A Historical Perspective on Sacral Nerve Stimulation (SNS) for Bowel Dysfunction

Prevention of obstetric trauma from damage to the pelvic floor is not always possible and sacral nerve stimulation (SNS) may be necessary later in life. Sacral nerve stimulation has been a promising innovation in the management of moderate to severe faecal incontinence and following sphincter repair failure. Although the indication spectrum for SNS is expanding, the success of neuromodulation for constipation is limited. Adverse events of SNS requiring re-intervention are not common but a long-term successful outcome may depend on interventions for maintenance of the device.

Neuro-Immune Modulation Effects of Sacral Nerve Stimulation for Visceral Hypersensitivity in Rats

Background: Visceral hypersensitivity (VH) is one of the underlying pathophysiologies of irritable bowel syndrome. Mast cell overactivation has been found to be one of the main causes of VH. We investigated the effects and mechanisms of actions of sacral nerve stimulation (SNS) on visceral pain in a rodent model of VH.Methods: The VH was established by an intrarectal infusion of AA in 10-day-old pups. Rats were chronically implanted with electrodes for SNS and recording electromyogram (EMG) and electrocardiogram. The acute study was performed in 2-randomized sessions with SNS (14 Hz, 330 μs, 40% motor threshold or MT, 30 min) or sham-SNS. Later on, rats were randomized into SNS/sham-SNS groups and a chronic study was performed with 2 h-daily SNS or sham-SNS for 21 days. Visceromotor reflexes were assessed by abdominal EMG and withdrawal reflex (AWR). Colon tissues were collected to study colonic acetylcholine (ACh), the enteric neurons (ChAT, nNOS, and PGP9.5), mast cells activity [Tryptase, prostaglandins E2 (PGE2), and cyclooxygenases-2 (COX2)] and pain markers [nerve growth factor (NGF) and Sub-P].Key Results: Sacral nerve stimulation significantly improved visceromotor reflexes assessed by the EMG and AWR, compared with sham-SNS. SNS normalized the protein expressions of ChAT and nNOS and regulated mast cells activity by downregulating Tryptase, COX2, and PGE2. Neonatal AA administration upregulated NGF and Sub-P; chronic SNS significantly decreased these pain biomarkers. Concurrently, chronic SNS increased ACh in colon tissues and vagal efferent activity.Conclusions: Sacral nerve stimulation reduces VH in rats and this ameliorating effect might be attributed to the suppression of mast cell overactivation in the colon tissue via the modulation of autonomic nervous system functions.

Sacral nerve stimulation in patients with ileal pouch-anal anastomosis

Purpose Functional results after proctocolectomy and ileal pouch-anal anastomosis (IPAA) are generally good. However, some patients suffer from high stool frequency or fecal incontinence. Sacral nerve stimulation (SNS) may represent a therapeutic alternative in these patients, but little is known about indication and results. The aim of this study was to evaluate incontinence after IPAA and demonstrate SNS feasibility in these patients. Methods This retrospective study includes patients who received a SNS between 1993 and 2020 for increased stool frequency or fecal incontinence after proctocolectomy with IPAA for ulcerative colitis. Proctocolectomy was performed in a two- or three-step approach with ileostomy closure as the last step. Demographic, follow-up data and functional results were obtained from the hospital database. Results SNS was performed in 23 patients. Median follow-up time after SNS was 6.5 years (min. 4.2–max. 8.8). Two patients were lost to follow-up. The median time from ileostomy closure to SNS implantation was 6 years (min. 0.5–max. 14.5). Continence after SNS improved in 16 patients (69%) with a median St. Marks score for anal incontinence of 19 (min. 4–max. 22) before SNS compared to 4 (0–10) after SNS placement (p = 0.012). In seven patients, SNS therapy was not successful. Conclusion SNS implantation improves symptoms in over two-thirds of patients suffering from high stool frequency or fecal incontinence after proctocolectomy with IPAA. Awareness of the beneficial effects of SNS should be increased in physicians involved in the management of these patients.

Sacral Nerve Stimulation Lead Migration through the Sciatic Foramen, Successfully Repositioned

Introduction: SNS (Sacral Nerve Stimulation) has become an established minimally invasive procedure for urinary and faecal incontinence. Minor complications related to the procedure are common; include pain, infection or migration. We present a case of a tined lead migration through the sciatic foramen. Case Report: A 72-year-old woman with faecal incontinence, who did not respond to dietary of medical treatment, underwent a sacral nerve stimulation test. Under fluoroscopic vision a tined lead was placed in S3 foramen, with an adequate motor and sensory response. In the 7th postoperative day, she reported no improvement and she referred sensory response in the thigh and leg. Radiography showed migration of the electrode through the sciatic foramen. The repositioning of the same electrode was possible with a gentle traction of the lead. Correct placement of the lead was confirmed radiologically, and the patient showed motor and sensory response in the anal area. The patient improved Wexner score from 18/20 to 4/20. Conclusion: Migration of the tined lead should be considered if loss of response in found. Repositioning of the same lead is possible in selected patients, without the need of removal of the device.

Sacral nerve stimulation versus the magnetic sphincter augmentation device for adult faecal incontinence: the SaFaRI RCT

Background Preliminary studies using the FENIX™ (Torax Medical, Minneapolis, MN, USA) magnetic sphincter augmentation device suggest that it is safe to use for the treatment of adult faecal incontinence, but efficacy data are limited. Objective To compare FENIX with sacral nerve stimulation for the treatment of adult faecal incontinence in terms of safety, efficacy, quality of life and cost-effectiveness. Design, setting and participants Multicentre, parallel-group, unblinded, randomised trial comparing FENIX with sacral nerve stimulation in participants suffering moderate to severe faecal incontinence. Interventions Participants were randomised on an equal basis to either sacral nerve stimulation or FENIX. Follow-up occurred 2 weeks postoperatively and at 6, 12 and 18 months post randomisation. Main outcome and measure The primary outcome was success, defined as device in use and ≥ 50% improvement in Cleveland Clinic Incontinence Score at 18 months post randomisation. Secondary outcomes included complication rates, quality of life and cost-effectiveness. Between 30 October 2014 and 23 March 2017, 99 participants were randomised across 18 NHS sites (50 participants to FENIX vs. 49 participants to sacral nerve stimulation). The median time from randomisation to FENIX implantation was 57.0 days (range 4.0–416.0 days), and the median time from randomisation to permanent sacral nerve stimulation was 371.0 days (range 86.0–918.0 days). A total of 45 out of 50 participants underwent FENIX implantation and 29 out of 49 participants continued to permanent sacral nerve stimulation. The following results are reported, excluding participants for whom the corresponding outcome was not evaluable. Overall, there was success for 10 out of 80 (12.5%) participants, with no statistically significant difference between the two groups [FENIX 6/41 (14.6%) participants vs. sacral nerve stimulation 4/39 (10.3%) participants]. At least one postoperative complication was experienced by 33 out of 45 (73.3%) participants in the FENIX group and 9 out of 40 (22.5%) participants in the sacral nerve stimulation group. A total of 15 out of 50 (30%) participants in the FENIX group ultimately had to have their device explanted. Slightly higher costs and quality-adjusted life-years (incremental = £305.50 and 0.005, respectively) were observed in the FENIX group than in the sacral nerve stimulation group. This was reversed over the lifetime horizon (incremental = –£1306 and –0.23 for costs and quality-adjusted life-years, respectively), when sacral nerve stimulation was the optimal option (net monetary benefit = –£3283), with only a 45% chance of FENIX being cost-effective. Limitations The SaFaRI study was terminated in 2017, having recruited 99 participants of the target sample size of 350 participants. The study is, therefore, substantially underpowered to detect differences between the treatment groups, with significant uncertainty in the cost-effectiveness analysis. Conclusions The SaFaRI study revealed inefficiencies in the treatment pathways for faecal incontinence, particularly for sacral nerve stimulation. The success of both FENIX and sacral nerve stimulation was much lower than previously reported, with high postoperative morbidity in the FENIX group. Future work Further research is needed to clarify the treatment pathways for sacral nerve stimulation and to determine its true clinical and cost-effectiveness. Trial registration Current Controlled Trials ISRCTN16077538. Funding This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 25, No. 18. See the NIHR Journals Library website for further project information.