Functional Magnetic Resonance Imaging of the Brain in Women With Overactive Bladder

In Brief Objectives: To identify abnormal function of the limbic cortex (LC) in response to urinary urgency among patients with overactive bladder (OAB) using brain functional magnetic resonance imaging. Methods: For this study, 5 OAB subjects and 5 controls underwent bladder filling and rated urgency sensations while functional magnetic resonance imaging measured activation in discrete volumes (voxels) within the brain. Changes in brain activation were related to bladder distension and individual subject's rating of urgency via multiple regression analysis. β Weights from regression equations were converted into percent signal change for each voxel and percent signal change compared with the null hypothesis using t tests. Significance threshold of P < 0.05 was applied along with a cluster size threshold of 0.32 mL (5005 voxels left ACG). Results: Patients with OAB showed increased brain activation in LC, specifically the insula (IN) and anterior cingulate gyrus, associated with increased urgency. Urgency sensations during low volumes were associated with bilateral IN activation in OAB subjects (7621 voxels right IN and 4453 voxels left IN, mean β weights = 0.018 ± 0.014 and 0.014 ± 0.011). Minimal activation was present in controls (790 voxels right IN, β weight = 0.010 ± 0.007). Urgency sensations during high volumes were associated with bilateral anterior cingulate gyrus activation in OAB subjects (2304 voxels right ACG and 5005 voxels left IN, mean β weights = 0.005 ± 0.003 and 0.004 ± 0.003) without activation in controls. Conclusions: Urinary urgency in patients with OAB is associated with increased activation of the LC. This activation likely represents abnormal processing of sensory input in brain regions associated with emotional response to discomfort. We sought to identify the brain's response to urinary urgency among women with Overactive bladder (OAB) using brain functional MRI (fMRI). We found that urinary urgency in OAB subjects was associated with increased activation of the limbic cortex.