Login to Access Video or Poster Abstract: MP85-19
Sources of Funding: none

Introduction

Sacral neuromodulation with InterstimTM (Medtronic) is a highly successful treatment for both non-obstructive urinary retention as well as for overactive bladder (OAB) symptoms, but the mechanism of action is not yet defined. Importantly, attempts to predict and improve outcomes have been inconsistent. In this study we assessed the association between laterality of lead placement and patient asymmetry. We have recognized patterns of asymmetry in our patients with severe voiding symptoms. We hypothesize a higher success with lead placement on the less formed side.

Methods

We performed an IRB approved retrospective chart review of InterstimTM placements from 2003 to 2013. A total of 57 patients were identified, and who had undergone first-stage lead placement for non-obstructive urinary retention or OAB._x000D_ Patient symmetry was assessed by preoperative physical examination findings of bilateral sacral sensory function, gluteal muscle mass, intrinsic muscles of the feet, and pelvic floor muscle strength. Asymmetry was defined as a significant, consistent lateralized difference in findings based on one observer. Among asymmetric patients the side determined to have diminished function was deemed less versatile. Subtle findings were considered symmetric. Successful lead placement was regarded as a 50% or greater improvement in urinary symptoms and transition to second stage InterstimTM placement._x000D_

Results

Of the 57 patients reviewed, 47 (82%) progressed to successful second stage InterStimTM placement while 10 (18%) failed. A majority, 39/57(67%) of patients were deemed asymmetric and of these 33 (84%) progressed to second stage. Of the 18 symmetric patients success was achieved in 14 (78%). In a subgroup analysis of 19 asymmetric patients who underwent an initial trial of bilateral lead placements, 13 reported greater benefit with the lead placed on the less versatile side, 2 were equivocal, and only 4 favored the more versatile side (p=0.003).

Conclusions

Asymmetry is a very frequent finding in patients with pelvic floor dysfunction. Lead placement on the less versatile side of asymmetric patients correlated with better InterstimTM success. Determination of asymmetry among InterStimTM candidates should be considered during preoperative evaluation to guide the choice of side for lead placement.

Funding

none