The Future of Brain Imaging in Lower Urinary Tract Disorders

The Future of Brain Imaging in Lower Urinary Tract Disorders IF asked, “where in the cortex is the motor representation of the pelvic floor?” most of us would have probably conjured up the Penfield and Rasmussen homunculus and, based on assumptions about somatotopic continuity, suggested (because it has not actually been shown) that it is likely between the upper leg and trunk region on the motor strip. In this issue of The Journal Schrum et al (page 185) show that such an assumption would have been incorrect. In a simple experiment healthy volunteers were asked to voluntarily contract the pelvic floor at a fast or slow rate, paced by a metronome, in a magnetic resonance imaging scanner. As a comparison they moved their right toes quickly or slowly. The essential finding was that whereas toe movement was associated with (even caused by) activation of a discrete area of the motor strip, the expected result (according to the canonical homunculus) of pelvic floor contraction was not. Pelvic floor contraction at both speeds was convincingly associated with activity in the supplementary motor area as well as other regions which have come to be recognized as those associated with bladder sensory processing.1 Physiotherapists have long recognized that it is by contracting the pelvic floor that we can exert some control over bladder behavior. We are not neurologically equipped to exert direct voluntary control over the detrusor muscle but in many circumstances there is a need to suppress its activity. There are

experimental data to show hard wiring exists in the spinal cord such that sphincter and pelvic floor contraction has an inhibitory effect on detrusor contraction, and suppresses sensations of urgency,2 temporarily at least. What we are seeing in these results is presumably the neural operation of the initiation of a complex reflex process,3 quite unlike the relatively simple, primarily motor process of toe movement. This group of researchers has a track record of producing wonderful brain imaging of bladder related activation following simple maneuvers.4,5 Were it not for the complexity of subsequent analysis, studies like this could lead to a diagnostic role for functional brain imaging in various bladder disorders. However, that possibility is likely still a long way off. Nevertheless, it is appropriate that urologists should consider the findings of studies like this. Despite possibly being deterred by descriptions of brain imaging processes, the essential findings are simple and highly relevant to everyday functional urology practice. Clare J. Fowler* Department of Uro-Neurology National Hospital for Neurology and Neurosurgery London, United Kingdom

* Financial interest and/or other relationship with Allergan, Astratech and Astellas.

REFERENCES 1. Fowler CJ and Griffiths DJ: A decade of functional brain imaging applied to bladder control. Neurourol Urodyn 2010; 29: 49. 2. Fowler CJ, Griffiths D and de Groat WC: The neural control of micturition. Nat Rev Neurosci 2008; 9: 453.

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3. Griffiths D and Tadic SD: Bladder control, urgency, and urge incontinence: evidence from functional brain imaging. Neurourol Urodyn 2008; 27: 466. 4. Kuhtz-Buschbeck JP, van der Horst C, Pott C et al: Cortical representation of the urge to void: a func-

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tional magnetic resonance imaging study. J Urol 2005; 174: 1477. 5. Kuhtz-Buschbeck JP, Gilster R, van der Horst C et al: Control of bladder sensations: an fMRI study of brain activity and effective connectivity. Neuroimage 2009; 47: 18.

Vol. 186, 14, July 2011 Printed in U.S.A. DOI:10.1016/j.juro.2011.04.026