To assess whether the utilisation of a motor response of <3 V during Stage 1 sacral neuromodulation (SNM) results in better clinical outcomes compared to >4 V in patients with overactive bladder (OAB) or urinary retention symptoms.Patients and Methods
An observational, retrospective, double cohort review was conducted of 339 female patients who had experienced medically recalcitrant OAB or urinary retention symptoms. Between September 2001 and September 2014, both cohorts underwent successful Stage 1 to Stage 2 SNM placement. Group A, included 174 women with a motor response at ≤3 V; and Group B, evaluated 110 women with a motor response at ≥4 V for medically recalcitrant OAB. Group C, compared 33 women with a motor response at ≤3 V; and Group D, documented 22 women with a motor response at ≥4 V for non-obstructive urinary retention. Patients completed 3-day voiding diaries, the Urogenital Distress Inventory-6 (UDI-6), Incontinence Impact Questionnaire-7 (IIQ-7), and Patient Global Impression of Improvement Questionnaire.Results
The mean (sd) follow-up was 116.3 (30.3) months in Group A and 112 (34.6) months in Group B (P < 0.354); 150.5 (20.4) months in Group C and 145.8 (17.2) months in Group D (P < 0.38). Successful conversion of Stage 1 to Stage 2 showed statistically significant improvement for both <3-V groups (Groups A and C). Group A had a 93.5% (174/186) conversion rate vs 72.3% (110/152) in Group B for OAB symptoms (P < 0.001). Group C had a 94% (34/36) conversion rate vs 70% (21/30) in Group D (P < 0.017). Defined as a ≥50% reduction in frequency, urgency, urgency incontinence and nocturia, and UDI-6 and IIQ-7 scores, the success rate for Group A was 82.1% (143/174) and for Group B was 63% (69/110) (P < 0.001). The mean battery life improved in both <3-V cohorts (P < 0.001). Annual reprogramming sessions were reduced in Group A and Group C (P < 0.001). Subset analysis of variance showed no statistical improvement in most patient outcomes when 1-V subjects were compared to 2- and 3-V cohorts. However, 32% of 1-V patients (P < 0.001) noted the onset of severe pelvic/perirectal pain and big toe plantar flexion movement with small increments in voltage (0.1–0.2 V) during reprogramming. Only 7% of 2-V and 1% of 3-V patients experienced this complication.Conclusions
Significant improvement was noted (up to 40%) in most clinical voiding parameters in the <3-V patients for both OAB and urinary retention. While <3 V will still statistically improve patient outcomes, a voltage <2 V may elicit self-reprogramming pain with severe bellows and plantar flexion movement, which may discourage patients from therapy adjustments. We recommend randomised, controlled trials to confirm these results.