Overactive bladder (OAB) has detrimental effects on quality of life, and patients often exhaust non-surgical treatment options with minimal improvement in their symptoms. Sacral neuromodulation is a third line, USA FDA approved therapy for drug-resistant OAB. We evaluated clinical and procedural characteristics of sacral neuromodulation that predict short-term and long-term efficacy

A retrospective chart review was performed on patients who underwent a staged sacral neuromodulation procedure between January 1, 2007 and January 1, 2018. The clinical and procedural characteristics we evaluated include BMI, comorbidities, age, intraoperative motor responses, and operative time. Endpoints included placement of implantable pulse generator (IPG), tined lead revision, and patient reported clinical responses (defined as > 50% symptom improvement from baseline) at various time points after IPG implant.  Intraoperative motor responses were analyzed, and patients were divided into two groups.  Group 1 had anal bellows and great toe dorsiflexion in <4 electrodes, and group 2 had anal bellows and great toe dorsiflexion in all 4 electrodes.  Using SAS 9.4, we performed descriptive statistics to calculate mean and standard deviation for continuous variables and frequency and percentage for categorical variables. The Mann-Whitney U test was used to compare mean differences, and the Chi-square test was used to compare percentage differences between the two groups with different electrode responses.

We performed a retrospective analysis of 196 female OAB subjects with a mean age of 62.5 years (SD +/-14.3). Mean operative time for stage 1 was 72.9 minutes (SD +/- 21.1), and 72% had prior pelvic surgery. The mean BMI was 31 (SD +/- 7.5).  As shown in Figure 1, 91.7% of the patients had a successful Stage 1 trial of sacral neuromodulation, and 83% of these patients reported success at their first appointment after IPG placement. Furthermore, 71% reported continued success at their 3-6 month follow-up. Yet, 27% required tined lead revision for either lack of efficacy, pain, and/or infection.  As shown in Figure 2, those patients previously treated with onabotulinumtoxinA or pelvic floor physical therapy were less likely to go onto Stage 2 sacral neuromodulation IPG placement (p<0.047) or report success postoperatively (p<0.010). Age >65 years at the time of IPG placement was associated with higher rates of lead revision (p<0.039) and device explantation (p< 0.011).  The two groups with different electrode responses were analyzed.  There was no statistically significant difference between these 2 groups in the rates of successful Stage 1 sacral neuromodulation trial, self-reported success, or lead revision.

Patients were less likely to have success if they were >65 years of age.  The ROSETTA predictors study also found greater patient age to be associated with less reduction in urgency urinary incontinence episodes per day in patients undergoing staged sacral neuromodulation implant [1].  Additionally, patients previously treated with onabotulinumtoxinA or pelvic floor physical therapy were less likely to have success with sacral neuromodulation.  We are currently looking at factors in both of these groups (such as advanced voiding dysfunction) that may explain the lower success rates seen in patients that underwent sacral neuromodulation after prior onabotulinumtoxinA or pelvic physical therapy.  In addition, we found that patients with anal bellows and great toe dorsiflexion in <4 electrodes during intra-operative tined lead testing did not have reduced short or long-term success.  Although we strive to achieve appropriate motor and/or sensory responses on all 4 electrodes at stimulus amplitudes of <2 V as recommended in the ICS best practice statement for the use of sacral neuromodulation [2], it has been shown that leads that offer responses at fewer than 4 electrodes can be successful [3].  Finally, a limitation of this study is that not all patients completed standardized symptom bother questionnaires such as the Urogenital Distress Inventory 6 (UDI-6), the Incontinence Impact Questionnaire short form (IIQ-7), and the Overactive Bladder questionnaire (OAB-q).

Sacral neuromodulation is a well-established treatment for refractory OAB.  In this retrospective study of 196 women with drug-resistant OAB, we found that factors associated with failure to complete stage 2 IPG implant included patient age >65, previous onabotulinumtoxinA treatment, and previous pelvic floor physical therapy.  Neither short nor long-term success was impacted by having anal bellows and great toe dorsiflexion in <4 electrodes during the intra-operative testing of the tined lead.

Richter HE, Amundsen CL, Erickson SW, Jelovsek JE, Komesu Y, Chermansky C, et al. Characteristics Associated with Treatment Response and Satisfaction in Women Undergoing OnabotulinumtoxinA and Sacral Neuromodulation for Refractory Urgency Urinary Incontinence. J Urol. 2017;198(4):890-6.
Goldman HB, Lloyd JC, Noblett KL, and Siegel SW. International Continence Society best practice statement for use of sacral neuromodulation. Neurourol Urodyn. 2018;37:1823-48.
Gilleran JP, Killinger K, Boura J, and Peters KM.  Number of Active Electrodes at Time of Staged Tined Lead Interstim Implant Does Not Impact Clinical Outcomes. Neurourol Urodyn. 2016;35:625-629.