Motor Cortical Neuromodulation in Women With Interstitial Cystitis/Bladder Pain Syndrome

Overview

Interstitial Cystitis/Bladder Pain Syndrome (IC/BPS) is a common, chronic, and debilitating condition in women. Preliminary evidence suggests that IC/BPS pain can be reduced applying non-invasive repetitive transcranial magnetic stimulation (rTMS) to areas of the brain that regulate pelvic floor muscle activity. However, prior studies have examined rTMS in a very limited sample and have not examined changes in brain or pelvic floor muscle activity to determine the mechanism of rTMS for IC/BPS. This study is designed to directly address these limitations.

Interstitial Cystitis/Bladder Pain Syndrome (IC/BPS) is a common, chronic, and debilitating condition in women. The underlying cause of IC/BPS remains unknown. We recently published the first functional magnetic resonance imaging (fMRI) study comparing brain function in women with IC/BPS to healthy women. We found that women with IC/BPS have altered resting activity in supplementary motor area (SMA). Specifically, these changes appear in a part of SMA that we have shown to control pelvic floor muscle activity. We call this part of SMA "pelvic-SMA". Our results provide the first potential explanation for extensive published reports of increased pelvic floor muscle activity in women with IC/BPS. We hypothesize that we are observing evidence of an important theory of chronic pain: motor cortical changes occur that are initially beneficial to increase protective muscle activity but are ultimately maladaptive and perpetuate pain. If this theory is true, it should be possible to reduce pain and muscle activity by improving brain activity. The proposed work is to do exactly that. Using non-invasive repetitive transcranial magnetic stimulation (rTMS) directed at pelvic-SMA, we aim to determine if we can reduce pain (Aim 1), improve resting brain activity (fMRI) and resting pelvic floor muscle electromyographic (EMG) activity in IC/BPS (Aim 2), and to link the pain reductions to fMRI/EMG improvements to develop a causal mediation model of IC/BPS symptoms (Aim 3). We will recruit 50 women with IC/BPS to participate in the study, and participants will be randomized to 2 groups of 25: high-frequency (active) or sham (inert). Our preliminary data suggest that high-frequency stimulation is the best stimulation protocol for reducing pain and improving pelvic-SMA activity and resting pelvic floor muscle activity. Our preliminary results agree with a large body of literature suggesting that high-frequency rTMS applied to motor cortex is the best stimulus paradigm to reduce pain, but our proposed work has the potential to greatly innovate the field of non-invasive brain stimulation for pain by providing a mechanism by which the stimulation can improve deficiencies in motor function in chronic pain patients.