How sacral nerve stimulation neuromodulation works

Advances in the role of sacral nerve neuromodulation in lower urinary tract symptoms

Sacral neuromodulation has been developed to treat chronic lower urinary tract symptoms, resistant to classical conservative therapy. The suspected mechanisms of action include afferent stimulation of the central nervous system and modulation of activity at the level of the brain. Typical neuromodulation is indicated both in overactivity and in underactivity of the lower urinary tract. In the majority of patients, a unilateral electrode in a sacral foramen and connected to a pulse generator is sufficient to achieve significant clinical results also on long term. In recent years, other urological indications have been explored.

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.

Expanding the Role of Neuromodulation for Overactive Bladder: New Indications and Alternatives to Delivery

From the time that it was granted US Food and Drug Administration approval, neuromodulation has secured a firm position in the treatment algorithm for overactive bladder. With neuromodulation, physicians were able to bridge the gap between the two ends of the treatment spectrum (medical therapy and open surgery). Sacral nerve stimulation has been the most widely used form of neuromodulation. Recent modifications to its design, namely the development of the tined lead and the launching of the refined InterStim II (Medtronic, Minneapolis, MN), have made sacral nerve simulation even less invasive and more effective. While InterStim is maintaining a level of success with these advancements, peripheral means of neuromodulation are being explored. The current literature takes a closer look at posterior tibial and pudendal nerve stimulation as alternatives to sacral nerve stimulation. The field of neuromodulation is also expanding in terms of the target patient population, as it is being used to treat children, patients with neurological disease, and others. As the role of neuromodulation increases, we must continue to assess its efficacy, safety, and cost-effectiveness in comparison to other therapeutic options.

Quantification of neurological and other contributors to continence in female rats

Smooth muscle, striated muscle, their central and peripheral innervations and control, and mucosal coaptation contribute to maintenance of continence. We used manual leak point pressure (mLPP) testing and electrical stimulation LPP (eLPP) testing in female rats to quantify the contribution of these factors to urethral resistance, a measure of continence. Abdominal muscles were electrically stimulated to induce leakage for eLPP. A Crede maneuver was applied for mLPP. These were repeated after complete T8 spinal cord injury (SCI) and/or bilateral pudendal nerve transection (PNT). After euthanasia, mLPP was repeated. MLPP was not significantly affected by opening the abdomen, suggesting that intra-abdominal pressure transmission contributes little to continence during slow pressure changes. ELPP was significantly higher than mLPP in intact rats, after PNT, and after SCI+PNT, suggesting that abdominal pressure transmission contributes to continence during rapid increases in intra-abdominal pressure. MLPP decreased significantly after PNT, indicating that urethral striated muscles contribute significantly to continence. ELPP decreased significantly after PNT with and without SCI, suggesting that supraspinal control significantly affects continence during rapid pressure changes, but not during slow pressure changes. MLPP after euthanasia was significantly decreased compared to mLPP after SCI+PNT, suggesting that urethral mucosal seal coaptation and tissue elasticity also contribute to continence. The urethra is a complex organ that maintains continence via a highly organized and hierarchical system involving both the central and peripheral nervous systems.

Clinical concomitant benefits on pelvic floor dysfunctions after sacral neuromodulation in patients with incomplete spinal cord injury

OBJECTIVES

To assess the concomitant clinical improvement in incomplete spinal cord injury patients (SCIPs) suffering from neurogenic bowel symptoms (NBSs), neurogenic lower urinary tract symptoms (NLUTSs) and neurogenic erectile dysfunction (NED) using sacral neuromodulation (SNM) for NBSs and NLUTSs.

METHODS

Seventy-five SCIPs were selected. Before and during the follow-ups post-SNM, NLUTSs and NBSs were detected mainly through specific diaries. Erectile function was assessed using the International Index of Erectile Function composed of 5 questions (IIEF5). Quality of life (QoL) was measured with the Short Form 36 Health Survey questionnaire (SF-36). During the first stage, in which a permanent electrode was inserted percutaneously into the third sacral foramina and stimulated using an external generator, patients with NBSs or NLUTSs were required to improve their symptoms by at least 50% compared with baseline before proceeding to the second stage in which the generator was placed in the patient's buttock. NED patients needed to increase their IIEF5 score by at least 25% compared with baseline (evaluated initially 3 months after the second stage) in order to continue follow-up.

RESULTS

Fourteen out of 37 subjects who manifested two functional pelvic dysfunctions at baseline maintained notable clinical improvement in two pelvic functions (median follow-up >3 years). Six had non-obstructive retention (NOR) and NED, six double incontinence, and two constipation with NOR. In the general and mental health domains of the SF-36, all patients improved their scores by at least 20% compared with baseline.

CONCLUSIONS

SNM may be beneficial to selected incomplete SCIP with concomitant pelvic functional disturbances.

Long-term outcome and surgical interventions after sacral neuromodulation implant for lower urinary tract symptoms: 14-year experience at 1 center

PURPOSE

Few reports address the reoperation rate after sacral neuromodulation implants. We report our long-term results and reoperations during our 14-year experience with sacral neuromodulation at our center.

MATERIALS AND METHODS

We retrospectively reviewed the patient database at our center to assess the long-term outcome, incidence and cause of surgical re-intervention after InterStim® sacral neuromodulation implantation for lower urinary tract dysfunction between 1994 and 2008.

RESULTS

A total of 96 sacral neuromodulation devices were implanted in 88 women and 8 men. Indications for implantation were bladder pain syndrome in 47.9% of cases, urgency urinary incontinence in 35.4% and idiopathic urinary retention in 16.7%. The explantation rate was 20.8% and median time to removal was 18.5 months. Reasons for explantation in all subgroups were poor result in 12 patients, painful stimulation in 6 and radiation of stimulation to the leg in 2. Median long-term followup was 50.7 months. The long-term success rate was 87.5%, 84.8% and 73% in patients with idiopathic urinary retention, urgency urinary incontinence and bladder pain syndrome, respectively. Overall 39% of patients needed revision of the sacral neuromodulation implant. The main reason for revision was loss of stimulation in 58.5% of cases. The revision rate decreased with the introduction of the tined lead technique from 50% using lead Model 3092 to 31% using lead Model 3893 (Medtronic, Minneapolis, Minnesota). The battery was changed in 8 patients. Mean battery life was 101.8 months.

CONCLUSIONS

Sacral neuromodulation is a minimally invasive procedure with a good long-term outcome. The reoperation rate has improved with advances in surgical technique and equipment.

Reduced somatosensory cortical activation in experimental models of neuropathic fecal incontinence

PURPOSE

Alteration in cortical awareness may be the underlying abnormality in patients with neuropathic fecal incontinence. The cortical effects of inferior rectal nerve injury were determined using somatosensory evoked cortical potential recordings in an experimental model of neuropathic fecal incontinence.

METHODS

Eighteen female virgin Wistar rats were assigned equally to one of three groups: an unoperated control group, a nerve crush group (positive control), and a nerve balloon compression group. Four weeks following the injury, all animals underwent somatosensory evoked cortical potential recordings. Following this, the inferior rectal nerve was harvested, resin-embedded, sectioned (1 microm thickness), and axonal counts and axonal cross-sectional areas were analyzed using Scion Image software.

RESULTS

Somatosensory evoked cortical potentials were reduced in the nerve crush and balloon compression groups compared with controls (P = 0.024, P = 0.03, respectively). The inferior rectal nerve was harvested in 14 of the 18 animals (4 control, 5 nerve crush, 5 balloon compression). There were no differences in median inferior rectal nerve total axonal counts (P = 0.69) or in the frequency distribution of axonal cross-sectional area between groups (control vs. nerve crush and control vs. balloon compression: P = 0.92, P = 0.17, respectively).

CONCLUSIONS

Somatosensory evoked cortical potential amplitude is reduced following crush or compression injury to the inferior rectal nerve. In neuropathic fecal incontinence, alteration in cortical awareness may be the result of processing modification at a central and not peripheral level.

A Dual Benefit of Sacral Neuromodulation

Sacral neuromodulation is a therapeutic option for women with detrusor overactivity and more recently has been used in patients with fecal incontinence and slow-transit constipation. A 47-year-old woman presented with chronic constipation since childhood. She used multiple laxatives, fiber supplements, and enemas, all without success, and defecated only once per week. Extensive investigations, including barium enema, colonoscopy, defecating proctography, pelvic magnetic resonance imaging, and anorectal manometry all were normal. A transit study showed delayed small-bowel emptying. Colonic transit could not be accurately interpreted because of the marked delayed in proximal transit. An ileostomy was being considered to defunction the colon after the patient become desperate for a better quality of life. She also complained of severe urinary frequency and incomplete emptying. A cystoscopy was normal, and a temporary sacral neuromodulation device was inserted as a staged procedure to improve her urinary symptoms. From the day of device placement and thereafter, the patient defecated without difficulty and has also been free of bladder symptoms. Repeat colonic transit has shown normalization of the stomach, small bowel, and colon.

Neuromodulation techniques: a comparison of available and new therapies

Neuromodulation has become ever more common in the fields of urology and voiding dysfunction. Many therapeutic alternatives have emerged to increase effectiveness of these therapies and reduce morbidity and invasiveness. Each new modality needs to prove its efficacy in common indications for voiding dysfunction such as refractory urgency-frequency, urge incontinence, and perhaps urinary retention, as well as in select patient populations and subgroups. We need more information to broaden the applicability of neuromodulation to larger numbers of patients and conditions.

Current and future techniques of neuromodulation for bladder dysfunction

Recent increase in the use of neuromodulation for the treatment of urinary urgency and frequency, urge incontinence, and nonobstructive urinary retention has coincided with improved knowledge of micturition physiology and concurrent technologic advances in nerve stimulation. Currently, the most common technology for bladder neuromodulation involves stimulation through the S3 foramen, or sacral neuromodulation, although other techniques of neuromodulation continue to be explored. Despite many advances in neuromodulation, the exact mechanism of action remains uncertain. Additionally, which patients will respond to neuromodulation remains unclear, and although there is a standard method for testing, this procedure is invasive and expensive. As we continue to improve patient selection criteria and better understand the mechanism of action, the efficacy and patient satisfaction should continue to increase. Currently, most patients considered for implantation with a neuromodulator are those unresponsive to other conservative treatments for bladder dysfunction.

Sacral nerve stimulation: neuromodulation for voiding dysfunction and pain

Voiding dysfunction, which includes incontinence, retention, and chronic pelvic pain, is a relatively frequent problem that can be difficult to manage. Neuromodulation via stimulation of the sacral nerves has been shown to improve these symptoms, although the exact mechanisms remain elusive. Techniques for nerve stimulation may vary, depending on the disease, location of pain, and the patient's anatomy. In addition to placement of electrodes on the sacral nerve roots, modulation has also been reported by peripheral branches of the sacral nerves including the pudendal and posterior tibial nerves. Newer surgical techniques have significantly decreased the morbidity of the procedures and increased the probability of a successful outcome.

Sacral neuromodulation in the older woman

In the last 10 years, sacral neuromodulation has evolved from an experimental therapy to a safe and proven treatment option for patients with a variety of complex lower urinary tract disorders. It is currently Food and Drug Administration approved for the following indications: intractable urge incontinence, urgency-frequency, and nonobstructive urinary retention. Herein, we will discuss some of the factors complicating incontinence treatment in the elderly population paying particular attention to sacral neuromodulation, its history, indications, and applications within the elderly female population.

Refractory overactive bladder after urethrolysis for bladder outlet obstruction: management with sacral neuromodulation

Refractory overactive bladder (OAB) after urethrolysis for iatrogenic bladder outlet obstruction (BOO) is a clinical dilemma without established guidelines for management. We sought to evaluate the efficacy of sacral neuromodulation (SNM) in the management of this complex patient population. Retrospective review identified eight patients who underwent SNM secondary to refractory OAB after urethrolysis or sling take-down. SNM was performed with the Interstim device (Medtronic, Minneapolis) using a two-stage implant technique. SNM outcomes were determined subjectively during follow-up. Validated questionnaires were completed to assess symptom bother, patient satisfaction, and quality of life. Statistical analyses were conducted using Stata version 9.0. Six patients had a favorable response to SNM during test stimulation and underwent implantation of the implantable pulse generator (IPG). With follow-up of 15.7 +/- 11.1 months (6-34), all patients significantly improved, with three patients being dry and three patients having one to two urgency incontinence episodes per week. Patient-reported outcomes indicated that patients perceived themselves as very much improved (3) or much improved (3) after SNM, while those failing test stimulation perceived no change. Quality of life and symptom bother were significantly better in SNM responders vs nonresponders. SNM appears to be an effective and viable treatment option in this complex patient population. Further work is needed to determine clinical factors predictive of outcome and durability of response.

Bilateral Caudal Epidural Neuromodulation for Refractory Urinary Retention: A Salvage Procedure

PURPOSE

Sacral neuromodulation with InterStim is approved for idiopathic urinary retention with a success rate of approximately 69%. To our knowledge currently no alternatives exist for patients in whom S3 neuromodulation fails. We report a new technique and our experience with bilateral caudal epidural neuromodulation in patients in urinary retention in whom unilateral or bilateral S3 InterStim failed.

MATERIALS AND METHODS

Eight patients with multifactorial urinary retention in whom S3 InterStim previously failed underwent retrograde placement of bilateral tined leads into the caudal epidural space for sacral nerve stimulation. Patients with a 50% or greater clinical response underwent stage 2 Synergy-Versitrel implantable pulse generator placement. Patients were evaluated with voiding diaries, the Urinary Distress Inventory Questionnaire short form, quality of life assessment, need for catheterization and post-void residual urine preoperatively, and 6 months after implantation.

RESULTS

Five of the 8 patients experienced return of micturition and underwent placement of a permanent implantable pulse generator. At 6-month followup 4 of the 5 patients voided to completion. One patient improved more than 50% and now catheterizes once daily with a post-void residual urine of 200 cc. There was a significant decrease in obstructive symptoms on the Urinary Distress Inventory Questionnaire short form and improved overall quality of life.

CONCLUSIONS

To our knowledge this is the first report of the use of bilateral caudal epidural neuromodulation for refractory urinary retention. This therapy can be successful in patients in whom prior InterStim therapy failed.

Sacral neuromodulation for nonobstructive urinary retention--is success predictable?

PURPOSE

We investigated whether there are factors which can predict successful stage II (permanent) sacral nerve stimulator (InterStim) implantation for patients with nonobstructive urinary retention.

MATERIALS AND METHODS

We retrospectively reviewed our sacral neuromodulation database from January 1, 1999 to January 1, 2006. A total of 29 patients were referred to the William Beaumont Hospital Department of Urology for nonobstructive urinary retention. All patients completed a 3-day voiding log followed by test stimulation. Patients underwent test stimulation for a 2-week trial period. Those who experienced 50% improvement in void volume and/or catheterization frequency subsequently underwent permanent implantation. We reviewed patient charts with respect to age, sex, duration of retention, underlying diagnosis for retention and voiding ability.

RESULTS

Of the 29 patients 15 were men and 14 were women. Mean patient age was 58.8+/-16 years (range 18 to 82). The mean age of the men in the study was 55.5+/-18 years while the mean age of the women was 62.3+/-14 years. Although all the patients performed intermittent self-catheterization 18 were able to void (more than 50 cc per void). The remaining 11 patients had minimal (50 cc or less) or no ability to void. Of the 18 patients who were able to void 12 (67%) underwent successful permanent implantation. However, voiding improved after test stimulation in only 2 of the 11 patients (18%) who had been unable to void. This difference was statistically significant (p=0.02) and suggests that pre-implantation ability to void can predict success of test stimulation.

CONCLUSIONS

Patient ability to void predicts success of first stage test stimulation. Although we would still offer a trial of sacral neuromodulation to those with nonobstructive urinary retention and the inability to void, this study would allow better counseling regarding the likelihood of successful outcome.

Electrical stimulation of sacral dermatomes in multiple sclerosis patients with neurogenic detrusor overactivity

AIMS

Transcutaneous electrical stimulation of the dorsal penile/clitoral nerve (DPN) has been shown to suppress detrusor contractions in patients with neurogenic detrusor overactivity (NDO). However, the long-term use of surface electrodes in the genital region may not be well tolerated and may introduce hygienic challenges. The aim of this study was to assess whether electrical stimulation of the sacral dermatomes could suppress detrusor contractions in multiple sclerosis (MS) patients with NDO, hereby providing an alternative to DPN stimulation.

MATERIALS AND METHODS

A total of 14 MS patients (8 M, 6 F) with low bladder capacity (<300 ml) and a recent urodynamic study showing detrusor overactivity incontinence participated in the study. Three successive slow fill cystometries (16 ml/min) were carried out in each patient. The first filling served as control filling where no stimulation was applied. In the second and third filling electrical stimulation of either the DPN or sacral dermatomes was applied automatically whenever the detrusor pressure exceeded 10 cmH2O.

RESULTS

The control filling showed detrusor overactivity in 12 of the 14 patients. In 10 of the 12 patients one or more detrusor contractions could be suppressed with DPN stimulation. Electrical stimulation of the sacral dermatomes failed to suppress detrusor contractions in all patients.

CONCLUSIONS

Although therapeutic effects may be present from stimulation of the sacral dermatomes, we were unable to demonstrate any acute effects during urodynamics. For this reason stimulation of the sacral dermatomes is not an option in a system that relies on the acute suppression of a detrusor contraction.

Sacral nerve stimulation for neuromodulation of the lower urinary tract

Patients with symptoms of overactive bladder syndrome or non-obstructive urinary retention, refractory to conservative therapy, can nowadays be treated minimally invasively with sacral nerve stimulation (SNS). The use of electric currents to treat urological pathology has a long history but SNS therapy only received FDA approval in 1997. The mechanisms of action are still not known so there are different theories explaining the modulation effect. Recent studies have shown a central modulation effect. Predictive factors which can help to identify the perfect candidates are not known. Over the years the technique of SNS has become less invasive and because of two stage implantation test results have proven to be more reliable. The clinical results for this therapy have proven to be safe and effective and with the technical improvements over the years the re-operation and complication rates have decreased significantly. The clinical results have led to expanding indications because of positive effects in other symptoms. In the field of urology this has resulted in the use of SNS therapy for interstitial cystitis, neurogenic lower urinary dysfunction, and pediatric voiding dysfunction. In the field of gastro-intestinal pathology, SNS therapy is used to treat faecal incontinence and constipation.

Sacral nerve stimulation for the overactive bladder

Pharmacotherapy is the first-line treatment for overactive bladder, but many patients discontinue drug therapy because of intolerable side effects, expense, or lack of longterm adherence. Alternative treatments are needed for patients who are unable to tolerate pharmacotherapy or who do not derive the desired benefits. Sacral nerve stimulation therapy has evolved into one of the most widely accepted treatment modalities in the arena of neurourology. Sacral nerve stimulation activates or "resets" the somatic afferent inputs that play a pivotal role in the modulation of sensory processing for micturition reflex pathways in the spinal cord. This minimally invasive technology offers a safe, reliable, and durable treatment for lower urinary tract dysfunction.

Effects of sacral neuromodulation on female sexual function

The aim of this prospective study was to determine if sacral neuromodulation has an effect on the patient's subsequent sexual function. Sexually active patients that underwent an Interstim Sacroneuromodulator implantation (Medtronic, Minneapolis, MN) for control of bladder symptoms were enrolled. A Female Sexual Function Index (FSFI) was completed before surgery and at a mean of 5.7 months postoperatively. Eleven subjects proceeded to permanent implantation, seven of these were sexually active before and after placement. Three subjects (43%) felt the device impacted on their sexual function in a positive way (1) by decreasing urgency and (2) by increasing desire. Overall sexual frequency increased significantly after the surgery (p=0.047). There were also significant increases in the FSFI total (p=0.002), and domain scores for desire (p=0.004), lubrication (p=0.005), orgasm (p=0.043), satisfaction (p=0.007), and pain (p=0.015). There was no correlation between patient report of urinary symptom improvement and FSFI scores. In conclusion, sacral neuromodulation may improve sexual frequency and sexual function scores in subjects with urgency frequency and urge incontinence.

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.

Predictors of Success for First Stage Neuromodulation: Motor Versus Sensory Response

PURPOSE

We investigated whether intraoperative motor or sensory response is more predictive of successful sacral neuromodulation using the InterStim system.

MATERIALS AND METHODS

A total of 35 patients with medically refractory frequency, urgency and urge incontinence were enrolled in the study. All patients underwent lead placement for quadripolar test stimulation under local anesthesia with intravenous sedation. Confirmation of correct lead placement was by observation of known motor and sensory responses that result from third sacral nerve stimulation. Motor and sensory responses were documented intraoperatively. Patients had a 1-week trial of stimulation, and those who had greater than 50% improvement in symptoms had placement of the implantable pulse generator. Those without at least 50% improvement in their symptoms had the quadripolar lead removed.

RESULTS

Of the 35 patients enrolled 21 had successful quadripolar test stimulation and went on to permanent implantable pulse generator placement. Of the patients who had successful quadripolar test stimulation 95% demonstrated positive intraoperative motor response whereas only 21.4% of patients with unsuccessful quadripolar test stimulation demonstrated positive motor response. If only a positive sensory response was elicited, patients had only a 4.7% chance of having a positive quadripolar test stimulation.

CONCLUSIONS

A positive quadripolar test stimulation (greater than 50% improvement in symptoms) with InterStim sacral neuromodulation is more likely when intraoperative lead placement results in positive motor response vs only sensory response.

Applications of neuromodulation of the lower urinary tract in female urology

Neuromodulation is becoming part of clinical armamentarium for treatment of a variety of lower urinary tract conditions in female urology. Its increased usage stems from need of patients who have exhausted all other therapeutic options for their complex and poorly understood lower urinary tract disorders. Currently neuromodulation may consist of the use of sacral nerve stimulation (SNS) and injectable therapies. Herein, we will discuss the background and development of SNS, its current indications, methods of patient selection and will review the results of the recent published literature on SNS. In addition, we will discuss some of the newer developments in SNS such as Bion device and the future direction in integration of SNS in female urology.

Management of refractory urinary urge incontinence following urogynecological surgery with sacral neuromodulation

AIMS

We sought to explore our patient outcomes utilizing sacral neuromodulation in the management of refractory urinary urge incontinence following urogynecological surgical procedures.

METHODS

A total of 25 women with urinary urge incontinence following urogynecological surgery were selected for SNS therapy and retrospectively analyzed. All patients completed a comprehensive urological evaluation. Clinical data was recorded to determine outcomes and identify parameters that would be predictive of response to neuromodulation. Outcomes were determined via subjective patient questionnaire and graded as follows: significant response (> or =80% improvement), moderate response (> or =50% and <80% improvement), and poor response (<50% response).

RESULTS

Nineteen patients had a previous pubovaginal sling (10 with concomitant pelvic prolapse repair), 3 a previous retropubic suspension, and 3 a transperitoneal vesicovaginal fistula repair. Urethrolysis was performed in 4 patients to alleviate bladder outlet obstruction prior to sacral neuromodulation. Mean patient age was 59.8 years and length of follow-up was 7.2 months. Twenty-two women (88%) had the IPG placed during a Stage 2 procedure. Twenty patients maintained at least a 50% improvement in clinical symptoms at last follow-up and 6 patients were continent. Overall, the number of pads/day improved from 4.2 to 1.1 (P < 0.001). There were no significant differences in response to neuromodulation based upon age, duration of symptoms, type of surgery, or urodynamic parameters.

CONCLUSION

Sacral neuromodulation appears to be an effective therapy in patients with refractory urge incontinence following urogynecological surgery. Larger prospective studies with longer follow-up are needed to assess the durability of this therapeutic modality.