Functional magnetic resonance imaging during urodynamic testing identifies brain structures initiating micturition

Abstract

Purpose: Normal voiding in neurologically intact patients is triggered by the release of tonic inhibition from suprapontine centers, allowing the pontine micturition center to trigger the voiding reflex. Supraspinal mechanisms of voluntary voiding in humans are just beginning to be described via functional neuroimaging. We further elucidated brain activity processes during voiding using functional magnetic resonance imaging in normal females to gain better understanding of normal voiding as well as changes that may occur in voiding dysfunction.

Materials and methods: We screened 13 healthy premenopausal female volunteers using baseline clinic urodynamics to document normal voiding parameters. We then recorded brain activity via functional magnetic resonance imaging and simultaneous urodynamics, including the pressure flow voiding phase. After motion correction of functional magnetic resonance images we performed activation and connectivity analyses in 10 subjects.

Results: Group analysis revealed consistent activation areas, including regions for motor control (cerebellum, thalamus, caudate, lentiform nucleus, red nucleus, supplementary motor area and post-central gyrus), emotion (anterior/posterior cingulate gyrus and insula), executive function (left superior frontal gyrus) and a focal region in the pons. Connectivity analysis demonstrated strong interconnectivity of the pontine micturition center with many short-range and long-range cortical clusters.

Conclusions: Our study is one of the first reports of brain activation centers associated with micturition initiation in normal healthy females. Results show activation of a brain network consisting of regions for motor control, executive function and emotion processing. Further studies are planned to create and validate a model of brain activity during normal voiding in women.

Keywords: brain; central nervous system; magnetic resonance imaging; urinary tract; urination.

Conflict of interest statement

Financial interest and/or other relationship with Novartis, EM Kinetics, Astellas, Allergan and American Medical Systems.

Copyright © 2014 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.

Figures

Figure 1

A, average fMRI activation map shows activation in pons (micturition center), thalamus, cingulate gyrus, supplementary motor area and precentral gyrus. B, representative pressure time course from urology examination. Asterisks indicate start of voiding used in event related analysis of fMRI data (A).

Figure 2

A, clusters of highest fMRI activation derived from fMRI activation maps in see-through mode, allowing visualization of activation in entire brain. Note 18 clusters colored to serve as scale (cluster ordering). B, spring embedded network graphs of each subject show color coded clusters (A). Note small world behavior consisting of localized network node of high interaction in 1 cluster together with sparse long-range connectivity between clusters of most networks. C, 3D network display of subject 4 shows this small world behavior better than 2D graph networks.