Neurourology and Urodynamics 27:779–781 (2008)

Unilateral Versus Bilateral Stage I Neuromodulator LeadPlacement for the Treatment of Refractory

Voiding Dysfunction

Khanh Pham, Michael L. Guralnick, and R. Corey O’Connor*Department of Urology, Medical College of Wisconsin, Milwaukee, Wisconsin

Aims: To determine if bilateral S3 lead placement during the stage I trial period improves the ‘‘success’’ rate foradvancing to stage II (permanent) sacral neuromodulator placement. Methods: A retrospective chart review of 124(20 male and 104 female) patients undergoing stage I sacral neuromodulation (InterStim1, Medtronic, Minneapolis,Minnesota) implantation for the treatment of refractory voiding dysfunction was performed. Patients were dividedinto two cohorts based on unilateral versus bilateral stage I lead placement in the S3 foramina. Both groups werethen evaluated and compared with regards to overall ‘‘success’’, defined as progression from stage I to stage IIplacement. Results: Fifty-five (44%) patients underwent unilateral stage I lead placement and 69 (56%) receivedbilateral S3 leads. Successful stage I trials were reported in 32/55 (58%) and 53/69 (76%) of unilateral and bilateralcohorts, respectively (P ¼ 0.03). Five wound infections were reported—2 (3.6%) following unilateral and 3 (4.3%)after bilateral stage I lead placement. No other complications were encountered. Conclusions: Bilateral stage Ineuromodulation trial provides a significantly higher rate of improvement in refractory voiding symptoms to allowfor the progress to stage II implantation. Neurourol. Urodynam. 27:779–781, 2008. � 2008 Wiley-Liss, Inc.

Key words: bilateral; neuromodulation; voiding dysfunction

INTRODUCTION

Over the past decade sacral neuromodulation has becomea viable option for the treatment of refractory urinaryurgency/frequency and non-obstructive urinary retention.While the exact mechanism of action remains unclear, mosttheories involve the modulation of afferent and/or efferentneural pathways of the bladder.1 Published success rates forall approved uses range from 40% to 80%.2–6

Common practice involves staged implantation of thesacral neurostimulator. Stage I entails percutaneous place-ment of a quadripolar tined lead into the right or left thirdsacral (S3) foramina under fluoroscopic guidance.4 A trialperiod of lead stimulation via an external power source is thenconducted for 1–3 weeks to assess efficacy. Stage II involvesthe subcutaneous placement of an implantable pulse gene-rator in the patient’s lower back or abdomen which isconnected to the previously placed tined lead. Progressionfrom stage I to stage II is warranted if the patient experiencesa greater than 50% improvement in urinary symptoms duringthe trial stimulation period. Generally, a unilateral S3 lead isplaced during the stage I phase to assess for efficacy. In ourpractice we have begun placing bilateral S3 leads duringstage I. The leads are stimulated separately during the trialphase to determine which side results in the greatest degreeof symptomatic improvement. To our knowledge, no studyhas specifically examined the efficacy of unilateral versusbilateral stage I lead placement. As a result, we retrospectivelycompared the outcomes of patients following unilateralversus bilateral stage I lead placement for the treatmentof refractory urinary urgency/frequency, non-obstructiveurinary retention or chronic pelvic pain.

MATERIALS AND METHODS

Following local institutional review board approval medicalrecords of all patients undergoing stage I sacral neurostimulator

(InterStim1, Medtronic, Minneapolis, MN) implantation for thetreatment of refractory voiding dysfunction from October 2001to June 2007 were retrospectively reviewed. Prior to surgeryeach patient underwent thorough urological history, physicalexamination, urine analysis and urodynamic testing. Cysto-scopic evaluation and urine cytology were performed onpatients with hematuria to rule out malignancy or foreignbody as a cause of irritative voiding symptoms.

Patients were divided into two cohorts based on unilateralversus bilateral stage I lead placement in the third sacralforamina. The decision to perform unilateral or bilateralplacement was determined by surgeon discretion. Patientsin the bilateral cohort had each lead tested separatelyduring the trial period to determine which, if any, workedbetter. Patients that underwent successful unilateral orbilateral stage I lead placement proceeded to unilateral stageII implantation. The S3 lead that was not utilized was removedat the time of stage II implantation. Progression from stage I tostage II was performed for all patients that exhibited greaterthan 50% improvement in urinary symptoms during a 2-weektrial period, based on subjective (symptom scores) andobjective (diaries and pad weight tests) measures. Patientsthat did not report a 50% improvement in symptomatologyfollowing stage I implantation underwent removal of allcomponents. Information abstracted from medical recordsincluded indications for neuromodulation trial, lead loca-tion(s), progression from stage I to II and complications.Any patient with who developed lead infection had the

No conflict of interest reported by the author(s).Dirk de Ridder led the review process.*Correspondence to: R. Corey O’Connor, MD, Assistant Professor of Urology,Department of Urology, Medical College of Wisconsin, 9200 W. WisconsinAvenue, Milwaukee, WI 53226. E-mail: coreyoc@aol.comReceived 19 December 2007; Accepted 23 January 2008Published online 12 June 2008 in Wiley InterScience(www.interscience.wiley.com)DOI 10.1002/nau.20577

� 2008 Wiley-Liss, Inc.

components explanted and was not considered ‘‘successful.’’The primary outcome measure for this study was progressionto stage II. Statistical significance was determined usingFisher’s exact test.

RESULTS

One-hundred twenty-four (20 male and 104 female)patients underwent stage I sacral neuromodulator implanta-tion. Fifty-five (44%) received unilateral and 69 (56%) bilateralS3 leads. Mean age of the unilateral group was 51.8 yearswhile those receiving bilateral leads averaged 49.9 years(P ¼ 0.53). Indications for the procedure are listed in Table I.Pre-existing chronic co-morbidities were statistically similarfor each group (Table II). Successful stage I trials were reportedin 32/55 (58%) and 53/69 (76%) of unilateral and bilateralcohorts, respectively (P ¼ 0.03) (Table III). When examinedbased on indications for sacral simulation, patients under-going bilateral lead placement for urinary urgency/frequencydemonstrated a significantly higher success rate than theunilateral lead patients (P ¼ 0.04). Subjects receiving bilateralimplants for urinary retention or pelvic pain did notdemonstrate a significantly improved outcome when com-pared to the unilateral cohort.

Five wound infections were reported—two (3.6%) followingunilateral and three (4.3%) after bilateral stage I lead place-ment. No other complications were encountered.

DISCUSSION

Sacral nerve stimulation is an efficacious treatment forpatients with refractory voiding dysfunction, namelyurgency/frequency or non-obstructive urinary retention.Typically, the stage I sacral neuromodulation trial involvesthe percutaneous placement of a tined lead into the right orleft S3 foramina. We began placing bilateral leads during stageI with the belief that by testing both the right and leftforaminae it would improve the likelihood that at least oneside would provide symptom relief and increase the pro-gression rate to stage II. Previously published reports indicatesuccessful staged implantation rates ranging from 40% to 80%depending on indication.2–6 In our study, successful unilateraltrial stimulation was reported in 58% of patients. Success ratesimproved to 76% in the bilateral group (P ¼ 0.04). Our resultsdo suggest that when bilateral leads are implanted and testedseparately, there is a greater likelihood of symptomaticimprovement with resultant progression to stage II pulsegenerator implantation. This was particularly true for oururgency/frequency patients but not for patients undergoingthe procedure for urinary retention or pelvic pain patients.However, the population of patients in the latter two groupsmay be too small to determine statistical meaning.

To date, one clinical publication has been performed thatexamined the use of unilateral versus bilateral stimulation.A prospective randomized crossover study by Scheepens et al.reported the outcomes of 33 patients that received either

unilateral or bilateral sacral stimulation. The results showedno statistically significant difference in voiding symptomsbetween the two groups.7 As a result, bilateral neuromodula-tion was not routinely recommended. The major differencebetween Scheepens’ findings and our study is that we didnot perform bilateral simultaneous stimulation. Instead, weplaced bilateral S3 electrodes but stimulated each separatelyin the hope of determining which side produced the greatestsymptomatic improvement.

Limitations of bilateral stage I lead placement includeincreased cost and operative time. The additional hardwarecost of bilateral lead insertion is approximately $1500 whencompared to placement of a single lead. While opera-tive times can vary, in our experience the bilateral stage Iprocedure takes approximately 20–30 additional minuteswhen compared to conventional, unilateral lead placement.Furthermore, with the added hardware being implanted,one could hypothesize a higher risk for device infection.Device infection after sacral modulator implantation has beenreported in up to 12% of patients.8 Based on the currentstudy, however, it does not appear that bilateral lead place-ment increases the risk for wound infection or complication.Individual surgeons should decide if the increased opera-tive time and cost balances improved patient outcomes.

Although our study is retrospective, both unilateral andbilateral lead groups appear to be equal with regard to age,indication for sacral neuromodulation and co-existing chronicdiseases. Amundsen et al.9 published that success ratesfollowing sacral neuromodulation are decreased in patientsolder than 55 and/or with more than three chronic medicalconditions. Despite the fact that many of the patients in ourstudy fulfilled these negative prognostic criteria, the distribu-tion of these individuals between each cohort appeared to beequal. A prospective, randomized trial would be ideal tofurther examine the outcomes. Alternatively, patients that failunilateral stage I lead placement could undergo contralaterallead placement to determine if a significant success ratewould be noted.

CONCLUSIONS

Sacral neuromodulation is a successful treatment modalityfor refractory urinary urgency/frequency and non-obstructive

Neurourology and Urodynamics DOI 10.1002/nau

TABLE I. Indications for Sacral Neurostimulator Trial

UnilateralS3 lead

placement (%)

BilateralS3 lead

placement (%) P value

Urinary urgency/frequency 40 (73) 55 (80) 0.40

Non-obstructive urinary retention 14 (25) 13 (19) 0.39

Pelvic pain 1 (2) 1 (2) 0.94

Total 55 69

TABLE II. Pre-Existing Chronic Co-Morbidities

Chronicco-morbidities

Unilateral(n ¼ 55) S3 leadplacement (%)

Bilateral(n ¼ 69) S3 leadplacement (%) P value

Cardiac 22 (40) 22 (32) 0.45

Pulmonary 13 (24) 17 (25) 0.9

Gastrointestinal 20 (36) 22 (32) 0.7

Pelvic 18 (33) 28 (41) 0.45

Neurologic 22 (40) 23 (33) 0.46

Psychiatric 6 (11) 9 (13) 0.79

Rheumatologic 12 (22) 10 (14) 0.35

Endocrine 13 (24) 11 (16) 0.36

TABLE III. Outcomes Following Stage I Implantation

Successfulunilateral

trial (%)

Successfulbilateraltrial (%) P value

Overall 32/55 (58) 53/69 (77) 0.03

Urgency/frequency 24/40 (60) 44/55 (80) 0.04

Non-obstructive urinary retention 8/14 (57) 8/13 (62) 0.92

Pelvic pain 0/1 (0) 1/1 (100)

780 Pham et al.

urinary retention. Based on our retrospective review, patientsreceiving bilateral stage I S3 leads demonstrated significantlyimproved outcomes when compared to unilaterally placedleads. Therefore, surgeons may consider bilateral percuta-neous lead placement when performing stage I neuromodu-lation for refractory voiding dysfunction. Randomized,prospective clinical trials may be warranted to fully determinethe benefit of bilateral stage I lead placement.

REFERENCES

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2. van Kerrebroeck EV, Scheepens WA, de Bie RA, et al. European experience withbilateral sacral neuromodulation in patients with chronic lower urinary tractdysfunction. Urol Clin North Am 2005;32:51–7.

3. Siegel SW, Catanzaro F, Dijkema HE, et al. Long-term results of a multicenterstudy on sacral nerve stimulation for treatment of urinary urge incontinence,urgency-frequency, and retention. Urology 2000;56:87–91.

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5. Scheepens WA, Van Koeveringe GA, de Bie RA, et al. Long-term efficacy andsafety results of the two-stage implantation technique in sacral neuro-modulation. BJU Int 2002;90:840–5.

6. van Kerrebroeck PE, van Voskuilen AC, Heesakkers JP, et al. Results of sacralneuromodulation therapy for urinary voiding dysfunction: Outcomes of aprospective, worldwide clinical study. J Urol 2007;178:2029–34.

7. Scheepens WA, de Bie RA, Weil EH, et al. Unilateral versus bilateral sacralneuromodulation in patients with chronic lower urinary tract dysfunction.J Urol 2002;168:2046–50.

8. Guralnick ML, Benouni S, O’Connor RC, et al. Characteristics of infections inpatients undergoing staged implantation for sacral nerve stimulation.Urology 2007;69:1073–6.

9. Amundsen DL, Romero AA, Jamison MG, et al. Sacral neuromodulationfor intractable urge incontinence: Are there factors associated with cure?Urology 2005;66:746–50.

Neurourology and Urodynamics DOI 10.1002/nau

Unilateral Versus Bilateral Lead Placement 781