NEUROMODULATION REDUCES C-FOS GENE EXPRESSION IN SPINALIZED RATS: A DOUBLE-BLIND RANDOMIZED STUDY

[Functional-neurosurgical treatment options for functional pelvic floor disorders : Value of sacral neuromodulation]

BACKGROUND

Sacral neuromodulation is an established minimally invasive therapy indicated for the treatment of functional pelvic floor disorders. While it received its original US Food and Drug Administration (FDA) approval for the treatment of overactive bladder symptoms, it is now regarded as a therapeutic option to treat both urinary/fecal incontinence and retention. In addition, it has proven to be a valuable tool in the treatment of chronic pelvic pain, and preliminary results indicate a potential to elicit improvements in sexual functioning.

OBJECTIVE

This article serves to provide a summary of the therapy and its applications.

METHOD

Selective literature review.

RESULTS

Sacral neuromodulation implants allow for the controlled shifting of the autonomic control of bladder and rectum towards an inhibition or facilitation of voiding, dependent on the patient's needs and under the patient's control. At the same time and depending on the applied stimulation, the implants can interfere with the nerve's conduction of pain signals. This makes them a therapeutic option for pelvic pain that fails to respond to conventional treatment. Finally, there have been first reports suggesting improvements in sexual dysfunction under sacral neuromodulation, thus, potentially opening up a new line of therapy for those disorders.

DISCUSSION

Sacral neuromodulation is a flexible and efficient form of therapy for functional disorders of the pelvic floor. Specifically, the same intervention can treat seemingly contradictory disorders such as urinary/fecal incontinence and retention as well as chronic pain.

Acupuncture for Women with Overactive Bladder: Perspective of Traditional Chinese Medicine and Related Mechanism

Purpose

Overactive bladder (OAB) syndrome is one of the most common diseases in urology and affects quality of life. Although the current treatment for OAB is based on oral medications, there are limitations and many patients have difficulty accepting drug-induced adverse effects. This review aimed to analyze the efficacy of acupuncture and its related mechanisms and provide a preliminary therapeutic regimen.

Methods

Two authors independently searched PubMed, Embase, and Cochrane Library up to April 2022. They searched related English literature and extracted the data under a standard form based on the search strategy. Clinical trials which included OAB women with the treatment of acupuncture were included. Common acupuncture alone without other pharmacotherapy, external treatments was in the treatment group. The control interventions may include any active treatments, sham placebo, or no establishment of a control group. Outcomes included 3-day or 24-hour voiding diary, overactive bladder symptom score, etc. The Cochrane risk of bias tool was also used to assess the methodological quality of the randomized controlled trials (RCTs).

Results

We analyzed five RCTs and one comparative study on acupuncture for OAB to review and discuss the acupoint location, treatment course, and retention time based on clinical evidence and treatment ideas in traditional Chinese medicine. Additionally, we used the available evidence to reveal and discuss the acupuncture mechanisms for OAB. Acupuncture may regulate bladder function by inhibiting C-fibers, modulating nerve growth factors and reducing spontaneous contractions of the detrusor muscle.

Conclusion

Combined with the available evidence, the combination of local acupoints and distal acupoints should be necessary to consider, especially the lumbosacral acupoints, the small abdomen acupoints and the lower limb acupoints. Among them, acupuncture at SP4, CV4 and KI3 are strongly recommended. The treatment course of acupuncture should be no less than 4 weeks and maintain the frequency of acupuncture no less than once a week. The duration of each session should be no less than 20 minutes. In addition, investigations remain necessary to verify acupuncture's efficacy and precise mechanism for OAB treatment in further exploration.

The projection of anorectal afferents to spinal cord and effect of sacral neuromodulation on dorsal horn neurons which receive such input in the rat

BACKGROUND

The rat has served usefully as a model for fecal incontinence and exploration of the mechanism of action of sacral neuromodulation (SNM). There remains a deficit in information regarding the location and type of spinal neurons which receive anorectal input and the effect of SNM on those neurons.

METHODS

Single neuronal extracellular recordings of neurons receiving anorectal input were made at the S1 level of the spinal cord using sharp glass electrodes. SNM at S1 was delivered at 2 Hz for 3 minutes and its effect on discharge was quantified.

KEY RESULTS

In total, 31 units (n = 14 animals) receiving anorectal synaptic input were recorded at the first sacral (S1) segmental level in either lamina III or IV of the dorsal horn. The inputs were classified according to afferent fiber conduction speed (16 Aδ, 11 Aβ, and 4 C-fiber). The baseline firing frequency (ie, the mean firing frequency before the application of SNM) was 0.48 Hz ± 0.49 (mean ± SD) and 58% of units responded to acute SNM with either an increase or decrease in mean firing frequency.

CONCLUSIONS & INFERENCES

In this study, the majority of spinal neurons receiving anorectal input changed their activity in response to SNM. These findings provide the basis for future studies which aim to explore the precise cellular mechanism of action of SNM on this fecal continence pathway.

Effect of Early Sacral Neuromodulation on Bladder Function in a Rat Model of Incomplete Spinal Cord Injury Due to Focal Contusion

OBJECTIVES

Incomplete spinal cord injury (SCI) accounts for two-thirds of all SCIs in clinical practice. Preclinical research on the effect of sacral neuromodulation (SNM) on bladder function, however, has been focused only on animal models of complete SCI. We aimed to evaluate the effect of early SNM on bladder responses in a rat model of incomplete SCI.

MATERIALS AND METHODS

Altogether, 21 female Sprague-Dawley rats were equally assigned to control (CTR), SCI + sham stimulation (SHAM), and SCI + SNM (SNM) groups. In the SHAM and SNM groups, incomplete SCI was created by producing a moderate contusion with an NYU-MASCIS impactor at the T9-T10 level of the spine, with needle electrodes implanted bilaterally into the S2 or S3 sacral foramen. Only SNM group underwent electrical stimulation for 28 days, beginning on day 7 after SCI. Cystometry was performed 35 days after SCI.

RESULTS

Although the interval between voiding contractions was significantly longer in the SHAM group than the CTR group (25.5 ± 1.4 vs. 12.5 ± 1.7 min; p < 0.05), there were no significant differences between the SNM group (16.5 ± 1.5 min) and the CTR group. Maximum voiding contraction pressure did not differ among the groups. The SNM group had a significantly lower frequency (3.5 ± 0.5 vs. 14.6 ± 2.0; p < 0.05) and maximum pressure (11.4 ± 6.2 vs. 21.3 ± 1.8 cmH₂ O; p < 0.05) of nonvoiding contractions than the SHAM group.

CONCLUSIONS

Our results provide experimental evidence that early SNM treatment may prevent or diminish bladder dysfunctions (e.g., detrusor overactivity, abnormal micturition reflex) in a clinical condition of incomplete SCI.

Efficacy of different spinal nerve roots for neuromodulation of micturition reflex in rats

Electrical stimulation of peripheral nerves controlling the bladder is an alternative, nondestructive medical treatment for urinary incontinence and retention. In this study, we aimed to identify the most efficient sensory and motor spinal nerve roots involved in the micturition reflex. Unilateral L5-S2 dorsal and ventral roots were electrically stimulated, and bladder reflex contractions were recorded under isovolumetric conditions. Repeated stimulation of the L6 and S1 dorsal roots not only abolished bladder reflex contractions but also induced a poststimulation inhibitory effect, whereas repeated stimulation of the L5 and S2 dorsal roots had no effect. Only the L6 ventral root directly caused bladder contraction when ventral roots L5-S2 were stimulated in sequence. Upon retrograde tracing using pseudorabies virus (PRV), the sacral parasympathetic nucleus of the L6 segment had more PRV-positive cells than the other segments, though the S1 segment of the dorsal root ganglia had the highest density of PRV-positive neurons. These results suggest the L6 ventral root is most efficient in producing detrusor muscle contraction, and the S1 dorsal root best inhibits the micturition reflex.

High-power Magnetotherapy: A New Weapon in Urinary Incontinence?

OBJECTIVE

Urinary incontinence (UI) is one of the most common urinary system diseases that mostly affects women but also men. We evaluated the therapeutic efficacy of functional magnetic stimulation (FMS) as potential UI treatment with improvements in the pelvic floor musculature, urodynamic tests and quality of life.

METHODS

A total of 20 UI patients (10 females and 10 men, mean age 64, 14 years), including 10 with stress UI, four with urgency UI and six with mixed UI, were treated with FMS (20 min/session) twice a week for 3 weeks. The patients' impressions, records in urinary diaries, and scores of three life stress questionnaires (overactive bladder symptom questionnaire [OAB-q], urogenital distress inventory questionnaire-short form [UDI-6], incontinence impact questionnaire-short form [IIQ-7]) were performed pre- and post-treatment.

RESULTS

Significant reductions (P < 0.01) of micturition number and nocturia after magnetic treatment were evidenced. The urodynamic tests recorded a significant increase in cystometric capacity (147 ± 51.3%), in maximum urethral closure pressure (110 ± 34%), in urethral functional length (99.8 ± 51.8%), and in pressure transmission ratio (147 ± 51.3%) values compared with the baseline values.

CONCLUSIONS

These preliminary findings suggest that FMS with Magneto STYM (twice weekly for 3 weeks) improves the UI and may be an effective treatment for this urogenital disease.

Electrical Stimulation of the Spinal Dorsal Root Inhibits Reflex Bladder Contraction and External Urethra Sphincter Activity: Is This How Sacral Neuromodulation Works?

INTRODUCTION

Using a rat model, we aimed to confirm the inhibitory effect of dorsal spinal root (afferent) stimulation and test if bilateral stimulation is more effective than unilateral stimulation. External urethral sphincter (EUS) electromyography (EMG) is also assessed in conjunction with cystometrogram.

MATERIALS AND METHODS

Eighteen female Sprague-Dawley rats were tested following urethane anesthesia. Via urethral catheterization, the bladder was infused with normal saline to evoke rhythmic bladder reflex contractions (BRC). L6 spinal nerves were isolated and stimulated.

RESULTS

L6 stimulation was effective in inhibiting BRC. L6 bilateral dorsal root (DR) stimulation of 50% intensity was required to cause inhibition as compared to unilateral stimulation. In EUS EMG recordings, there was a strong association between EUS EMG activities and bladder contraction. When the bladder contraction was inhibited effectively by L6 DR stimulation, a considerable reduction was also found in the EUS EMG activities.

CONCLUSIONS

L6 DR stimulation abolished BRC in our rat model. Bilateral L6 DR stimulation produced a 50% reduction in stimulation intensity, providing a similar BRC block. Abolishing BRC also appeared to coincide with a reduction in EUS EMG, implicating that sacral neuromodulation might act centrally, at least rostrally at the T8-9 spinal level.

Reflex neuromodulation of bladder function elicited by posterior tibial nerve stimulation in anesthetized rats

Although posterior tibial nerve stimulation (PTNS) has been shown in both clinical and animal studies to elicit bladder-inhibitory reflexes, our understanding of the role of posterior tibial nerve (PTN) afferents that elicit these responses is significantly limited. To this end, we investigated the effects of frequency-dependant PTNS in urethane-anesthetized rats undergoing repeated urodynamic fills. Nerve stimulation trials (10 min) resulted in statistically significant inhibition of the urinary bladder, both during and after nerve stimulation ( P < 0.05). PTNS applied at 5 Hz resulted in both acute and prolonged changes that corresponded to 38.0% and 34.1% reductions in the bladder contraction frequency, respectively. In contrast, PTNS applied at 10 Hz could only elicit an acute decrease (22.9%) in bladder activity. Subsequent electrical activation of individual PTN branches (lateral or medial plantar nerves) confirmed that these bladder reflexes are mediated by specific subsets of the PTN trunk. Both acute and prolonged inhibition of the bladder were achieved by electrical stimulation of the lateral plantar (10 and 20 Hz) and medial plantar (5 and 10 Hz) nerves. Finally, we report a bladder-excitatory reflex that is elicited by electrical activation of either the PTN trunk or lateral plantar nerve at 50 Hz. This study shows that multiple bladder reflexes are tuned to specific subsets of nerve afferents and stimulation frequencies, each of which provide novel insights into the physiological effects of PTNS.

Sacral nerve modulation for fecal incontinence: results of a prospective single-center randomized crossover study

BACKGROUND

Although sacral nerve modulation has become an important tool for the treatment of fecal incontinence, prospective, randomized data are still rare.

OBJECTIVE

To determine the effectiveness of sacral nerve modulation in a prospective randomized crossover study

DESIGN

: Prospective randomized crossover study

SETTING

: Proctological Office and Department of Surgical Proctology at a private hospital.

PATIENTS

A total of 31 consecutive patients (31 women) aged 55 ± 12 years (median ± SD) with fecal incontinence were enrolled between February 2012 and December 2012.

INTERVENTIONS

All patients underwent sacral nerve modulation through a staged implantation procedure between 2009-2011. After a median of 26.8 months following implantation, 16 of the 31 patients agreed to be randomized in a crossover design to stimulation ON or OFF, each for a 3-week period. After the two periods (ie, 6 weeks), while still blinded to the stimulator status, the patients chose which stimulation period (first or second) they preferred. The mode of stimulation corresponding to the selected period was then continued for 3 months (final period).

MAIN OUTCOME MEASURES

Frequency of bowel movements, frequency of fecal incontinence and urgency episodes, severity scores, preference for ON or OFF.

RESULTS

The frequency of fecal incontinence episodes and Cleveland Clinic Incontinence Score (CCIS) were both significantly lower in the ON period than the OFF period (p < 0.005) during the crossover phase of the study. All patients decided to stay in the ON mode for the final period and have continued in the ON mode until now.

LIMITATIONS

Small patient numbers.

CONCLUSIONS

The significant improvement in fecal incontinence during the ON period, as compared to the OFF period, makes it unlikely that the observed benefits of sacral nerve modulation are due to a placebo effect.

Effects of sacral neuromodulation on isolated urinary bladder function in a rat model of spinal cord injury

INTRODUCTION

Sacral neuromodulation has been considered as an effective treatment option for various types of chronic voiding dysfunction, but the mechanism of action has not been well understood. The aim of this study was to evaluate the effect of chronic sacral neuromodulation on isolated bladder functions in a rat model of spinal cord injury.

MATERIALS AND METHODS

Female Sprague-Dawley rats (250-300 g; N = 20) were assigned to four groups as follows: 1) control group (N = 6); 2) spinal cord transection group (SCT; N = 5); 3) spinal cord transection + sacral neuromodulation group (SCT + SNM; N = 5); 4) sham (spinal cord transection + electrode wire implantation without sacral neuromodulation; N = 4). The rats in the SCT, SCT + SNM, and sham groups were anesthetized with ketamine (60 mg/kg, i.p.) and xylazine (7 mg/kg, i.p.). The spinal cord was completely transected at T8-T9 level in SCT and SCT + SNM groups. Electrode wires were implanted into S3 dorsal foramina in both sham and SNM groups, but only the SNM group was subjected to electrical stimulation for four hours a day for three weeks. Twenty-one days later, the rats were sacrificed via anesthetic overdose, and isolated longitudinal bladder strip preparations were placed in organ baths for the investigation of their isometric responses to pharmacological agents.

RESULTS

In isometric contraction experiments, SCT was found to increase the contraction responses of the bladder strips to muscarinic stimulation, and SNM could not prevent this increase. In isometric relaxation experiments, SCT caused a decrease in β-adrenergic relaxation responses, and SNM augmented the bladder's β-adrenergic relaxation responses. Nitric oxide did not affect the relaxation responses.

CONCLUSION

In our rat model of SCT, SNM seemed to alter adrenergic receptor function in the urinary bladder. Further studies are required to clarify the mechanism of these alterations at the level of bladder receptors following sacral neuromodulation.

Does our limited knowledge of the mechanisms of neural stimulation limit its benefits for patients with overactive bladder? ICI-RS 2013

INTRODUCTION

Neural stimulation has become an established minimally invasive treatment for various lower urinary tract symptoms. The results both short- and long-term are encouraging, however, there is still a lack of knowledge of obvious risk factors, which may affect the outcome of treatment. Although neural stimulation has been embraced by healthcare professionals and patients, the exact mechanism by which neural stimulation works is still unclear.

DISCUSSION

A condense review of knowledge available on this topic is presented. Several research questions are raised. Outlines of research studies, both clinical and basic science, are suggested.

CONCLUSIONS

Further studies are necessary to understand mechanism of action of neural stimulation and its implications on treatment outcomes.

Neuromodulation attenuates bladder hyperactivity in a rat cystitis model

BACKGROUND

We investigated the regulation of urinary bladder function by electrical stimulation of the L6 spinal nerve (SN) using cystometry in normal rats and in rats with cystitis induced by intravesical infusion of dilute acetic acid.

METHODS

In anesthetized rats, a cannula was placed into the bladder dome for saline/acetic acid infusion and intravesical pressure monitoring. Threshold pressure (TP), basal pressure (BP) and inter-contraction interval (ICI) were measured from the bladder pressure recording and void volume (VV) was measured by weighing the voided fluid.

RESULTS

Comparison of cystometrograms obtained with infusion of saline or acetic acid showed that acetic acid decreases TP, ICI and VV. These excitatory effects, characteristic of acetic acid induced bladder hyperactivity, were significantly reversed by bilateral SN stimulation (P <0.05, vs pre-stimulation, Student t-test). In saline perfused rats, one hour of bilateral SN stimulation at 10 Hz and at motor threshold (0.19 ± 0.01 milliamps) increased ICI (265%) and VV (217%). In rats perfused with acetic acid, the corresponding increases produced by SN stimulation were 350% for ICI and 383% for VV. The percentage increases in the acetic acid-treated group were not significantly higher than those in saline-treated group.

CONCLUSIONS

Using continuous flow cystyometry, we find that SN stimulation can produce effects on micturition consistent with its effects on isovolumetric model, and consistent with the therapeutic effect observed with InterStim® therapy in overactive bladder patients. Although the effect of SN stimulation was slightly greater in bladder irritated over normal rats, the difference was not statistically significant.

Neural pathways involved in sacral neuromodulation of reflex bladder activity in cats

This study examined the mechanisms underlying the effects of sacral neuromodulation on reflex bladder activity in chloralose-anesthetized cats. Bladder activity was recorded during cystometrograms (CMGs) or under isovolumetric conditions. An S1-S3 dorsal (DRT) or ventral root (VRT) was electrically stimulated at a range of frequencies (1-30 Hz) and at intensities relative to threshold (0.25-2T) for evoking anal/toe twitches. Stimulation of DRTs but not VRTs at 1T intensity and frequencies of 1-30 Hz inhibited isovolumetric rhythmic bladder contractions. A 5-Hz DRT stimulation during CMGs was optimal for increasing (P < 0.05) bladder capacity (BC), but stimulation at 15 and 30 Hz was ineffective. Stimulation of the S1 DRT was more effective (increases BC to 144% and 164% of control at 1T and 2T, respectively) than S2 DRT stimulation (increases BC to 132% and 150% of control). Bilateral transection of the hypogastric or pudendal nerves did not change the inhibitory effect induced by S1 DRT stimulation. Repeated stimulation of S1 and S2 DRTs during multiple CMGs elicited a significant (P < 0.05) increase in BC (to 155 ± 11% of control) that persisted after termination of the stimulation. These results in cats suggest that the inhibition of reflex bladder activity by sacral neuromodulation occurs primarily in the central nervous system by inhibiting the ascending or descending pathways of the spinobulbospinal micturition reflex.

Effects of acute sacral neuromodulation on bladder reflex in complete spinal cord injury rats

BACKGROUND

Neurogenic bladder associated with spinal cord injury (SCI) often results in serious disruption of lower urinary tract function. Compared to conventional therapies, sacral neuromodulation (SNM) may offer an alternative, non-destructive treatment for SCI patients with bladder dysfunction. Understanding bladder reflex changes following SCI and the effects of SNM may yield new insights for innovative use of this promising technique. Using a SCI rat model developed in this study, we investigated: 1) the bladder responses with different grades of bladder filling in intact and SCI rats; and 2) the effects of acute SNM on bladder reflex responses in SCI rats.

METHODS

An SCI rat model with overactive bladder was developed and evaluated in this study to examine the effects of acute SNM on bladder reflex in complete SCI rats. Twelve adult female Sprague-Dawley rats were divided into three groups; group I: spinally intact rats (N = 4), group II: transected (T9-T10) rats (N = 4), i.e., SCI rats, and group III: SCI rats with SNM treatment (N = 4). All rats were anesthetized and set up for continuous saline infusion. Cystometric parameters, including contraction period, contraction duration, bladder peak pressure, and number of uninhibited contractions, were analyzed and compared between groups and between conditions with and without SNM treatment for SCI rats.

RESULTS

In the intact rats, the frequency of bladder contraction was dependent upon the rate of bladder filling, while the spinal transected rats exhibited large fluctuation and demonstrated different patterns in response to saline infusion. Moreover, the bladder in SCI rats demonstrated an increased contraction period and a decreased contraction strength compared to the intact rats (all p < 0.05). In SCI rats under acute SNM treatment, bladder contraction period and duration tended to become longer, and the bladder peak pressure was decreased. The accumulating evidence indicated that acute SNM had inhibiting effects for bladder overactivity following SCI.

CONCLUSION

The spinal rat model developed in this study was suitable to investigate the effect of sacral neural stimulation on micturition reflex. The results of present study demonstrated that the micturition reflex can be modulated by sacral neural stimulation.

Neuromodulation in a rat model of the bladder micturition reflex

A rat model of bladder reflex contraction (BRC) was used to determine the optimal frequency and intensity of spinal nerve (SN) stimulation to produce neuromodulation of bladder activity and to assess the therapeutic mechanisms of this neuromodulation. In anesthetized female rats (urethane 1.2 g/kg ip), a wire electrode was used to produce bilateral stimulation of the L6 SN. A cannula was placed into the bladder via the urethra, and the urethra was ligated to ensure an isovolumetric bladder. Saline infusion induced BRC. Electrical stimulation of the SN produced a frequency- and intensity-dependent attenuation of the frequency of bladder contractions. Ten-herz stimulation produced maximal inhibition; lower and higher stimulation frequency produced less attenuation of BRC. Attenuation of bladder contraction frequency was directly proportional to the current intensity. At 10 Hz, stimulation using motor threshold pulses (T(mot)) produced a delayed inhibition of the frequency of bladder contractions to 34 ± 11% of control. Maximal bladder inhibition appeared at 10 min poststimulation. High current intensity at 0.6 mA (∼6 * T(mot)) abolished bladder contraction during stimulation, and the inhibition was sustained for 10 min poststimulation (prolonged inhibition). Furthermore, in rats pretreated with capsaicin (125 mg/kg sc), stimulation produced a stronger inhibition of BRC. The inhibitory effects on bladder contraction may be mediated by both afferent and efferent mechanisms. Lower intensities of stimulation may activate large, fast-conducting fibers and actions through the afferent limb of the micturition reflex arc in SN neuromodulation. Higher intensities may additionally act through the efferent limb.

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.

Electrical nerve stimulation for overactive bladder in children

Overactive bladder (OAB) is a urological condition that is frequently observed in children and requires treatment. Standard urotherapy is usually the first line of treatment; however, children with severe OAB do not respond to this therapy. Antimuscarinic drugs may be used, but complete resolution of symptoms with this medication is low. Studies, including two randomized clinical trials, have demonstrated that electrical nerve stimulation (ENS) can be used successfully for OAB in children. Electrodes have been placed in the genitals, anus, and intravesical area, and on the tibial posterior nerve, as well as used transcutaneously or implanted during a surgical procedure. This Review will discuss the use of ENS in children with OAB, with particular focus on the putative mechanisms of action, the different ENS techniques available, and clinical results for this therapy.

Mechanisms of action of sacral neuromodulation

The lower urinary tract dysfunction encompasses voiding, postvoiding, and storage symptoms. Conventional treatment modalities include pharmacotherapy and behavioural therapy. Sacral neuromodulation (SNM) is a safe and minimally invasive treatment modality that has recently gained wide acceptance in the management of urinary urge incontinence, urge frequency, and nonobstructive urinary retention, in particular, among those patients with conditions refractory to conventional methods. We searched multiple electronic databases through June 30, 2009 for eligible studies. We examined published clinical and experimental studies concerning the mechanisms of action of SNM. In the first part of the manuscript, we describe the anatomy and functions of the lower urinary tract including the reflexes involved in its functions and then review the pathophysiology of major types of the lower urinary tract dysfunction. In the second part, we discuss different ways for SNM to control various types of voiding dysfunction. The lower urinary tract dysfunctions affect millions of people worldwide and have a severe impact on their quality of life. SNM offers a safe and minimally invasive modality in the treatment of voiding dysfunctions, especially in patients with conditions refractory to conventional therapies.

Activity and Expression of Nitric Oxide Synthase in Rat Bladder after Sacral Neuromodulation

The aim of our study is to investigate the effects of chronic sacral neuromodulation on Nitric Oxide (NO) metabolism in the rat bladder. 26 female Sprangue-Dawley rats were considered: group I, normal control rats; group II, a sham treatment, in whom catheters for electrical stimulation were placed in the S1 foramen bilaterally and left in place for 21 days, without performing neuromodulation; group III in whom electrical sacral neuromodulation was performed for 21 days. Finally a cystectomy was performed and the bladder biopsy specimens were sent for immunostaining with n-NOS and i-NOS. Morphological and immunohistochemical analysis was carried out, and evaluated in urothelial cells, endothelial cells and muscle fibers of the muscularis propria. Differences between the 3 groups were analyzed by Student Newman-Keuls test. We could observe that urothelial and endothelial i-NOS (37.00±4.69 and 59.00±7.42 respectively) and urothelial n-NOS (36.80±7.85) expression are significantly increased in neuromodulated rats, compared to groups 1 and 2 (p < 0.005). In conclusion, the increase of i-NOS expression on endothelial cells after sacral neuromodulation could be in some way related to angiogenetic responses in the microvascular structures; the increase of n-NOS and i-NOS expression on urothelial cells can suggest that NO is able to influence the plasticity of bladder response, inducing the release of messengers within the urothelium. This study can therefore improve our understanding of the mechanisms of sacral neuromodulation on chronic bladder dysfunction; further studies will need to better demonstrate the role of angiogenesis in the bladder after sacral neuromodulation and to investigate the effects of neuromodulation in rats with chronically induced bladder dysfunction.

Topographic anatomy of a new posterior approach to the pudendal nerve for stimulation

OBJECTIVES

To describe a new approach to the pudendal nerve from a dorsal direction in terms of topographic anatomy and to discuss pudendal nerve neurophysiology in light of the rationale behind pudendal nerve stimulation to treat lower urinary tract disorders.

MATERIALS AND METHODS

Cadavers of four women aged 78-87 yr were studied. After placing the cadavers in prone position with a 40 degrees -60 degrees flexion of the hips and determining anatomic landmarks, a 20-G insulated needle was inserted close to the pudendal nerve. Then the topographic relationships of the puncture with the pudendal canal were explored by dissection.

RESULTS

The mean points of insertion of the needle were 14 cm inside the great trochanter, 9 cm above the ischiatic tuberosity, and 6 cm outside the gluteal fold. If the needle was inserted 6.5 cm under the previous with an orifice of 60 degrees and this route was followed, the needle could have a contact area with the pudendal nerve larger, leading to a greater stimulation efficacy with less stimulation intensities. The rectum was so far away that a rectal injury with the needle seemed unlikely. No vascular structure was at the contact of the nerve.

CONCLUSIONS

The described new puncture technique to reach the pudendal nerve provides easy and safe accessibility of the nerve for stimulation. In light of our increasing understanding of the rationale behind neuromodulative stimulation, the pudendal nerve could be a promising target for continuous lower urinary tract neuromodulation by implant.

Electrical neuromodulatory therapy in female voiding dysfunction

Female voiding dysfunction such as urge-frequency syndrome, urge incontinence and unobstructive urinary retention are often refractory to conservative management. Electrical neuromodulation with surface electrodes or with implantable systems has become a valuable addition to the therapeutic options in the last two decades. Interstitial cystitis is an emerging indication. The application of these techniques in non-neurogenic patients is reviewed. The techniques using unimplantable electrodes, anogenital electrical stimulation with plug electrodes, transcutaneous electrical nerve stimulation with surface electrodes, and posterior tibial nerve stimulation using needle electrodes are addressed. Several techniques using implantable systems are discussed, e.g. sacral nerve neuromodulation (Interstim device), pudendal nerve stimulation (Interstim and Bion device) and paraurethral neuromodulation (Miniaturo device). The long-term efficacy of neuromodulation for the established indications is more than half, but 20-50% of the patients initially tested do not respond to a test procedure. The disadvantage is the high surgical revision rate and the high cost of treatment. Technical advances will hopefully be able to address these aspects.

Current opinion on the working mechanisms of neuromodulation in the treatment of lower urinary tract dysfunction

PURPOSE OF REVIEW

Neuromodulation is a successful treatment for patients with refractory lower urinary tract dysfunction. In the recent years, more applications of various types and ways have been developed and put into clinical practice. It is important, therefore, for urologists to know the existing theories on the working mechanisms that explain the effect. Although much research has been devoted to this subject for the past 35 years, the working mechanism is still unknown. This review presents an overview of the different theories and research into the physiological background of neuromodulation during the past 3 decades with emphasis on recent developments.

RECENT FINDINGS

Specific receptors in the spinal cord have been identified, which are involved in the working mechanism of neuromodulation. The maximal effect of neuromodulation is not directly reached, indicating that neuromodulation induces learning changes (i.e. neural plasticity). The carry-over effect could be caused by negative modulation of excitatory synapses in the central micturition reflex pathway.

SUMMARY

Neuromodulation in the treatment of stress incontinence probably induces physiological changes in the sphincter muscles and pelvic floor. In the treatment of overactive bladder syndrome, nonobstructive voiding dysfunction and chronic pelvic pain, the mechanism of action seems to be more complicated. Most likely, it is a combination of the different suggested modes of action, involving the neuroaxis at different levels.

Efficacy of sacral nerve stimulation for fecal incontinence: results of a multicenter double-blind crossover study

BACKGROUND AND AIMS

This is the first double-blind multicenter study examining the effectiveness of sacral nerve stimulation in a significant number of fecally incontinent patients.

METHODS

A total of 34 consecutive patients (31 women), median age 57 years (range, 33-73 years), underwent sacral nerve stimulation for fecal incontinence. After implantation, 27 of 34 patients were randomized in a double-blind crossover design to stimulation ON or OFF for 1-month periods. While still blinded, the patients chose the period of stimulation (ON or OFF) that they had preferred. The mode of stimulation corresponding to the selected period was continued for 3 months (final period). Outcome measures were frequency of fecal incontinence and urgency episodes, delay in postponing defecation, score severity, feeling of improvement, preference for ON or OFF, quality of life, and manometric measurements.

RESULTS

In the crossover portion of the study, the self-reported frequency of fecal incontinence episodes was significantly reduced during the ON versus the OFF period (P = 0.03), and this symptomatic improvement was consistent: 1) with the patients feeling of greater improvement during the ON versus OFF period (P = 0.02); 2) with the significant preference of patients (P = 0.02) for the ON versus OFF period. In the final period of the study, the frequency of fecal incontinence episodes decreased significantly (P = 0.005) in patients with the stimulator ON. The ability to postpone defecation (P = 0.01), the score for symptom severity (P = 0.0004), and the quality of life (P < 0.05) as well as anal sphincter function significantly improved.

CONCLUSIONS

The significant improvement in FI during the ON versus OFF period indicated that the clinical benefit of sacral nerve stimulation was not due to placebo.

A critical review on magnetic stimulation: what is its role in the management of pelvic floor disorders?

PURPOSE OF REVIEW

This review looks at the acute effects of magnetic stimulation on urodynamic parameters and reviews the data on its use in the management of urinary incontinence.

RECENT FINDINGS

Reported cure rates for stress incontinence immediately after a course of perineal magnetic stimulation range from 12.5 to 52.9% with good improvement occurring in 32% to 41%. However the effect seems temporary and dependent on the number of sessions. Sacral and pelvic floor magnetic stimulation have also been shown to increase cystometric capacity, inhibit detrusor overactivity and resolve overactive bladder symptoms acutely. Persistence of this effect with symptomatic improvement one week after sacral magnetic stimulation has been demonstrated. How magnetic stimulation suppresses detrusor contraction is not known. Prospective trials with the Neocontrol chair (Neotonus Inc, Marietta, Georgia, USA) also showed symptomatic improvement in 71 to 87% in the short term. However, the longer term data appear mixed.

SUMMARY

Overall, the data available vary too much in terms of treatment protocols, patient mix and symptom severity to determine which group of patients might benefit most and what the optimal stimulation parameters are for each condition. Mean reductions in leak parameters, although statistically significant, may not always be clinically satisfactory. The beneficial effects also appear to be temporary and continuous treatment will probably be required. Further trials are needed to determine the optimum stimulation protocols for different situations and to compare magnetic stimulation with other forms of conservative pelvic floor therapy.

Artificial autonomic reflexes: using functional electrical stimulation to mimic bladder reflexes after injury or disease

Autonomic reflexes controlling bladder storage (continence) and emptying (micturition) involve spinal and supraspinal nerve pathways, with complex mechanisms coordinating smooth muscle activity of the lower urinary tract with voluntary muscle activity of the external urethral sphincter (EUS). These reflexes can be severely disrupted by various diseases and by neurotrauma, particularly spinal cord injury (SCI). Functional electrical stimulation (FES) refers to a group of techniques that involve application of low levels of electrical current to artificially induce or modify nerve activation or muscle contraction, in order to restore function, improve health or rectify physiological dysfunction. Various types of FES have been developed specifically for improving bladder function and while successful for many urological patients, still require substantial refinement for use after spinal cord injury. Improved knowledge of the neural circuitry and physiology of human bladder reflexes, and the mechanisms by which various types of FES alter spinal outflow, is urgently required. Following spinal cord injury, physical and chemical changes occur within peripheral, spinal and supraspinal components of bladder reflex circuitry. Better understanding of this plasticity may determine the most suitable methods of FES at particular times after injury, or may lead to new FES approaches that exploit this remodeling or perhaps even influence the plasticity. Advances in studies of the neuroanatomy, neurophysiology and plasticity of lumbosacral nerve circuits will provide many further opportunities to improve FES approaches, and will provide "artificial autonomic reflexes" that much more closely resemble the original, healthy neuronal regulatory mechanisms.

The management of female voiding dysfunction: Fowler's syndrome -- a contemporary update

PURPOSE OF REVIEW

Several aspects of voiding dysfunction in women remain under investigation, including standardization of the diagnosis and management of bladder outflow obstruction. This article describes a specific cause of urinary retention in young women, associated with a failure of urethral sphincter relaxation, and a treatment option that can restore voiding in this group of patients - sacral nerve electrical stimulation therapy. Recently there have been advances in the stimulator implantation technique, as well as in our appreciation of its mechanism of action.

RECENT FINDINGS

Advances include the use of ancillary investigations such as urethral function tests as well as better understanding of the clinical profile of these patients. Improvements in the surgical technique include better methods of lead fixation and a less invasive surgical approach. Research suggests the action of neuromodulation is on the afferent pathway, though it remains to be shown whether this is at a spinal or supraspinal level. It is likely that sacral nerve stimulation has an indirect modulatory effect on detrusor contractility rather than a direct effect on the sphincter.

SUMMARY

Experience of sacral nerve stimulation has increased over the past few years, and its application is expanding to other clinical domains. This knowledge has helped improve the therapy, which is particularly effective in the treatment of women with urinary retention. Although how it works is still not fully understood, this is something that is being addressed by ongoing research.

Change of vanilloid receptor 1 following neuromodulation in rats with spinal cord injury

BACKGROUND

Neuromodulation has been used to treat voiding dysfunction caused by spinal cord injury (SCI). However, the underlying mechanism of this technique is not well understood. Recently, vanilloid receptor 1 (VR1) has been recognized as a capsaicin receptor and an agent for noxious stimuli. The purposes of this study were to evaluate whether development of bladder hyperreflexia after SCI involves VR1 upregulation and whether VR1 is involved in the process of neuromodulation.

MATERIALS AND METHODS

Sprague-Dawley rats (n = 20) were divided into five groups: sham control (n = 4); 3 days after SCI (n = 4); 7 days after SCI (n = 4); 14 days after SCI (n = 4), and 14 days after SCI with neurostimulation (n = 4). Bilateral electrode wires were implanted into S1 dorsal foramina and electrical stimulation was performed 8 h/day for 2 weeks. Spinal segments of L6, S1, and dorsal root ganglia were removed and cut into sections. The intensity of VR1 staining was evaluated by image analysis.

RESULTS

VR1-positive staining was confined to the superficial dorsal horn of the spinal cord. The staining was weak in the sham group (1/luminosity: 0.0050 +/- 0.0006), but the staining intensity was significantly increased in three SCI groups (3 days, 7 days, and 14 days) when compared with that in the sham group (P < 0.05). After neuromodulation, the staining intensity was reduced.

CONCLUSIONS

VR1 expression in the spinal cord is up-regulated after SCI. Sacral nerve root stimulation can down-regulate the VR1 expression.

Magnetic stimulation of the sacral roots for the treatment of urinary frequency and urge incontinence: an investigational study and placebo controlled trial

PURPOSE

We designed an investigational study and placebo controlled trial to evaluate the efficacy of magnetic stimulation of the sacral roots for treating urinary frequency and urge incontinence.

MATERIALS AND METHODS

A total of 48 women 43 to 75 years old (mean age 61) with the complaint of urinary frequency and/or urge incontinence were studied. We applied 15 Hz. repetitive magnetic stimulation of the sacral roots with 50% intensity output for 5 seconds per minute for 30 minutes. Urodynamic investigations during magnetic stimulation were performed in 11 cases to evaluate acute effects for lowering urinary tract function. Another 37 women were enrolled in a placebo controlled study to investigate short-term effects. The mean number of voids daily, mean urine volume per void, number of leaks for 3 days and quality of life score were evaluated before and 1 week after stimulation.

RESULTS

Urodynamic investigations revealed apparent elevation in mean maximum urethral closure pressure plus or minus standard deviation during stimulation in all 11 cases (8.4 +/- 3.6 cm. water, p = 0.00001) and a significant increase in mean bladder capacity after stimulation (58.2 +/- 50.2 ml., p = 0.003). In the placebo controlled study all parameters significantly improved in the active stimulation group. Intergroup comparison showed that mean urine volume per void, mean number of leaks and mean quality of life score improved more significantly in the active than in the sham stimulation group (23.5 +/- 25.6 ml. versus 6.2 +/- 22.5, p = 0.04, 3.6 +/- 4.1 versus 0.4 +/- 1.4, p = 0.04 and 1.4 +/- 1.3 versus 0.4 +/- 0.8, p = 0.01, respectively). No adverse effects were noted in any patients.

CONCLUSIONS

These results suggest that magnetic stimulation of the sacral roots may be useful for treating urinary frequency and urge incontinence.

Sacral neuromodulation for the treatment of bladder dysfunction

S3 nerve root neuromodulation is becoming an accepted therapy for individuals afflicted with lower urinary tract symptoms, such as idiopathic urinary urge incontinence, frequency, urgency, and urinary retention, who fail current standard therapies. This patient population is difficult to treat, and this therapy offers an option that can restore quality of life to these individuals. While the precise pathophysiologic mechanisms underlying these voiding symptoms is unknown based on the physiology of bladder function, it is logical to conclude that they relate to some aberration of the neuromuscular apparatus of the bladder and/or its outlet (the urethra). These pathophysiologic defects are not overtly manifested outside the lower urinary tract because these patients routinely do not have any apparent neurologic deficits. The fact that S3 neuromodulation can clinically improve these lower urinary tract symptoms would support the notion that the neural regulation of the bladder is somehow altered in these patients. This paper presents a review of the current knowledge regarding sacral neuromodulation in treatment of non-neurogenic voiding dysfunction.

Sacral nerve neuromodulation in the treatment of refractory motor urge incontinence

Sacral nerve neuromodulation may be an effective treatment option in patients with motor urge incontinence when conservative therapy fails. The effect of treatment is durable in the majority of patients, but there is also a high failure rate. The cause of failure remains unclear in most cases as it is still unknown exactly how neuromodulation works. The present review summarizes the results of patient treatment and research into the working mechanism of neuromodulation, as well as the technical developments described in the past year.