Abstract: PNFBA-05
Sources of Funding: SUFU Neuromoduation Grant Award

Introduction

Sacral neuromodulation (SNS) with InterStim® is efficacious for the treatment of overactive bladder (OAB); however, its mechanism of action is unclear, and there are no objective markers of response. Prior functional neuroimaging studies have suggested that women with OAB have increased brain activity in the cingulate cortex, insula, and frontal cortex, in response to bladder filling. The aim of this study was to investigate the effect of SNS on brain activity in women with OAB.

Methods

We conducted a prospective mechanistic study of women with OAB (measured on validated questionnaire) undergoing InterStim®. Prior to stage 1 InterStim®, women underwent BOLD fMRI during bladder filling. During filling, women were asked to signal the experience of urgency. Women who completed stage 2 InterStim® underwent a 2nd BOLD fMRI during bladder filling 6 weeks after InterStim® implantation. Brain activity during urgency was compared to no urgency, and analysis was stratified according to response to InterStim®. _x000D_

Results

The study included 12 women with idiopathic OAB with normal emptying (median age 63.5, IQR 11 years). All women underwent pre-InterStim® fMRI, and 7 completed stage 2 InterStim® and underwent post-InterStim® fMRI (i.e. 7 responders, 5 non-responders). Among responders, brain activity decreased in the left cingulate gyrus (x,y,z coordinates: -5, 23, 39, p=0.048) and left frontal gyrus (-5, 23, 39, p=0.04) after InterStim® implantation (figure 1). There were no areas of increased brain activity after InterStim® implantation. Women who responded to InterStim® had increased brain activity on their pre-InterStim® fMRI in multiple cortical regions, including the cingulate cortex, inferior frontal gyrus, insula, and thalamus. There were no differences in ICIQ-FLUTS filling scores or pre-InterStim® fMRI filling volumes between responders and non-responders (p>0.05). _x000D_

Conclusions

SNS with InterStim® appears to attenuate increased brain activity in women with OAB. Women with OAB and increased brain activity during bladder filling may experience greater treatment response. fMRI has preliminarily detected a phenotype of OAB that may predict therapeutic response to InterStim®. _x000D_

Funding

SUFU Neuromoduation Grant Award