Rapid rate magnetic stimulation of human sacral nerve roots alters excitability within the cortico-anal pathway

[Sacral magnetic stimulation in overactive bladder syndrome: comparative analysis of protocols with a frequency of 1 and 5 Hz]

Peripheral magnetic stimulation (pMS) has shown its effectiveness in the treatment of lower urinary tract symptoms, such as symptoms of an overactive bladder (OAB). The perineal region (pelvic floor) and the sacral roots area (projection S3 of the root) are used as the locus of stimulation. The published literature presents protocols with different parameters of stimulation, while each of them reliably demonstrates clinical efficacy, however, no comparative studies have been found to select priority stimulation modes when analyzing available sources.

OBJECTIVE

To compare the efficacy and safety of different frequency - 1 and 5 Hz - modes of sacral MS in patients with symptoms of OAB.

MATERIAL AND METHODS

A single blind prospective randomized comparative clinical study included 59 patients with OAB symptoms. The patients were divided by simple randomization into the group 1 (n=30), which received MS 3 times a week for 5 weeks with a frequency of 1 Hz per sacral root area (S2-S4), and the group 2 (n=29), in which stimulation was performed at a frequency of 5 Hz, while the remaining parameters and duration of therapy were identical to group 1.

RESULTS

Sacral pMS with different frequency modes (1 and 5 Hz) is reliably equally effective against the clinical symptoms of OAB, which is confirmed by the absence of significant intergroup differences. In patients receiving MS with a frequency of 5 Hz, there was a more pronounced increase in maximum cystometric capacity, normalization of the maximum and average urine flow velocity and regression of the residual urine volume (p<0.001, p=0.007, p=0.011 and p=0.012 compared with group 1). The greatest difference in indicators was observed in the increase in the maximum cystometric capacity - +31±25 ml at MS with a frequency of 1 Hz and +109±96 ml at MS with a frequency of 5 Hz (p<0.001). MS is a safe procedure and is well tolerated by patients.

CONCLUSION

pMS when exposed to the area of S2-S4 roots for 20 minutes 3 times a week with a course for 5 weeks is reliably effective against the clinical symptoms of OAB at different frequency modes (1 and 5 Hz). At the same time, MS with a frequency of 5 Hz may have an advantage over stimulation of 1 Hz in terms of its effect on urodynamic parameters (maximum cystometric capacity, peak and average urine flow velocity and residual urine volume), which may be associated with a large inhibitory effect on detrusor.

Efficacy of the magnetic stimulation of sacral nerve roots combined with Tui-na on neurogenic bladder after spinal cord injury: preliminary short-term results

OBJECTIVE

Neurogenic bladder (NGB) is a serious complication after spinal cord injury (SCI), a destructive neurological disease. This study focused on exploring the efficacy of the magnetic stimulation of sacral nerve roots combined with Tui-na in treating NGB after SCI.

METHODS

One hundred patients with NGB after SCI were studied, and intermittent clean catheterization was performed with a water intake program, and patients were grouped into four groups by the random number table method: general treatment group, Tui-na group, magnetic stimulation group, and combined treatment group. A series of relevant factors (voiding diary, urodynamics, and quality of life scores) and clinical efficacy of patients in the four groups before and after treatment were observed.

RESULTS

The magnetic stimulation of sacral nerve roots alone, Tui-na alone, and the combination of both were all effective in improving bladder function and quality of life in patients with NGB after SCI, including improvements in voiding frequency, single urine output, maximum urine output, residual urine output, bladder volume and quality of life scores in patients with NGB after SCI. The efficacy of the magnetic stimulation of sacral nerve roots combined with Tui-na was better than that of the magnetic stimulation of sacral nerve roots alone and the Tui-na alone.

CONCLUSION

This research demonstrates that the magnetic stimulation of sacral nerve roots combined with Tui-na treatment could effectively improve the urinary system and the quality of life of patients with NGB after SCI, which is worthy of clinical promotion and application.

Effects of Translumbosacral Neuromodulation Therapy on Gut and Brain Interactions and Anorectal Neuropathy in Fecal Incontinence: A Randomized Study

OBJECTIVES

Translumbosacral neuromodulation therapy (TNT) improves symptoms of fecal incontinence (FI), but its mechanism of action is unknown. We tested the hypothesis that TNT at one or more frequency will significantly improve underlying pathophysiology of FI through modulation of ascending and/or descending signaling pathways in the gut and brain axis and anorectal sensorimotor function.

MATERIALS AND METHODS

We assessed afferent anorectal-cortical evoked potentials (CEP) following electrical stimulation of anorectum, efferent cortico-anorectal and lumbo-anorectal and sacro-anorectal motor evoked potentials (MEP) after transcranial and lumbosacral magnetic stimulations, and anorectal manometry before and after six weekly TNT sessions in FI subjects, randomized to 1, 5, or 15 Hz repetitive magnetic stimulations. Neurophysiology, anorectal sensorimotor function, and symptoms were compared to examine mechanistic effects. Co-primary measures were ano-cortical CEPs, cortico-anal MEPs, and lumbosacral-anal MEPs. Baseline and post-treatment data were compared with Wilcoxon signed-rank test and changes between the three frequencies with one-way ANOVA.

RESULTS

Thirty-three FI patients participated. After TNT, the afferent anal CEP latencies significantly decreased in the 1 Hz group compared to baseline (p = 0.0029) and 5 Hz or 15 Hz groups (p = 0.032). Cortico-anal MEPs were unchanged in all three groups. Bilateral lumbo-anal and sacro-anal MEP latencies significantly decreased with 1 Hz, lumbo-anal with 15 Hz, and sacro-anal with 5 Hz compared to baseline but without group differences. The 1 Hz group showed significant increase in anal squeeze sphincter pressure (p < 0.005) and maximum tolerable volume (p < 0.019) and demonstrated higher FI responder rate (p < 0.04) compared to the other two groups. The MEP responders were significantly correlated with FI responders (p = 0.006) in 1 Hz group.

CONCLUSIONS

TNT significantly improves afferent ano-cortical signaling, efferent lumbo-anal and sacro-anal neuropathy and anorectal sensorimotor function. These neurobiologic effects were most prominent with 1 Hz frequency. TNT improves FI by modifying the underlying pathophysiology possibly through neuromodulation.

Translumbosacral Neuromodulation Therapy for Fecal Incontinence: A Randomized Frequency Response Trial

INTRODUCTION

Treatments for fecal incontinence (FI) remain unsatisfactory because they do not remedy the underlying multifactorial dysfunction(s) including anorectal neuropathy. The aim of this study was to investigate the optimal dose frequency, clinical effects, and safety of a novel treatment, translumbosacral neuromodulation therapy (TNT), aimed at improving neuropathy.

METHODS

Patients with FI were randomized to receive 6 sessions of weekly TNT treatments consisting of 600 repetitive magnetic stimulations over each of 2 lumbar and 2 sacral sites with either 1, 5, or 15 Hz frequency. Stool diaries, FI severity indices, anorectal neurophysiology and sensorimotor function, and quality of life were compared. Primary outcome measure was the change in FI episodes/week. Responders were patients with ≥50% decrease in weekly FI episodes.

RESULTS

Thirty-three patients with FI participated. FI episodes decreased significantly (∆ ±95% confidence interval, 4.2 ± 2.8 (1 Hz); 2 ± 1.7 (5 Hz); 3.4 ± 2.5 (15 Hz); P < 0.02) in all 3 groups when compared with baseline. The 1 Hz group showed a significantly higher (P = 0.04) responder rate (91 ± 9.1%) when compared with the 5 Hz group (36 ± 18.2%) or 15 Hz (55 ± 18.2%); no difference was found between the 5 and 15 Hz groups (P = 0.667). Anal neuropathy, squeeze pressure, and rectal capacity improved significantly only in the 1 Hz (P < 0.05) group compared with baseline, but not in other groups. Quality of life domains improved significantly (P < 0.05) with 1 and 5 Hz groups. No device-related serious adverse events were noted.

DISCUSSION

TNT significantly improves FI symptoms in the short term, and the 1 Hz frequency was overall better than 5 and 15 Hz. Both anorectal neuropathy and physiology significantly improved, demonstrating mechanistic improvement. TNT is a promising, novel, safe, efficacious, and noninvasive treatment for FI (see Visual Abstract, Supplementary Digital Content 3, http://links.lww.com/AJG/B598).

Translumbosacral Neuromodulation Therapy Is a Promising Option for Fecal Incontinence

ABSTRACT

Fecal incontinence is a common symptom that can significantly impair quality of life. The treatment options range from conservative measures (e.g., Kegel exercises, pelvic floor biofeedback therapy, fiber supplementation, or medications) to noninvasive nerve stimulation (e.g., posterior tibial nerve stimulation and transcutaneous tibial nerve stimulation), implanted neurostimulation (i.e., sacral nerve stimulation), perianal injection of dextranomer, and anal sphincteroplasty. In this issue of the journal, a promising, uncontrolled study suggests that noninvasive, repetitive magnetic stimulation of the lumbosacral nerves significantly improved symptoms, increased anal squeeze pressure, and increased rectal compliance in patients with fecal continence. Sham-controlled studies are necessary to confirm these findings.

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.

Anorectal angle at rest predicting successful sacral nerve stimulation in idiopathic fecal incontinence-a cohort analysis

PURPOSE

Sacral nerve stimulation is an effective treatment for patients suffering from fecal incontinence. However, less is known about predictors of success before stimulation. The purpose of this study was to identify predictors of successful sacral nerve stimulation in patients with idiopathic fecal incontinence.

METHODS

Consecutive female patients, receiving peripheral nerve evaluation and sacral nerve stimulation between September 2008 and October 2014, suffering from idiopathic fecal incontinence were included in this study. Preoperative patient's characteristics, anal manometry, and defecography results were collected prospectively and investigated by retrospective analysis. Main outcome measures were independent predictors of treatment success after sacral nerve stimulation.

RESULTS

From, all in all, 54 patients suffering from idiopathic fecal incontinence receiving peripheral nerve evaluation, favorable outcome was achieved in 23 of 30 patients after sacral nerve stimulation (per protocol 76.7%; intention to treat 42.6%). From all analyzed characteristics, wide anorectal angle at rest in preoperative defecography was the only independent predictor of favorable outcome in multivariate analysis (favorable 134.1 ± 13.9° versus unfavorable 118.6 ± 17.1°).

CONCLUSIONS

Anorectal angle at rest in preoperative defecography might present a predictor of outcome after sacral nerve stimulation in patients with idiopathic fecal incontinence.

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.

Increase of n-NOS and i-NOS in Rat Colon After Sacral Neuromodulation

OBJECTIVE

Sacral neuromodulation (SNM) is proposed to treat different anorectal dysfunctions but its mechanism of action is not yet known. Our previous study demonstrated how SNM can significantly increase neuronal nitric oxide synthase NOS (n-NOS) and inducible NOS (i-NOS) expression in the anus and rectum of rats. There are no reports regarding the relation between SNM and NOS in colonic cells: our aim was to assess NOS expression in colonic rat model after SNM.

MATERIALS AND METHODS

Twenty-six female Sprangue-Dawley rats were considered: group I, normal control rats; group II, sham treatment rats, in whom electrodes for electrical stimulation were placed in S1 foramen bilaterally and left in place, without performing neuromodulation; group III, rats in whom SNM was performed. After 14 days, the rats were sacrificed and we evaluated n-NOS and i-NOS in colonic specimens by immunohistochemistry and Western Blot analysis.

RESULTS

Western Blot analysis showed that levels of n-NOS and i-NOS were higher in colon of the III group rats respect to the others; in particular, immunohistochemistry revealed that, after neuromodulation, n-NOS expression in the muscle cells and i-NOS expression in glandular epithelium and nervous cells were highly represented (p < 0.05).

CONCLUSION

Our study showed that in colon, SNM is able to influence NO synthesis, activating n-NOS expression in muscle cells and i-NOS expression in glandular epithelium and nervous cells. Our study showed a complex colonic response to SNM. This experimental model could be applied to better understand the mechanism of action of SNM in bowel dysfunction.

A double-blind randomized clinical trial on the efficacy of magnetic sacral root stimulation for the treatment of Monosymptomatic Nocturnal Enuresis

Purpose: Purpose of this study was to evaluate the long term efficacy of repetitive sacral root magnetic stimulation (rSMS) in patients with monosymptomatic nocturnal enuresis (MNE).

Methods: Forty four patients were randomized to receive either sham or real repetitive sacral root magnetic stimulation (rSMS; 15 Hz with a total of 1500 pulses/session) for 10 sessions. Evaluation was performed before starting treatment, immediately after the 5th and 10th treatment session, and 1 month later, using frequency of enuresis/week, visual analogue scale (VAS) and quality of life as outcome measures. Resting and active motor thresholds of gastrocnemius muscles were measured before and after the end of sessions.

Results: Both treatment and control groups were comparable for baseline measures of frequency of enuresis, and VAS. The mean number of wet nights/week was significantly reduced in patients who received real rSMS. This improvement was maintained 1 month after the end of treatment. Patients receiving real-rSMS also reported an improvement in VAS ratings and quality of life. A significant reduction of resting motor threshold was recorded after rSMS in the real group while no such changes were observed in the sham group.

Conclusion: These findings suggest that rSMS has potential as an adjuvant treatment for MNE and deserves further study.

Modulation of human visceral sensitivity by noninvasive magnetoelectrical neural stimulation in health and irritable bowel syndrome

Visceral pain is a particularly difficult symptom to manage in patients with irritable bowel syndrome (IBS). Our aim was to examine whether noninvasive neurostimulation applied to the motor cortex or lumbosacral region can modulate human visceral sensation. Sixteen healthy adult volunteers and 10 patients with IBS were evaluated. Single-pulse lumbosacral magnetic stimulation (LSMS) or transcranial magnetic stimulation (TMS) was used to assess spinal root and cortical excitability as well as the effect of neurostimulation on anorectal sensation and pain, which were provoked by a local electrical stimulus. Initially, healthy volunteers received 6 stimulation paradigms in a randomised order (3 repetitive LSMS [1 Hz, 10 Hz, and sham]) and 3 repetitive TMS (1 Hz, 10 Hz, and sham) to investigate the effects on neural function and visceral sensation over 1 hour. The most effective cortical and spinal interventions were then applied in patients with IBS. Only 1-Hz rLSMS altered healthy anal motor excitability, increasing spinal (58 ± 12.3 vs 38.5 ± 5.7 μV, P = 0.04) but not cortical responses. Both 1-Hz rLSMS and 10-Hz repetitive transcranial magnetic stimulation increased healthy rectal pain thresholds for up to an hour after intervention (P < 0.05). When applied to patients with IBS, rectal pain thresholds were increased across all time points after both 1-Hz rLSMS and 10-Hz repetitive transcranial magnetic stimulation (P < 0.05) compared with sham. The application of magnetoelectric stimuli to the cortical and lumbosacral areas modulates visceral sensation in healthy subjects and patients with IBS. This proof-of-concept study provides supportive evidence for neurostimulation in managing functional gastrointestinal disorders.

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.

What's New in the Toolbox for Constipation and Fecal Incontinence?

Constipation and fecal incontinence (FI) are common complaints predominantly affecting the elderly and women. They are associated with significant morbidity and high healthcare costs. The causes are often multi-factorial and overlapping. With the advent of new technologies, we have a better understanding of their underlying pathophysiology which may involve disruption at any levels along the gut-brain-microbiota axis. Initial approach to management should always be the exclusion of secondary causes. Mild symptoms can be approached with conservative measures that may include dietary modifications, exercise, and medications. New prokinetics (e.g., prucalopride) and secretagogues (e.g., lubiprostone and linaclotide) are effective and safe in constipation. Biofeedback is the treatment of choice for dyssynergic defecation. Refractory constipation may respond to neuromodulation therapy with colectomy as the last resort especially for slow-transit constipation of neuropathic origin. Likewise, in refractory FI, less invasive approach can be tried first before progressing to more invasive surgical approach. Injectable bulking agents, sacral nerve stimulation, and SECCA procedure have modest efficacy but safe and less invasive. Surgery has equivocal efficacy but there are promising new techniques including dynamic graciloplasty, artificial bowel sphincter, and magnetic anal sphincter. Despite being challenging, there are no short of alternatives in our toolbox for the management of constipation and FI.

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.

Sacral neuromodulation therapy: a promising treatment for adolescents with refractory functional constipation

BACKGROUND

Sacral neuromodulation therapy has been successfully applied in adult patients with urinary and fecal incontinence and in adults with constipation not responding to intensive conservative treatment. No data, however, are available on sacral neuromodulation therapy as a treatment option in adolescents with refractory functional constipation.

OBJECTIVES

This study aimed to describe the short-term results of sacral neuromodulation in adolescents with chronic functional constipation refractory to intensive conservative treatment.

DESIGN

This is a retrospective review.

SETTING

This study took place at the Department of Surgery, Maastricht University Medical Centre, The Netherlands.

PATIENTS

Thirteen patients (all girls, age 10-18 years) with functional constipation according to the ROME III criteria not responding to intensive oral and rectal laxative treatment were assigned for sacral neuromodulation.

MAIN OUTCOME MEASURES

When improvement of symptoms was observed during the testing phase, a permanent stimulator was implanted. Patients were prospectively followed up to at least 6 months after implantation of the permanent stimulator by interviews, bowel diaries, and Cleveland Clinic constipation score. Improvement was defined as spontaneous defecation ≥ 2 times a week.

RESULTS

At presentation, none of the patients had spontaneous defecation or felt the urge to defecate. All patients had severe abdominal pain. Regular school absenteeism was present in 10 patients. After the testing phase, all but 2 patients had spontaneous defecation ≥ 2 times a week with a reduction in abdominal pain. After implantation, 11 (of 12) had a normal spontaneous defecation pattern of ≥ 2 times a week without medication, felt the urge to defecate, and perceived less abdominal pain without relapse of symptoms until 6 months after implantation. The average Cleveland Clinic constipation score decreased from 20.9 to 8.4. One lead revision and 2 pacemaker relocations were necessary.

LIMITATIONS

This study is limited by its small sample size, single-institution bias, and retrospective nature.

CONCLUSION

Sacral neuromodulation appears to be a promising new treatment option in adolescents with refractory functional constipation not responding to intensive conservative therapy. Larger randomized studies with long-term follow-up are required.

How sacral nerve stimulation works in patients with faecal incontinence

AIM

Sacral nerve stimulation (SNS) reduces incontinence episodes and improves the quality of life of patients treated for faecal incontinence. However, the exact mechanism of action of this technique remains unclear. The present article reviews the pertinent neuroanatomy and neurophysiology related to SNS and provides explanations for potential mechanisms of action.

METHOD

A systematic review of the literature was performed for studies of the potential mechanisms of action of SNS, using MEDLINE, PubMed, Embase and the Cochrane Library. Articles dealing with the technique, adverse events and economic evaluations of SNS, as well as literature reviews, were excluded, except for reviews dealing with the mechanisms of action of SNS. The following inclusion criteria were used to select articles: (i) articles in English, (ii) randomized, double-blinded, sham-controlled studies, and (iii) cohort studies. Case-control studies or retrospective studies were cited only when randomized or cohort studies could not be found.

RESULTS

We propose three hypotheses to explain the mechanism of action of SNS: (i) a somato-visceral reflex, (ii) a modulation of the perception of afferent information, and (iii) an increase in external anal sphincter activity.

CONCLUSION

The mechanism of action of SNS in patients with faecal incontinence almost certainly depends on the modulation of spinal and/or supraspinal afferent inputs. Further research on humans and animals will be required to gain a better understanding of the mechanisms of action of SNS.

Effects of neuromodulation with sacral magnetic stimulation for intractable bowel or bladder dysfunction in postoperative patients with anorectal malformation: a preliminary report

BACKGROUND AND PURPOSE

The effects of neuromodulation with sacral magnetic stimulation (SMS) were examined in postoperative patients with bowel or bladder dysfunction.

PATIENTS AND METHODS

SMS was performed at the S3 level using a MagPro® instrument (Medtronic Inc., USA) while the patients were under light sedation. One treatment course consisted of stimulation delivered at 15 Hz for 5 s, 10 times over an interval of 1 min. Three patients with bladder or bowel dysfunction refractory to conservative treatment were examined.

RESULTS

Case 1 is a 7-year-old male with a rectourethral fistula. This patient developed a hyperdynamic bladder after a laparoscopic pull-through operation at the age of 7 months. The administration of an anticholinergic agent slightly improved the condition. SMS was started at the age of 4 years with one trial each year. A marked expansion of bladder volume from 20 ml before trial to 120 ml after the third trial was obtained. Case 2 (a 4-year old female with a recto-vaginal fistula) and Case 3 (a 8-year-old female with an ano-vestibular fistula) showed severe constipation after radical surgery during infancy. Case 2 needed appendicostomy. After SMS, bowel movements could become controllable with enemas. No adverse effects were observed for any of the three cases.

CONCLUSIONS

These results suggest that SMS might be a useful modality to improve postoperative bowel or bladder dysfunction.

Sacral nerve stimulation increases activation of the primary somatosensory cortex by anal canal stimulation in an experimental model

BACKGROUND

Sacral and posterior tibial nerve stimulation may be used to treat faecal incontinence; however, the mechanism of action is unknown. The aim of this study was to establish whether sensory activation of the cerebral cortex by anal canal stimulation was increased by peripheral neuromodulation.

METHODS

A multielectrode array was positioned over the right primary somatosensory cortex of anaesthetized rats. A brief burst of electrical stimulation was applied to either the left sacral root or the left posterior tibial nerve, and evoked potentials from anal canal stimulation were signal-averaged at intervals over 1 h. At the end of the experiment, the cerebral cortex was removed and probed for polysialylated neural cell adhesion molecule (PSA-NCAM).

RESULTS

Sacral nerve root and posterior tibial nerve stimulation significantly increased the peak amplitude of primary cortical evoked potentials by 54.0 and 45.1 per cent respectively. This change persisted throughout the period of observation. The density of PSA-NCAM-positive cells in the somatosensory cortex underlying the electrode array was increased by approximately 50 per cent in the sacral nerve-stimulated group.

CONCLUSION

Brief sacral neuromodulation induces profound changes in anal canal representation on the primary somatosensory cortex, providing a plausible hypothesis concerning the mechanism of action of neuromodulation in the treatment of faecal incontinence.

Repetitive Lumbosacral Nerve Magnetic Stimulation Improves Bladder Dysfunction Due to Lumbosacral Nerve Injury

Background. Rapid rate magnetic stimulation of human sacral nerve roots can reduce stress incontinence. Objective. To test stimulation for urgency incontinence due to lumbosacral plexopathy. Methods. The authors studied patients with intractable neurogenic urinary dysfunction due to lumbosacral nerve injuries. Eligible patients were randomized to receive either real or sham repetitive lumbosacral magnetic stimulation (rLMS; 15 Hz with a total of 1500 pulses/session) for 10 sessions. Evaluation was performed before starting treatment, immediately after the 5th and 10th treatment session, and 1 month later, using rating scales to score urinary dysfunction and a visual analogue scale (VAS) to assess lower back pain. Posterior tibial nerve F-wave and H-reflexes were tested before and after treatment. Results. Both treatment and control groups were comparable for baseline characters and sphincteric disturbances. The mean number of voids and incontinence per 24 hours was significantly reduced in patients who received rLMS. The improvement was maintained 1 month after the end of treatment. Patients receiving real-rLMS also reported an improvement in VAS ratings. Improvement in F-wave and H-reflex latencies after real stimulation ( P = .002 and P = .036, respectively) was found as well. Conclusion. rLMS at 15 Hz may improve urinary dysfunction secondary to lumbosacral nerve injury. Further trials can determine the profile of patients who may benefit and optimal stimulation parameters.

Neuromodulation for constipation: sacral and transcutaneous stimulation

Constipation is a frequently occurring digestive ailment that is usually treated conservatively. Neuromodulation is altering function of an organ by altering neural activity. This paper reviews methods of neuromodulation used to treat constipation. This includes direct stimulation of sacral nerves and stimulation across the skin. Direct stimulation of sacral nerves is the most well developed method and is presented in detail. It is generally accepted that the mechanism of action is modulation rather than stimulation so it is called sacral neuromodulation (SNM). SNM involves percutaneous placement of an electrode in the third sacral foramen and implanting a stimulating device under the skin in the buttocks. SNM is founded on the physiological principle that activity in one neural pathway modulates pre-existing activity in another through synaptic interaction. The mechanism of action in constipation may be neuromodulation of the extrinsic neural control of the large bowel or modulation of reflexes inhibiting large bowel function. Limited evidence is available to assess the outcome of SNM in constipation. Results in the medium term seem promising for selected patients with idiopathic slow and normal transit constipation not responding to optimal conservative treatment. Adverse events include electrode migration and infection. The availability of a testing phase provides a predictor of treatment outcome. In addition, transcutaneous stimulation using sticky pad electrodes over the lumbosacral region or acupuncture points has been reported to improve constipation symptoms. In general, the level of evidence is low and further studies are needed.

Neurogenic bowel dysfunction: pathophysiology, clinical manifestations and treatment

Bowel dysfunction (e.g., fecal incontinence, infrequent or difficult defecation) are both frequent and severely troubling problems for patients with spinal cord injury, multiple sclerosis and Parkinson's disease. The etiology of these symptoms is complex; there may be autonomic and pelvic nerve dysfunction (with attenuation of voluntary motor function and impaired anorectal sensation and anorectal reflexes), or generalized systemic factors (e.g., altered diet and behavior, impaired mobility, psychological disturbances or drug adverse effects). The mainstay of current treatment is adapting a conservative approach towards reversing the systemic effects and optimizing the mechanics of defecation through the use of laxatives and irrigation approaches. When successful, this approach improves both evacuation and incontinence symptoms, with associated improvements in quality of life and independence. Future therapies may be directed at modulating pelvic innervation through electrical stimulation. Stoma formation remains an option for patients refractory to other approaches.

Neuromodulation for functional bowel disorders

In patients with functional bowel disorders not responding to maximal medical treatment, bowel lavage or biofeedback therapy, can nowadays be treated by sacral nerve neuromodulation (SNM). SNM therapy has evolved as a treatment for faecal incontinence and constipation. The exact working mechanism remains unknown. It is known that SNM therapy causes direct stimulation of the anal sphincter and causes changes in rectal sensation and several central nervous system areas. The advantage of SNM therapy is the ability to do a minimally invasive temporary screening phase to assess permanent stimulation outcome. Ideal candidates for SNM therapy are not known. Several studies have described positive and negative predictive factors, but the temporary screening remains the instrument of choice. Clinical results are good and as the technique is developing, fewer complications occur. New indications for SNM include constipation and anorectal or pelvic pain.