Structural Changes in Brain White Matter Tracts Associated With Overactive Bladder Revealed by Diffusion Tensor Magnetic Resonance Imaging: Findings From a Symptoms of Lower Urinary Tract Dysfunction Research Network Cross-Sectional Case-Control Study

Abstract

Purpose: Our objective was to investigate structural changes in brain white matter tracts using diffusion tensor imaging (DTI) in patients with overactive bladder (OAB).

Materials and methods: Treatment-seeking OAB patients and matched controls enrolled in the cross-sectional case-control LURN (Symptoms of Lower Urinary Tract Dysfunction Research Network) Neuroimaging Study received a brain DTI scan. Microstructural integrity of brain white matter was assessed using fractional anisotropy (FA) and mean diffusivity. OAB and urgency urinary incontinence (UUI) symptoms were assessed using the OAB Questionnaire Short-Form and International Consultation on Incontinence Questionnaire-Urinary Incontinence. The Lower Urinary Tract Symptoms Tool UUI questions and responses were correlated with FA values.

Results: Among 221 participants with evaluable DTI data, 146 had OAB (66 urinary urgency-only without UUI, 80 with UUI); 75 were controls. Compared with controls, participants with OAB showed decreased FA and increased mean diffusivity, representing greater microstructural abnormalities of brain white matter tracts among OAB participants. These abnormalities occurred in the corpus callosum, bilateral anterior thalamic radiation and superior longitudinal fasciculus tracts, and bilateral insula and parahippocampal region. Among participants with OAB, higher OAB Questionnaire Short-Form scores were associated with decreased FA in the left inferior fronto-occipital fasciculus, P < .0001. DTI differences between OAB and controls were driven by the urinary urgency-only (OAB-dry) but not the UUI (OAB-wet) subgroup.

Conclusions: Abnormalities in microstructural integrity in specific brain white matter tracts were more frequent in OAB patients. More severe OAB symptoms were correlated with greater degree of microstructural abnormalities in brain white matter tracts in patients with OAB.

Trial registration: ClinicalTrials.gov: NCT02485808.

Keywords: brain MRI; diffusion tensor imaging; overactive bladder; urgency urinary incontinence.

Figure 1A.

DTI FA results, OAB versus controls. Green color indicates p>0.05. Red/orange color indicates p<0.05, with the FA values in OAB statistically lower than those in controls in these tracts.

Figure 1B.

DTI MD results, OAB versus controls. Green color indicates p>0.05. Blue color indicates p<0.05, with MDs values in OAB statistically higher than those in controls in these tracts. (Blue color is used for statistical difference in Figure 1B since the values of OAB > controls, while red/orange color is used for statistical difference in Figure 1A since the values of OAB < controls. Green color indicates no differences in both figures.)

Figure 2A.

Correlation between FA and OAB-q symptoms among OAB participants. Green color indicates p>0.05. Blue color indicates p<0.05, with negative correlations between FA and OAB-q in the brain white matter tracts shown.

Figure 2B.

Negative correlation between FA and OAB-q among OAB participants.

Figure 3A.

DTI FA results, UU versus controls. Green color indicates p>0.05. Red/orange color indicates p<0.05, with MD values in UU statistically higher than those in controls in these tracts.

Figure 3B.

DTI MD results, UU versus controls. Green color indicates p>0.05. Blue color indicates p<0.05, with MDs values in UU statistically higher than those in controls in these tracts.