Advancements in neuroimaging modalities have enabled the evaluation of neural control over the lower urinary tract (LUT). Despite this significant progress, there remains a limited understanding of how stroke location influences LUT dysfunction in stroke survivors. In order to gain a more comprehensive understanding of this relationship, this original study is the first to measure and compare micturition-associated brain activity patterns in patients who suffered from strokes in the basal ganglia versus those with pontine strokes.

This prospective study was approved by our Institutional Review Board, and all participants provided informed consent prior to enrollment. Patients with a history of post-stroke LUT dysfunction resulting from chronic (>1 year) basal ganglia or pontine strokes of either embolic or hemorrhagic etiologies were enrolled. The severity of LUT symptoms was assessed and compared using the International Consultation on Incontinence Overactive Bladder (ICIQ-OAB) questionnaire. Micturition-related brain activity was assessed using simultaneous urodynamics and blood-oxygen-level-dependent (BOLD) functional magnetic resonance imaging (fMRI). Statistical parametric mapping was used to compare BOLD signals during the period of maximal urgency (10 seconds before a detrusor contraction) between basal ganglia and pontine strokes, and brain regions with differential activation were identified using a conservative p value threshold of <0.01 and cluster size of >25 voxels. In order to identify typical activations, simulations have indicated that a sample size of at least 12 subjects would achieve 80% power at the single-voxel level. To account for the potential confounding factors, our models were adjusted for age, gender, and time since stroke.

A total of 19 patients, including ten patients with basal ganglia strokes and nine patients with pontine lesions were enrolled. There was no significant difference in the ICIQ-OAB scores between the basal ganglia and pontine strokes (8.6±3.7 versus 8.1±4.4, p=0.56). There were no clusters of increased BOLD activity in patients with basal ganglia strokes. On the other hand, 22 clusters were identified that showed increased BOLD activity in patients with pontine strokes. Compared to basal ganglia strokes, patients with pontine strokes exhibited increased BOLD signal in the right midbrain, bilateral cerebellum, right insula, right middle and superior temporal gyri, right supramarginal gyrus, right precuneus, right postcentral gyrus, right inferior and middle frontal gyrus, as well as left basal ganglia.

Our study provides evidence that stroke location plays a critical role in the mechanism of stroke-related LUT dysfunction. In this cohort of patients with similar LUT symptoms, we observed marked differences in BOLD signal between basal ganglia and pontine strokes. These differences were identified across several brain regions that are critical for somatosensory, interoceptive and executive function, all of which have previously been shown to play a role in LUT control. Based on these findings, we propose the hypothesis that the basal ganglia may act as a gateway for LUT processing between the cortex and the rest of the central nervous system.

To our knowledge, the present study is the first of its kind to provide significant insights into the neural mechanisms underlying LUT dysfunction in relation to stroke location. Previous studies have attempted to correlate LUT symptoms with stroke location, but none have been successful in defining a clear relationship. By identifying the key differences in brain activity across stroke locations, this study sheds a broader light on the complex relationship between LUT symptoms, stroke location, and central nervous system mechanisms of LUT control.

Continence 7S1 (2023) 100761
DOI: 10.1016/j.cont.2023.100761