Baseline Brain Segmental Volumes in Responders and Nonresponders to Anticholinergic Therapy for Overactive Bladder Syndrome

Abstract

Objective Evaluate structural differences in brains of responders (R) and nonresponders (NR) to anticholinergic (AC) therapy for overactive bladder (OAB). Materials and Methods This was a retrospective cohort study of age matched women treated with an AC medication for OAB and underwent magnetic resonance imaging within 12 months before treatment. Data on pretreatment demographic and clinical variables and symptom severity was also collected. T1-weighted magnetic resonance images of the brain for each subject were segmented using FreeSurfer software. Structures included for analysis were cerebral cortex, white matter, subcortical gray matter, cerebellum, and brain stem. Nonresponders were defined as patients who reported less than 50% improvement after a minimum of 4 weeks on the maximum dose of the prescribed medication. Pairwise analysis between groups was performed using the Wilcoxon-Rank Sum test and Fisher exact test where appropriate. Spearman ρ was used to evaluate for correlations between neurologic structures and symptom severity. Results There were no differences in pretreatment characteristics or symptom severity between the 21 R and 18 NR. Nonresponders had lower volumes of the right caudal anterior cingulate gyrus white matter (1919 mm3 vs 2416 mm3, P = 0.008) and right parahippocampal gyrus white matter (1008 mm3 vs 1469 mm3, P = 0.001). Incontinence episode frequency showed a negative moderate correlation with the anterior cingulate gyrus white matter volume (ρ = −0.4228, P = 0.007). The right and left cerebellar cortices showed weak and moderate negative correlations to frequency of nocturia (ρ = −0.384, P = 0.02 and ρ −0.443, P = 0.005, respectively). Conclusion There are measurable volumetric differences in brain structures in R and NR to AC therapy.