05). LARS Score improvement was observed in five patients (50%) with a total resolution of LARS in 2 (20%).

CONCLUSIONS

PTNS is an ambulatory treatment that could play an important role in the context of a multimodal treatment approach in patients with LARS. It could be a first-line treatment to identify non-responders to conservative management who need different and more invasive treatments.

Increased yield pressure in the anal canal during sacral nerve stimulation: a pilot study with the functional lumen imaging probe

BACKGROUND

Sacral nerve stimulation (SNS) is a well-established treatment for fecal incontinence but its mode of action remains obscure. Anal sphincter function is usually evaluated with manometry but resistance to distension may be a more appropriate parameter than luminal pressure. The functional lumen imaging probe allows detailed description of distension properties of the anal canal. Our objective in this study was to characterize the impact of SNS on distension properties of the anal canal in patients with idiopathic fecal incontinence.

METHODS

We studied 10 women (median age 64 [44-79] years) with idiopathic fecal incontinence at baseline and during SNS. The luminal geometry of the anal canal was examined with the FLIP at rest and during squeeze and the distensibility of the anal canal was investigated during filling of the bag.

KEY RESULTS

All patients were successfully treated with SNS and the mean Wexner Incontinence Score was reduced from 14.9 ± 4 to 7.1 ± 4.8 (P<.001). The pressure required to open the narrowest point of the anal canal during distension (yield pressure) increased from 14.5 ± 12.2 mmHg at baseline to 20.5 ± 13.3 mmHg during SNS (P<.01). The pressure-strain elastic modulus increased non-significantly from 2.2 ± 0.5 to 2.9 ± 1.6 kPa, indicating increased stiffness of the anal canal.

CONCLUSION AND INFERENCES

The yield pressure and the resistance to distension increased in response to SNS for idiopathic fecal incontinence. This will inevitably increase the resistance to flow through the anal canal, which may contribute to the benefits of sacral nerve stimulation.

Three-year follow-up of sacral nerve stimulation for patients with diarrhoea-predominant and mixed irritable bowel syndrome

AIM

Our unit has recently shown that sacral nerve stimulation (SNS) has a significantly positive short-term effect on selected patients with diarrhoea-predominant or mixed irritable bowel syndrome (IBS). The aim of the present prospective study was to evaluate the medium-term efficacy of SNS for IBS to establish whether SNS could have a future role in the treatment of IBS.

METHOD

Patients with IBS who had previously been implanted with a permanent neurostimulator as part of a randomized, controlled, crossover study, were assessed for medium-term follow-up. The primary end-point was change in the IBS-specific symptom score (Gastrointestinal Symptom Rating Scale-Irritable Bowel Syndrome version questionnaire) from baseline to 3-year follow-up. The secondary end-point was a change in the IBS-specific quality of life score (Irritable Bowel Syndrome-Impact Scale questionnaire) from baseline to 3-year follow-up.

RESULTS

Of 26 patients, 20 were eligible for 3-year follow-up. The median IBS-specific symptom score was significantly lower at 3-year follow-up (30, range 13-71) than at baseline (62, 45-80) (P = 0.0001). The effect was observed in all symptom clusters within the score. Also, the median IBS-specific quality of life score was significantly improved at 3-year follow-up (52, 26-169) compared with baseline (135, 82-180, P = 0.0002). The effect was observed in all domains of the score. As per the protocol, 75% of patients were judged therapeutic successes. Seventy per cent of patients had a more than 50% reduction in daily IBS symptoms.

CONCLUSION

At medium-term follow-up, SNS continues to be an effective treatment for highly selected patients with diarrhoea-predominant or mixed IBS.

Does Sacral Nerve Stimulation Improve Continence Through Enhanced Sensitivity of the Anal Canal? A Pilot Study

BACKGROUND

It has been suggested that the effects of sacral nerve stimulation against fecal incontinence involve neuromodulation at spinal or supraspinal levels.

OBJECTIVE

This study aims to investigate the afferent sensory pathways from the anorectum before and during sacral nerve stimulation.

DESIGN

This is an explorative study.

PATIENTS

Fifteen women with idiopathic fecal incontinence (mean age, 58 ± 12.2 years) were selected.

INTERVENTIONS

Cortical evoked potentials were recorded during repeated rapid balloon distension of the rectum and the anal canal both before and during temporary sacral nerve stimulation. Stimuli applied were individualized according to the subjective urge to defecate.

MAIN OUTCOME MEASURES

The main outcomes measured were 1) stimulus intensity, 2) latencies and amplitudes of cortical evoked potentials, and 3) spectral content in predefined frequency bands of cortical evoked potentials.

RESULTS

The median Wexner fecal incontinence score improved from 15.5 ± 3.6 before to 6.7 ± 5 during sacral nerve stimulation (p < 0.001). Sacral nerve stimulation did not affect the threshold for urge to defecate during rectal distension (p = 0.64) but reduced the threshold from stimulation of the anal canal by 50% (p = 0.03). No statistically significant differences were found in latencies, amplitudes, or spectral analysis.

LIMITATIONS

This is a pilot study of limited size.

CONCLUSIONS

In patients with idiopathic fecal incontinence, sacral nerve stimulation reduced the threshold for urge to defecate elicited from the anal canal, whereas supraspinal responses remained unaltered. This may suggest that sacral nerve stimulation, at least in part, acts via somatic afferent fibers enhancing anal sensation.

Reversal of sensory deficit through sacral neuromodulation in an animal model of fecal incontinence

BACKGROUND

Sacral neuromodulation (SNM) is a treatment option for intractable fecal incontinence. The mechanism of action is unclear, however, increasing evidence for afferent somatosensory effects exists. This study's aim was to elucidate effects of acute SNM on the cerebral cortex in a rodent model of pudendal nerve injury.

METHODS

The effects of 14 Hz and 2 Hz SNM on sensory cortical activation were studied. In 32 anesthetized rats, anal canal evoked potentials (EPs) were recorded over the primary somatosensory cortex. Pudendal nerve injury was produced by 1-hour inflation of two intra-pelvic balloons. Four groups were studied: balloon injury, balloon injury plus either 14 Hz or 2 Hz SNM, sham operation. Immunohistochemistry for the neural plasticity marker polysialylated neural cell adhesion molecule (PSA-NCAM) positive cells (numerical density and location) in the somatosensory cortex was performed.

KEY RESULTS

Anal EP amplitudes diminished during balloon inflation; 14 Hz SNM restored diminished anal EPs to initial levels and 2 Hz SNM to above initial levels. Evoked potential latencies were prolonged during balloon inflation. The numerical density of PSA-NCAM positive cells increased in the SNM groups, but not in sham or balloon injury without SNM. Stimulated cortices showed clusters of PSA-NCAM positive cells in layers II, IV, and V. Post SNM changes were similar in both SNM groups.

CONCLUSIONS & INFERENCES

Sacral neuromodulation augments anal representation in the sensory cortex and restores afferent pathways following injury. PSA-NCAM positive cell density is increased in stimulated cortices and positive cells are clustered in layers II, IV, and V.

Bilateral compared with unilateral sacral nerve stimulation for faecal incontinence: results of a randomized, single-blinded crossover study

AIM

This randomized single-blinded crossover study aimed to investigate whether bilateral sacral nerve stimulation (SNS) is more efficient than unilateral stimulation for faecal incontinence (FI).

METHOD

Patients with FI who responded during a unilateral test stimulation, with a minimum improvement of 50% were eligible. Twenty-seven patients who were accepted to enter the trial were bilaterally implanted with two permanent leads and pacemakers. Patients were randomized into three periods of 4 weeks' stimulation including unilateral right, unilateral left and bilateral stimulation. Symptoms scores and bowel habit diaries were collected at baseline and in each study period. A 1-week washout was introduced between each study period.

RESULTS

Twenty-seven (25 female) patients with a median age of 63 (36-84) years were bilaterally implanted from May 2009 to June 2012. The median number of episodes of FI per 3 weeks significantly decreased from 17 (3-54) at baseline to 2 (0-20) during stimulation on the right side, 2 (0-42) during stimulation on the left side and 1 (0-25) during bilateral stimulation. The Wexner incontinence score improved significantly from a median of 16 (10-20) at baseline to 9 (0-14) with right-side stimulation, 10 (0-15) with left-side stimulation and 9 (0-14) with bilateral stimulation. The differences between unilateral right or unilateral left and bilateral stimulation were non-significant, for FI episodes (P = 0.3) or for Wexner incontinence score (P = 0.9).

CONCLUSION

Bilateral SNS therapy for FI is not superior to standard unilateral stimulation in the short term. Equal functional results can be obtained regardless of the side of implantation.

Diagnosis and treatment of faecal incontinence: Consensus statement of the Italian Society of Colorectal Surgery and the Italian Association of Hospital Gastroenterologists

Faecal incontinence is a common and disturbing condition, which leads to impaired quality of life and huge social and economic costs. Although recent studies have identified novel diagnostic modalities and therapeutic options, the best diagnostic and therapeutic approach is not yet completely known and shared among experts in this field. The Italian Society of Colorectal Surgery and the Italian Association of Hospital Gastroenterologists selected a pool of experts to constitute a joint committee on the basis of their experience in treating pelvic floor disorders. The aim was to develop a position paper on the diagnostic and therapeutic aspects of faecal incontinence, to provide practical recommendations for a cost-effective diagnostic work-up and a tailored treatment strategy. The recommendations were defined and graded on the basis of levels of evidence in accordance with the criteria of the Oxford Centre for Evidence-Based Medicine, and were based on currently published scientific evidence. Each statement was drafted through constant communication and evaluation conducted both online and during face-to-face working meetings. A brief recommendation at the end of each paragraph allows clinicians to find concise responses to each diagnostic and therapeutic issue.

Abnormal neuronal response to rectal and anal stimuli in patients with idiopathic fecal incontinence

BACKGROUND

The pathophysiology behind idiopathic fecal incontinence (IFI) is poorly understood. We hypothesized abnormal sensory pathways along the brain-gut axis as a key player in this disease, reflected in cortical evoked potentials (CEP) from mechanical stimuli of the rectum and the anal canal.

METHODS

CEPs were recorded during repeated rapid balloon distensions of the rectum and anal canal in 19 women with IFI (mean age: 60 ± 14, mean Wexner score: 14.7 ± 2.9) and in 19 healthy women (mean age: 56 ± 11, mean Wexner score: 1.1 ± 1.3). Latencies, amplitudes and topography of CEPs elicited by rectal distension were compared between the groups. CEPs from both rectal and anal distensions were examined using spectral band analysis of single sweeps determining the relative amplitude of five spectral bands as a proxy of neuronal processing.

KEY RESULTS

Compared to controls IFI patients had prolonged latency of CEPs from rectal distension by up to 27% (p < 0.001) while amplitudes and topography were similar (all p > 0.7 and all p > 0.23). Spectral analysis of CEPs from rectal distensions showed no difference (all p > 0.1) between groups. However, analysis of CEPs following distension of the anal canal resulted in abnormally low activity in beta (8-12 Hz; p < 0.001) band and high activity in the gamma (32-70 Hz; p = 0.04) band in patients.

CONCLUSIONS & INFERENCES

IFI seems to be associated with impaired ano-rectal sensory functions in both the afferent fibers to the brain and the cortical processing of anal sensory pathways. This may play a central role for the pathogenesis of IFI.

Sacral nerve stimulation for faecal incontinence and constipation: a European consensus statement

AIM

In Europe during the last decade sacral nerve stimulation (SNS) or sacral neuromodulation (SNM) has been used to treat faecal incontinence (FI) and constipation. Despite this, there is little consensus on baseline investigations, patient selection and operative technique. A modified Delphi process was conducted to seek consensus on the current practice of SNS/SNM for FI and constipation.

METHOD

A systematic literature search of SNS for FI and constipation was conducted using PubMed. A set of questions derived from the search and expert opinion were answered on-line on two occasions by an international panel of specialists from Europe. A 1-day face-to-face meeting of the experts finalized the discussion.

RESULTS

Three hundred and ninety-three articles were identified from the literature search, of which 147 fulfilled the inclusion criteria. Twenty-two specialists in FI and constipation from Europe participated. Agreement was achieved on 43 (86%) of 50 domains including the set-up of service, patient selection, baseline investigations, operative technique and programming of the device. The median of agreement was 95% (35-100%).

CONCLUSION

Consensus was achieved on the majority of domains of SNS/SNM for FI and constipation. This should serve as a benchmark for safe and quality practice of SNS/SNM in Europe.

Sacral nerve stimulation changes rectal sensitivity and biomechanical properties in patients with irritable bowel syndrome

BACKGROUND

Sacral nerve stimulation (SNS) has been demonstrated to alleviate symptoms and improve quality of life in selected patients with irritable bowel syndrome (IBS). The mechanisms of action, however, remain unknown. The aim of the study was to evaluate the effects of SNS on rectal sensitivity and biomechanical properties in patients with IBS.

METHODS

Twenty patients with diarrhea-predominant (n = 11) or mixed (n = 9) IBS were treated with SNS in a controlled, randomized crossover trial. They were randomized to either 1 month of SNS (ON) or placebo (OFF) with the opposite setting for the next month. Sensory and biomechanical parameters were assessed by multimodal rectal stimulation at the end of each period. IBS-specific symptoms were evaluated at baseline and at the end of each treatment period.

KEY RESULTS

Cold stimuli were better tolerated in the ON period (19.9 °C[± 0.6]) compared to the OFF period (21.8 °C[± 0.6]; p = 0.03). Significantly lower cross-sectional areas were needed to elicit sensory responses in the ON period (1545 mm(2) [± 95]) compared to the OFF period (1869 mm(2) [± 92]; p = 0.015). The association between reduced sensory threshold and improvement of constipation was of borderline significance (p = 0.05). Wall stiffness was significantly lower in the ON period (192 mmHg[± 10]) compared to the OFF period (234 mmHg[± 10]; p = 0.004). Reduced wall stiffness was significantly associated with improved overall GSRS-IBS symptom score (p = 0.01). Reduced sensory threshold to stretch (p = 0.02) and reduced wall stiffness (p < 0.001) were predictors of the GSRS-IBS symptom score.

CONCLUSIONS & INFERENCES

SNS for diarrhea-predominant and mixed IBS relaxes the rectal wall, while making it more sensitive to stretch and less sensitive to cold. Reduced wall stiffness and increased sensitivity to stretch are associated with improved GSRS-IBS symptom score.

A systematic review of sacral nerve stimulation mechanisms in the treatment of fecal incontinence and constipation

BACKGROUND

Sacral nerve stimulation (SNS) is now well established as a treatment for fecal incontinence (FI) resistant to conservative measures and may also have utility in the management of chronic constipation; however, mechanism of action is not fully understood. End organ effects of SNS have been studied in both clinical and experimental settings, but interpretation is difficult due to the multitude of techniques used and heterogeneity of reported findings. The aim of this study was to systematically review available evidence on the mechanisms of SNS in the treatment of FI and constipation.

METHODS

Two systematic reviews of the literature (performed in accordance with the Preferred Reporting Items for Systematic reviews and Meta-Analyses framework) were performed to identify manuscripts pertaining to (a) clinical and (b) physiological effects of SNS during the management of hindgut dysfunction.

KEY RESULTS

The clinical literature search revealed 161 articles, of which 53 were deemed suitable for analysis. The experimental literature search revealed 43 articles, of which nine were deemed suitable for analysis. These studies reported results of investigative techniques examining changes in cortical, gastrointestinal, colonic, rectal, and anal function.

CONCLUSIONS & INFERENCES

The initial hypothesis that the mechanism of SNS was primarily peripheral motor neurostimulation is not supported by the majority of recent studies. Due to the large body of evidence demonstrating effects outside of the anorectum, it appears likely that the influence of SNS on anorectal function occurs at a pelvic afferent or central level.

Effects of stimulation frequency and intensity in sacral neuromodulation on anorectal inputs to the somatosensory cortex in an experimental model

Introduction

Although sacral neuromodulation (SNM) is an established treatment for faecal incontinence, stimulation parameters have been derived empirically and only one frequency (14 Hz) is employed clinically. The aim of this study was to test a range of stimulation frequencies to establish an optimal frequency of SNM for maximum augmentation of anal canal cortical evoked potentials (EPs) in an animal model.

Methods

In female Wistar rats, anal canal EPs were recorded over the primary somatosensory cortex using a flexible multielectrode array, and the effect of SNM was studied. SNM was applied at 0·1–100 Hz and a frequency response curve plotted. The data were fitted to a quadratic equation.

Results

The magnitude of potentiation of anal canal EPs caused by SNM depended significantly on stimulation frequency (P &lt; 0·001). The frequency–potentiation relationship was parabolic in form, with a clear optimum at 2 Hz. The SNM must be applied for at least 3 min. The theoretical maximal potentiation predicted by the model was not found to be statistically different to actual data recorded (P = 0·514–0·814). The response depended on stimulation amplitude in an ‘all-or-nothing’ fashion. EPs were augmented when the SNM intensity was 0·5 times the motor threshold to tail twitch or greater, but values below this intensity failed to affect the EPs.

Conclusion

The effect of SNM in this animal model is governed principally by frequency, with an optimum of 2 Hz. If animal data can be translated to humans, optimization of SNM frequency may offer a clinically relevant improvement in the efficacy of SNM.

Outcome of sacral nerve stimulation for fecal incontinence at 5 years

OBJECTIVE

This study aimed to evaluate the outcome of sacral nerve stimulation (SNS) for fecal incontinence at 5 years after implantation and to identify predictors of sustained efficacy.

BACKGROUND

There is a lack of knowledge about the long-term outcome of SNS for fecal incontinence.

METHODS

Prospectively collected data from patients who underwent implantation of an SNS device between 2001 and 2006 were reviewed.

RESULTS

One hundred and one patients were available for outcome evaluation at 5 years. Sixty of 101 patients [42.6% on intention-to-treat (ITT) and 55.6% per protocol (PP)] reported a favorable outcome, 41 patients (ITT 29.1%; PP 38.0%) reported an unfavorable outcome, of whom 24 patients (ITT 17.0%; PP 22.2%) had their device explanted or permanently switched off before 5 years. Wexner incontinence scores improved significantly from a baseline median of 16 (range 6-20) to a median of 6 (range 0-20) at 3 months (P < 0.0001), and the improvement compared with baseline was maintained throughout the 5-year follow-ups (P < 0.0001).Age was a negative predictive factor [odds ratio (OR): 0.96 each year increase, 95% confidence interval (CI): 0.92-0.99; P = 0.016]. Positive predictors included improvement of urge incontinence episodes during percutaneous nerve evaluation (OR: 10.8; 95% CI: 1.72-132; P = 0.036), improvement of incontinence scores at 6 months from baseline (OR: 6.29; 95% CI: 1.33-34.3; P = 0.025), particularly improvement of incontinence scores from 3 to 6 months (OR: 41.5; 95% CI: 3.51-811; P = 0.007). Overall, 521 reportable events were recorded from 94 patients (93.1%).

CONCLUSIONS

On an ITT analysis, 42.6% of patients reported favorable outcomes at 60 months. Patient's age, improvement of urge incontinence during PNE, and sustained efficacy during the first 6 months after implantation are some of the predictors identified.

A randomised, controlled study of small intestinal motility in patients treated with sacral nerve stimulation for irritable bowel syndrome

Background

Irritable bowel syndrome (IBS) is among the most common gastrointestinal disorders worldwide. In selected patients with severe diarrhoea-predominant or mixed IBS subtypes sacral nerve stimulation (SNS) alleviates IBS-specific symptoms and improves quality of life. The mode of action, however, remains unknown. The present study aimed to evaluate the effect of SNS on small intestinal motility in IBS patients.

Methods

Twenty patients treated with SNS for severe diarrhoea-predominant or mixed IBS were included in a randomised, controlled, crossover study. The neurostimulator was turned ON or OFF for the first one month and then to the opposite setting for the next month. Gastrointestinal transit patterns were investigated with the Motility Tracking System-1 (MTS-1) at the end of each the ON and OFF period. Primary endpoint was change in the velocity of the magnetic pill within the small intestine. Statistical testing was performed with Wilcoxon’s rank sum test and Fisher’s exact test.

Results

The median velocity of the magnetic pill through the small intestine in the fasting state was not significantly different between periods with and without SNS (Group ON-OFF: median change 0 m/h (range -1.07, 0.63), Group OFF-ON: median change 0.27 m/h (range -0.59, 1.12)) (p = 0.25). Neither, was the median velocity of the magnetic pill through the small intestine in the postprandial state significantly different between periods with and without SNS (Group ON-OFF: median change -0.13 m/h (range -0.46, 0.23), Group OFF-ON: median change 0.015 m/h (range -0.48, 0.59)) (p = 0.14).

Conclusion

Even though SNS may reduce symptoms of diarrhoea-predominant and mixed IBS, it has no detectable effect on small intestinal transit patterns.

Trial registration

Clinical.trials.gov, (NCT00919672).

A pilot study of chronic pudendal nerve stimulation for faecal incontinence for those who have failed sacral nerve stimulation

BACKGROUND

Sacral nerve stimulation (SNS) is used as a first-line treatment for faecal incontinence when conservative measures have failed. However, one-third of patients fail to benefit from this treatment. We hypothesised that sacral afferent stimulation can be maximised using pudendal nerve stimulation (PNS) and this may be of benefit in this patient group. The aim of this study was to assess chronic PNS for those who failed to improve with SNS.

METHODS

Ten patients who had failed SNS were recruited. All underwent percutaneous insertion of a stimulation lead with four-electrode array adjacent to the pudendal nerve. Continuous bipolar stimulation was administered using an external pulse generator over a 3-week period. Those who experienced a ≥50% reduction in the frequency of incontinent episodes over this period proceeded to chronic stimulation with an implantable pulse generator.

RESULTS

Five patients experienced a ≥50% reduction of incontinent episodes during test stimulation and proceeded to chronic stimulation. In these five patients, at a median (range) follow-up of 24 (6-36) months, the median (inter quartile range) frequency of incontinent episodes reduced from 5 (18.25) to 2.5 (3) per week (p = 0.043). Three patients maintained a ≥50% improvement in soiling. There was an improvement in the St Mark's continence Score from 19 (15-24) to 16 (13-19), p = 0.042. There were no significant changes in ability to defer defecation or in quality of life scores.

CONCLUSIONS

Pudendal nerve stimulation failed to improve the symptoms in the majority of patient who had failed SNS. Only a third experienced any improvement.

Cortical evoked potentials in response to rapid balloon distension of the rectum and anal canal

BACKGROUND

Neurophysiological evaluation of anorectal sensory function is hampered by a paucity of methods. Rapid balloon distension (RBD) has been introduced to describe the cerebral response to rectal distension, but it has not successfully been applied to the anal canal.

METHODS

Nineteen healthy women received 30 RBDs in the rectum and the anal canal at intensities corresponding to sensory and unpleasantness thresholds, and response was recorded as cortical evoked potentials (CEPs) in 64-channels. The anal canal stimulations at unpleasantness level were repeated after 4 min to test the within-day reproducibility. CEPs were averaged, and to overcome latency variation related to jitter the spectral content of single sweeps was also computed.

KEY RESULTS

Repeated stimulation of the anal canal generated CEPs with similar latencies but smaller amplitudes compared to those from the rectum. Due to latency jitter, reproducibility of averaged CEPs was lower than what was found in the rectum. The most reproducible feature was N2P2 peak-to-peak amplitude with intra-class correlation coefficient (ICC) of 0.7 and coefficient of variation (CV) of 18%. Spectral content of the single sweeps showed reproducibility with ICCs for all bands >0.8 and corresponding CVs <7%.

CONCLUSIONS & INFERENCES

Cortical potentials evoked from the anal canal are challenged by latency jitter likely related to variability in muscle tone due to the distensions. Using single-sweep analysis, anal CEPs proved to be reproducible and should be used in future evaluation of the anal function.

Percutaneous nerve evaluation based on electrode placement under control of autonomic innervation

BACKGROUND

Foramen needle electrode placement for percutaneous nerve evaluation (PNE) is currently carried out while observing the somatic motor response. This study investigated electrode placement while observing the autonomic as well as the somatic response.

METHODS

A consecutive series of ten patients (seven women) with a median age of 51.9 (range 30-75) years undergoing PNE for faecal incontinence (n = 6) and obstipation (n = 4) were investigated prospectively. Electrode placement was carried out under simultaneous electromyography (EMG) of the external anal sphincter (EAS) and internal anal sphincter (IAS) and cystomanometry.

RESULTS

PNE under control of somatic and autonomic nerve responses was carried out in all patients. In three out of ten patients, initial needle electrode placement showed single evoked EMG signals from the EAS. Final electrode placement resulted in adequate somatic motor and autonomic responses in all patients. Comparison of the increases in IAS EMG amplitude on the right and left stimulation sites for sacral nerves S3 and S4 demonstrated significant differences [S3 right: median 15.3 (interquartile range (IQR) 10.4; 20.1) µV vs. S3 left: median 11.6 (IQR 8.6; 16.0) µV, p = 0.034 and S4 right: median 24.1 (IQR 20.1; 37.2) µV vs. S4 left: median 12.0 (IQR 10.7; 13.7) µV, p = 0.012]. Stimulation-induced bladder activation was achieved in all seven patients with concomitant urinary dysfunction.

CONCLUSIONS

Control of not just the somatic motor response but also the autonomic nerve response during foramen needle electrode placement may objectify PNE.

The effects of sacral nerve stimulation on continence are temporarily maintained after turning the stimulator off

AIM

Sacral nerve stimulation is an effective treatment for urinary and faecal incontinence even though its mechanism of action is uncertain. Central nervous system involvement by 'setting-up' neurological mechanisms appointed to control pelvic function has been hypothesized. The study aimed to evaluate whether the effects of long-term sacral nerve stimulation are memorized and therefore maintained after switching off the stimulator.

METHOD

Patients having sacral nerve stimulation for faecal and/or urinary incontinence for at least 1 year had the stimulator turned off and the results monitored. Data recorded with the stimulator off were compared with post-implant data. If symptoms recurred the stimulator was switched back on. Nineteen patients entered the study. Fourteen had faecal and/or urinary incontinence and five had faecal incontinence alone. The symptoms were assessed by means of a bowel function diary and dedicated questionnaire.

RESULTS

In 10 patients symptoms recurred at different intervals after a median off period of 3.4 months with a probability of symptom relapse of 55%. The Fecal Incontinence Quality of Life (FIQL) score did not show any significant difference in nine patients with the stimulator off for at least 1 year. No factors predictive of symptom recurrence were identified although an idiopathic aetiology, severity of disease and urinary incontinence had higher hazard ratios. During the off period, none of the scores and episodes of incontinence showed significant changes compared with the on period.

CONCLUSION

The effects of sacral nerve stimulation on faecal and urinary incontinence were maintained in about half of patients after switching the stimulator off, but in some symptoms returned after different periods of time. The data shed new light on possible effects of sacral nerve stimulation on brain neuroplasticity in the control of continence.

A review of posterior tibial nerve stimulation for faecal incontinence

AIM

This review aimed to assess the published results of posterior tibial nerve stimulation (PTNS) for faecal incontinence.

METHOD

A search was performed of PubMed, MEDLINE and Embase to identify studies describing the clinical outcome of PTNS for faecal incontinence.

RESULTS

Thirteen studies were identified. These described the outcome of PTNS for faecal incontinence in 273 patients. Four described transcutaneous PTNS, eight percutaneous PTNS and one compared both methods of PTNS with a sham transcutaneous group. One investigated patients with faecal incontinence and spinal cord injury and another with inflammatory bowel disease. There was marked heterogeneity of the treatment regimens and of the end points used. All reported that PTNS improved faecal incontinence. A > 50% improvement was reported in episodes of faecal incontinence in 63-82% of patients. An improvement was seen in urgency (1-5 min). Improvement was also described in the Cleveland Clinic faecal incontinence score in eight studies. Patients with urge and mixed incontinence appear to benefit more than those with passive incontinence. Treatment regimens ranged in duration from 1-3 months. A residual therapeutic effect is seen after completion of treatment. Follow-up ranged from 1-30 months.

CONCLUSION

PTNS is effective for faecal incontinence. However, many of the published studies are of poor quality. Comparison between studies is difficult owing to differences in the outcome measures used, technique of PTNS and the timing and duration of treatment.

Sacral neuromodulation for bowel dysfunction: a consensus statement from the Italian group

BACKGROUND

Representatives from the Italian centers experienced in sacral neuromodulation (SNM) for the treatment of bowel dysfunction met in order to define the current clinical practice in Italy and to produce a consensus statement regarding indications for this therapy and patient management.

METHODS

Fifty Italian colonproctologists were asked to complete a questionnaire concerning their clinical practice in SNM (290 questions, grouped within 4 broad areas). Physicians expressed their opinion by completing the questionnaire, assigning to each statement their level of agreement according to the 5-point Likert scale; the data were analyzed by attributing to each expert's answers a weight proportional to the degree of experience. During a meeting held 2 months later, the critical aspects of the therapy were re-examined and discussions held with the goal of reaching an agreement on controversial topics. The available literature was reviewed.

RESULTS

Patient selection criteria, etiology, diagnostic investigations, test procedures and implantation, follow-up and evaluation of results have been reviewed. The aim was to achieve an algorithm for patient management, showing the place of SNM in the treatment of bowel dysfunction. The approach in case of treatment failure was also discussed.

CONCLUSIONS

Analysis of the data collected reveals substantial consensus at the national level concerning all the main points with regard to the therapy. The recommendations expressed in this article can be considered as national guidelines and taken into account by the principal international implantation centers.

Sacral nerve stimulation for constipation

BACKGROUND

For over 10 years sacral nerve stimulation (SNS) has been used for patients with constipation resistant to conservative treatment. A review of the literature is presented.

METHODS

PubMed, MEDLINE and Embase databases were searched for studies demonstrating the use of SNS for the treatment of constipation.

RESULTS

Thirteen studies have been published describing the results of SNS for chronic constipation. Of these, three were in children and ten in adults. Test stimulation was successful in 42-100 per cent of patients. In those who proceeded to permanent SNS, up to 87 per cent showed an improvement in symptoms at a median follow-up of 28 months. The success of stimulation varied depending on the outcome measure being used. Symptom improvement correlated with improvement in quality of life and patient satisfaction scores.

CONCLUSION

SNS appears to be an effective treatment for constipation, but this needs to be confirmed in larger prospective studies with longer follow-up. Improved outcome measures need to be adopted given the multiple symptoms that constipation may be associated with. Comparison with other established surgical therapies also needs consideration.

Turning off sacral nerve stimulation does not affect gastric and small intestinal motility in patients treated for faecal incontinence

AIM

Sacral nerve stimulation (SNS) reduces symptoms in up to 80% of patients with faecal incontinence (FI). Its effects are not limited to the distal colon and the pelvic floor. Accordingly, spinal or supraspinal neuromodulation have been suggested as part of the mode of action. The effect of SNS on gastric and small-intestinal motility was studied.

METHOD

Using the magnet tracking system, MTS-1, a small magnetic pill was tracked twice through the upper gastrointestinal tract of eight patients with FI successfully treated with SNS. Following a randomized double-blind crossover design, the stimulator was either left active or was turned off for 1 week before investigations with MTS-1.

RESULTS

The median (range) frequency of gastric con-tractions was 3.05 (2.83-3.40) per min during SNS and 3.04 (2.79?-3.76) per min without (P=NS). The median (range) frequency of contractions in the small intestine during the first 2h after pyloric passage was 10.005 (9.68-10.70) per min during SNS and 10.09 (9.79-10.29) per min without SNS (P=NS). The median (range) velocity of the magnetic pill during the first 2h in the small intestine was 1.6 (1.2-2.8) cm/min during SNS and 1.7 (0.8-3.7) cm/min without SNS (P=NS). Small-intestinal propagation mainly occurred during very fast movements (>15cm/min), accounting for 51% (42-60%) of the distance 3% (2-4%) of the time during SNS and for 53% (18-73%) of the distance 3% (1-8%) of the time without SNS (P=NS).

CONCLUSION

Turning off SNS for 1week did not affect gastric or small-intestinal motility patterns.

Randomized double-blind crossover study of alternative stimulator settings in sacral nerve stimulation for faecal incontinence

Background

Sacral nerve stimulation is an established treatment for faecal incontinence. Nearly half of all patients experience loss of efficacy at some point. Standard reprogramming restores efficacy for some, but not all, patients. This study aimed to determine whether alternative stimulator settings would increase treatment efficacy.

Methods

Patients with sustained loss of efficacy were recruited from two international specialist centres. A number of alternative stimulation parameters were tested using a double-blind randomized crossover study design. Stimulation settings tested were pulse frequencies of 6·9 and 31 Hz, and pulse widths of 90 and 330 µs, compared with one standard setting of 14 Hz/210 µs. Treatment efficacy was evaluated using a disease-specific quality-of-life score (Fecal Incontinence Quality of Life Scale, FIQLS) and a bowel habit diary completed before randomization, during the study period and after 3 months of follow-up with one preferred setting.

Results

Fifteen patients were analysed. With one preferred setting, three of four subdomains in the FIQLS improved significantly. The mean(s.d.) total number of incontinence episodes dropped from 11·7(10·8) to 4·8(4·5) per 3 weeks (P = 0·011) and improvements were maintained after 3 months of follow-up. Optimal pacemaker settings were individual, but a trend towards highest patient satisfaction and improved treatment outcome was evident for high-frequency stimulation (31 Hz/210 µs), which was preferred by eight of the 15 patients.

Conclusion

Patients experiencing loss of efficacy can experience improvement if alternative pacemaker settings are tested. High-frequency stimulation (31 Hz/210 µs) was preferred by more than half of the patients, and improved treatment outcome was sustained at 3 months. Registration number: NCT01254695 (http://www.clinicaltrials.gov).

Prospective randomized double-blind study of temporary sacral nerve stimulation in patients with rectal evacuatory dysfunction and rectal hyposensitivity

OBJECTIVE

Prospective randomized double-blind placebo-controlled crossover trial of 14 female patients (median age 52 [30-69] years) with proctographically defined evacuatory dysfunction (ED) and demonstrable rectal hyposensitivity (elevated thresholds to balloon distension in comparison with age- and sex-matched controls).

BACKGROUND

Sacral nerve stimulation (SNS) is an evolving treatment for constipation. However, variable outcomes might be improved by better patient selection. Evidence that the effect of SNS may be mediated by modulation of afferent signaling promotes a role in patients with ED associated with rectal hyposensation.

METHODS

SNS was performed by the standard 2-stage technique (temporary then permanent implantation). During a 4-week period of temporary stimulation, patients were randomized ON-OFF/OFF-ON for two 2-week periods. Before insertion (PRE), and during each crossover period, primary (rectal sensory thresholds) and secondary (bowel diaries, constipation, and GIQoL [gastrointestinal quality of life] scores) outcome variables were blindly assessed.

RESULTS

Thirteen patients completed the trial. Following stimulation, defecatory desire volumes to rectal balloon distension were normalized in 10 of 13 patients (PRE: mean 277 mL [234-320] vs ON: 163 mL [133-193] vs OFF: 220 mL [183-257 mL]; P = 0.006) and maximum tolerable volume in 9 of 13 (PRE: mean 350 mL [323-377] vs ON: 262 mL [219-305] vs OFF: 298 mL [256-340 mL]; P = 0.012). There was a significant increase in the percentage of successful bowel movements (PRE: median 43% [0-100] vs ON: 89% [11-100] vs OFF: 83% [11-100]; P = 0.007) and Wexner constipation scores improved (PRE: median 19 [9-26] vs ON: 10 [6-27] vs OFF: 13 [5-29]; P = 0.01). There were no significant changes in disease-specific or generic quality of life measures. Eleven patients progressed to permanent stimulation (9/11 success at 19 months).

CONCLUSIONS

Most patients with chronic constipation secondary to ED with rectal hyposensitivity responded to temporary SNS. The physiological results presented support a mechanistic role for rectal afferent modulation.

Sacral nerve stimulation for fecal incontinence related to external sphincter atrophy

BACKGROUND

Atrophy of the external anal sphincter, a pathologic muscle volume anomaly associated with fecal incontinence, has been shown to be a negative predictor of the outcome of surgery for defects of the external anal sphincter. It is unclear whether external anal sphincter atrophy also affects the outcome of sacral nerve stimulation for fecal incontinence.

OBJECTIVE

Our aim was to assess the effectiveness of sacral nerve stimulation in patients with fecal incontinence and external anal sphincter atrophy and to determine whether severity of atrophy and concomitant presence of a sphincter defect are negative predictors of outcome.

DESIGN

This was a prospective observational study of treatment outcome.

SETTING

The study was conducted from November 2004 through November 2010 at a regional hospital in Italy.

PATIENTS

Consecutive patients with fecal incontinence and external anal sphincter atrophy were included. By means of MRI, patients were determined to have either moderate (<50%) or severe (≥ 50%) thinning of and/or replacement of sphincter muscle by fat. The concomitant presence of defects of the external anal sphincter was also detected by MRI.

INTERVENTION

All patients underwent sacral nerve stimulation through a staged implantation procedure.

MAIN OUTCOME MEASURES

The main outcome measures were improvement in the Cleveland Clinic Florida Fecal Incontinence Scale (Wexner score), number of episodes of incontinence per week, and the Fecal Incontinence Quality of Life Scale.

RESULTS

A total of 28 patients underwent definitive implantation of the sacral nerve stimulation device. Wexner scores decreased from a median of 16 (range, 10-20) at baseline to 3 (range, 0-8) at 6-month follow-up (p < 0.001). Weekly incontinence episodes decreased from a mean (SD) of 14.7 (12.5) to 0.40 (0.82); p < 0.001. Improvement was significantly related to severity of fecal incontinence (r = 0.86; p < 0.001). Overall quality-of-life scores improved from a mean of 1.8 (0.6) to 3.8 (0.4);p < 0.001. Sacral nerve stimulation was effective in both moderate (n = 16) and severe (n = 12) atrophy and in patients with (n = 8) or without (n = 20) external anal sphincter defects.

LIMITATIONS

The study was limited by its observational nature and relatively small sample size.

CONCLUSIONS

Sacral nerve stimulation can be effective in restoring continence and improving quality of life in patients with fecal incontinence related to atrophy of the external anal sphincter, regardless of the severity of atrophy. Moreover, the presence of EAS atrophy does not influence the success of the outcome of SNS in patients with a sphincter defect. These findings are consistent with the hypothesis that the effects of SNS are not achieved solely by its action on the anal sphincter complex.

Sacral nerve stimulation enhances epithelial barrier of the rectum: results from a porcine model

BACKGROUND

The mechanism of action of sacral nerve stimulation (SNS) remains largely elusive. The aims of this study were to develop a clinically relevant animal model for percutaneous SNS and to describe its effect on the epithelial barrier of the rectum.

METHODS

Under general anesthesia and after percutaneous electrode placement for S3 nerve root stimulation, six pigs underwent unilateral stimulation and six bilateral stimulation. Animals were stimulated for 3 h using an external pulse generator (1-2.5 V; 14 Hz; 210 μs). Six animals underwent electrode implantation without stimulation and served as controls. Full-thickness rectal biopsies were performed prior to and after stimulation. Paracellular permeability was evaluated by measuring sulfonic acid flux across the rectal mucosa in Ussing chambers. Histological assessment of mucosal thickness, epithelial desquamation, and mucus expression were performed.

KEY RESULTS

Percutaneous stimulation resulted in successful anal contractions whose amplitude and uniformity was enhanced following bilateral compared with unilateral stimulation. In controls, paracellular permeability significantly increased during the stimulation period whereas it remained unchanged following unilateral stimulation. In contrast, permeability was significantly reduced by bilateral stimulation. This effect was associated with a concomitant reduction in mucosal thickness and a trend toward increased amount of mucus on surface epithelium compared with controls.

CONCLUSIONS & INFERENCES

The development of a porcine model of percutaneous SNS revealed the ability of neuromodulation to reinforce rectal epithelial barrier. Furthermore, our results suggest that SNS could be used for treatment of gastrointestinal pathologies with reduced rectal mucosal barrier functions.