The influence of sacral nerve stimulation on gastrointestinal motor function in patients with fecal incontinence

Regulation of enteric nervous system via sacral nerve stimulation in opioid-induced constipated rats

Objectives

Sacral nerve stimulation (SNS) has been employed for treating constipation. However, its mechanisms involving enteric nervous system (ENS) and motility are largely unknown. In this study, we investigated the possible ENS involvement of SNS in treating Loperamide-induced constipation in rats.

Methods

Experiment-1 was designed to study the effects of acute SNS on whole colon transit time (CTT). In experiment-2, we induced constipation by Loperamide and then applied daily SNS or sham-SNS for 1 week. Choline acetyltransferase (ChAT), nitric oxide synthase (nNOS), and PGP9.5 in colon tissue were examined at the end of the study. Moreover, survival factors such as phosphorylated AKT (p-AKT) and Glial cell-derived neurotrophic factor (GDNF) were measures by immunohistochemistry (IHC) and western blot (WB).

Key results

(1) SNS with one set of parameters shortened CTT starting at 90 min after phenol red administration (p < 0.05). (2) While Loperamide induced slow transit constipation with a significant reduction in fecal pellet number and feces wet weight, daily SNS for a week resolved constipation. (3) Moreover, SNS was able to shorten whole gut transit time comparing to sham-SNS (p = 0.01). (4) Loperamide reduced the number of PGP9.5 and ChAT positive cells, and downregulated ChAT protein expression and upregulated nNOS protein expression, whereas these detrimental effects were significantly reversed by SNS. (5) Furthermore, SNS increased expressions of both GDNF and p-AKT in colon tissue. (6) Vagal activity was reduced following Loperamide (p < 0.01); yet SNS normalized vagal activity.

Conclusion

SNS with appropriate parameters improves opioid-induced constipation and reversed the detrimental effects of Loperamide on enteric neurons possibly via the GDNF-PI3K/Akt pathway.GRAPHICAL ABSTRACT.

Sacral nerve stimulation increases gastric accommodation in rats: a spinal afferent and vagal efferent pathway

Impaired gastric accommodation (GA) has been frequently reported in various gastrointestinal diseases. No standard treatment strategy is available for treating impaired GA. We explored the possible effect of sacral nerve stimulation (SNS) on GA and discovered a spinal afferent and vagal efferent mechanism in rats. Sprague-Dawley rats (450-500 g) with a chronically implanted gastric cannula and ECG electrodes were studied in a series of sessions to study: 1) the effects of SNS with different parameters on gastric tone, compliance, and accommodation using a barostat device; two sets of parameters were tested as follows: parameter 1) 5 Hz, 500 µs, 10 s on 90 s off; 90% motor threshold and parameter 2) same as parameter 1 but 25 Hz; 2) the involvement of spinal afferent pathway via detecting c-fos immunoreactive (IR) cells in the nucleus of the solitary tract (NTS) of the brain; 3) the involvement of vagal efferent activity via the spectral analysis of heart rate variability derived from the ECG; and 4) the nitrergic mechanism, N^ω-nitro-l-arginine methyl ester (l-NAME), a nitric oxide synthase (NOS) inhibitor, was given before SNS at 5 Hz. Compared with sham-SNS: 1) SNS at 5 Hz inhibited gastric tone and increased gastric compliance and GA. No difference was noted between the stimulation frequencies of 5 and 25 Hz. 2) SNS increased the expression of c-fos in the NTS. 3) SNS increased cardiac vagal efferent activity and decreased the sympathovagal ratio. 4) l-NAME blocked the relaxation effect of SNS. In conclusion, SNS with certain parameters relaxes gastric fundus and improves gastric accommodation mediated via a spinal afferent and vagal efferent pathway.NEW & NOTEWORTHY Currently, there is no adequate medical therapy for impaired gastric accommodation, since medications that relax the fundus often impair antral peristalsis and thus further delay gastric emptying that is commonly seen in patients with functional dyspepsia or gastroparesis. The advantage of the potential sacral nerve stimulation therapy is that it improves gastric accommodation by enhancing vagal activity, and the enhanced vagal activity would lead to enhanced antral peristalsis rather than inhibiting it.

Sacral nerve stimulation with appropriate parameters improves constipation in rats by enhancing colon motility mediated via the autonomic-cholinergic mechanisms

Although sacral nerve stimulation (SNS) has been applied for treating constipation, its parameters were adopted from SNS for fecal incontinence, its effects are limited, and mechanisms are largely unknown. We investigated the effects and mechanism of SNS with appropriate parameters on constipation in rats treated with loperamide. First, using rectal compliance as an outcome measure, an experiment was performed to derive effective SNS parameters. Then, a 7-day SNS was performed in rats with constipation induced by loperamide. Autonomic functions were assessed by spectral analysis of heart rate variability (HRV) derived from an electrocardiogram. Serum levels of pancreatic polypeptide (PP), norepinephrine (NE), and acetylcholine (ACh) in colon were assessed. 1) Acute SNS at 5 Hz, 100 µs was found effective in enhancing rectal compliance and accelerating distal colon transit (P < 0.05 vs. sham SNS). 2) The 7-day SNS normalized loperamide-induced constipation, assessed by the number, weight, and water content of fecal pellets, and accelerated the distal colon transit (29.4 ± 3.7 min with sham SNS vs. 16.4 ± 5.3 min with SNS but not gastric emptying or intestinal transit. 3) SNS significantly increased vagal activity (P = 0.035) and decreased sympathetic activity (P = 0.012), assessed by spectral analysis of HRV as well as by the serum PP. 4) SNS increased ACh in the colon tissue; atropine blocked the accelerative effect of SNS on distal colon transit. We concluded that SNS with appropriate parameters improves constipation induced by loperamide by accelerating distal colon motility, mediated via the autonomic-cholinergic function.NEW & NOTEWORTHY Although sacral nerve stimulation (SNS) has been applied for treating constipation, its parameters were adopted from SNS for fecal incontinence, effects are limited, and mechanisms are largely unknown. This paper shows that SNS with appropriate parameters improves constipation induced by loperamide by accelerating distal colon motility mediated via the autonomic-cholinergic function.

Systematic review of the impact of sacral neuromodulation on clinical symptoms and gastrointestinal physiology

Background

Sacral neuromodulation (SNM) has emerged as a treatment option for faecal incontinence (FI). However, its objective effect on symptoms and anorectal function is inconsistently described. This study aimed to systematically review the impact of SNM on clinical symptoms and gastrointestinal physiology in patients with FI, including factors that may predict treatment outcome.

Methods

An electronic search of MEDLINE (1946–2014)/EMBASE database was performed in accordance with PRISMA guidelines. Articles that reported the relevant outcome measures following SNM were included. Clinical outcomes evaluated included: frequency of FI episodes, FI severity score and success rates. Its impact on anorectal and gastrointestinal physiology was also evaluated.

Results

Of 554 citations identified, data were extracted from 81 eligible studies. Meta‐analysis of the data was precluded due to lack of a comparison group in most studies. After permanent SNM, ‘perfect’ continence was noted in 13–88% of patients. Most studies reported a reduction in weekly FI episodes (median difference of the mean −7.0 (range: −24.8 to −2.7)) and Wexner scores (median difference of the mean −9 (−14.9 to −6)). A trend towards improved resting and squeeze anal pressures and a reduction in rectal sensory volumes were noted. Studies failed to identify any consistent impact on other physiological parameters or clinicophysiological factors associated with success.

Conclusion

SNM improves clinical symptoms and reduces number of incontinence episodes and severity scores in patients with FI, in part by improving anorectal physiological function. However, intervention studies with standardized outcome measures and physiological techniques are required to robustly assess the physiological impact of SNM.

A prospective trial of temporary sacral nerve stimulation for constipation associated with neurological disease

AIM

This study assessed the effectiveness of temporary sacral nerve stimulation (SNS) in patients with constipation associated with neurological disease using an off-on-off design, and evaluated the long-term response in patients undergoing permanent SNS.

METHOD

Patients with chronic constipation associated with neurological disease receiving specialist clinic care at the University Hospital North Durham over a 2-year period were recruited to a trial of SNS. Recordings of bowel function were made for 6 weeks (baseline) and a temporary electrode was then inserted and recordings were made for the next 3 weeks (stimulation). The electrodes were then removed and assessment was continued for a further 3 weeks (posttreatment). Patient-completed questionnaires were used to determine the severity of constipation (Global Assessment of Symptoms, Constipation, GA Constipation), symptoms (Patient Assessment of Constipation Symptoms score, PAC-SYM) and quality-of-life (Patient Assessment of Constipation-Quality Of Life score, PAC-QOL; European Quality of Life-Five-Domain score; European Quality of Life-Visual Analogue Score). Information was obtained on bowel function and medication. Physiological data were also available for transit and laser Doppler flow cytometry to measure mucosal blood flow.

RESULTS

Twenty-two patients were recruited, of whom 18 completed the trial. GA Constipation reduced significantly during temporary SNS: -1.09 (95% CI -1.59 to -0.59; P = 0.0003). PAC-SYM and PAC-QOL scores showed similar improvements. There was also a significant fall in the time spent in the toilet (P = 0.04) and a decrease in laxative use (P = 0.03). Twelve (67%) patients responded to temporary SNS and received a permanent implant with long-term success in 50%.

CONCLUSION

Sacral nerve stimulation can be effective in treating some patients with refractory severe neuroconstipation. A response to temporary SNS may predict long-term benefit in only half the patients undergoing permanent SNS.

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.

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).

Colonic electrical stimulation for the treatment of slow-transit constipation: a preliminary pilot study

BACKGROUND

Electrical stimulation of the gastrointestinal tract is an attractive concept. In this article we report on a procedure for electrical colonic pacing due to intramuscular electrode placement for slow-transit constipation and some preliminary results.

METHODS

From January 2011 to December 2012, all consecutive patients affected by constipation and evaluated in our Pelvic Floor Center were prospectively assessed. Patients who underwent colonic electrical stimulation were evaluated for the present study.

RESULTS

In the study period, 256 patients were evaluated for constipation; 58% were identified as having obstructed defecation syndrome, 27.3% with irritable bowel syndrome or mixed forms, 4% with pelvic floor dyssynergia, and 10.5% (27 patients) as having slow-transit constipation. After failure of all the maximal conventional therapies, two patients, candidates for colectomy, agreed to undergo colonic electrical stimulation before a resective treatment. Both patients were females, aged 34 and 29 years, and were suffering from severe constipation since childhood. The follow-up was 19 and 6 months. The number of bowel movements per week increased from 0.3 to 3.5 in the first patient and from 0.5 to 2.5 in the second patient. Both patients no longer needed laxatives, enemas, or any other treatment. The hospital stay was 4 days, the mean operative time was 120 min, and no complications were reported.

CONCLUSIONS

Colonic pacing seems to be feasible and shows positive results. Further studies are required with a larger number of patients and a longer follow-up period to confirm the role of this promising treatment for slow-transit constipation.

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.