A new USC-led study using functional magnetic resonance imaging (fMRI) has revealed the neural mechanisms that contribute to urinary incontinence. Urinary incontinence is a common symptom affecting stroke survivors and has a significant impact on their quality of life.
This study was recently published strokewas conducted by a multidisciplinary team of urologists, neurosurgeons, and imaging experts from the Keck School of Medicine of Southern California, the Keck School of Medicine of Southern California, Rancho Los Amigos National Rehabilitation Center, and the Shirley Ryan Ability Lab. The research team found significant differences in brain activity during voluntary and involuntary bladder contractions, pointing to a possible pathway for targeted therapy.
Urinary incontinence affects up to 79% of patients immediately and persists after 1 year in almost 40% of survivors. This usually occurs due to uncontrolled bladder contractions and involuntary urine output, giving patients debilitating symptoms such as urinary urgency, frequency, and leakage. Although common, it is often undertreated. The condition also predicts worse long-term outcomes, including increased mortality and disability.
The brain plays a key role in bladder regulation, giving people the ability to sense when their bladder is full and delay urination until it is socially appropriate, or initiate urination on their own accord. In contrast, stroke survivors often struggle to suppress unwanted bladder contractions and may even lose bladder sensation and consciousness completely. Because stroke affects the brain, the normal pathways that control bladder control are disrupted. Nevertheless, the exact neurological basis of this dysfunction was poorly understood until recently. ”
Evgeny Kradin, MD, adjunct assistant professor of clinical urology and lead author of the study
This research played a key role in winning Kradin the McGuire-Zimskind Award from the Society of Urodynamics, Female Pelvic Medicine, and Genitourinary Reconstruction (SUFU). This award recognizes young professionals within 10 years of completing their training or fellowship who have made significant contributions to the field through basic and clinical research. The study utilized an innovative method in which participants repeatedly filled and urinated while inside the MRI, during which their brain function was measured.
“In contrast to previous studies in which participants using catheters entered the scanner with a full bladder and urinated as instructed, in our study we were able to repeatedly observe filling and urination. By simultaneously recording bladder pressure, we were able to distinguish between voluntary and involuntary micturition. “This allowed us to detect, for the first time, differences in brain activity during involuntary urination,” said Dr. Kei Zhang of the University of California, Mark and Mary Stevens Institute for Neuroimaging and Informatics. Keck School of Medicine. Jann develops analytical tools and clinical applications for functional MRI technology and served as the imaging expert for this study.
During voluntary bladder emptying, when participants consciously decided when to empty their bladder, both healthy people and stroke survivors showed significant activation in brain regions associated with sensorimotor control and executive decision making. In contrast, involuntary or incontinent bladder emptying in stroke survivors is characterized by minimal cortical activation, suggesting failure to engage key brain networks required for micturition control.
In both healthy people and stroke survivors, filling the bladder before voluntary urination triggered activity in a set of brain regions known as the salience network. These brain regions work together to assess the importance of internal or external stimuli and coordinate the brain’s response to those stimuli. However, in incontinent stroke survivors, this network remained inactive during bladder filling prior to involuntary micturition. These findings suggest that failure to engage the salience network may be a central mechanism underlying urinary incontinence after stroke.
These findings open the door to new interventions aimed at restoring bladder control in stroke patients. Possible treatment approaches include:
- Targeting the saliency network using non-invasive brain stimulation techniques such as transcranial magnetic stimulation (TMS) and direct current stimulation (tDCS)
- Development of drugs that enhance neural activation of important incontinence control regions
- Cognitive training and biofeedback therapy designed to improve bladder awareness and voluntary control
Although this study represents a major advance in understanding post-stroke incontinence, the researchers highlight the need for further investigation. Future research could investigate how different types of stroke affect urinary control and whether early intervention targeting the salience network could help prevent chronic incontinence in stroke survivors.
Dr. Charles Liu, director of the University of Southern California Center for Neural Recovery, senior author of this study, and coordinator of all collaborators, looks forward to further discoveries as this important research builds. “The neurological basis of urination is still not well understood, and further research will be important for neural recovery of the urinary and reproductive systems,” said Liu, professor of clinical neurosurgery, surgery, psychiatry and behavioral sciences, and biomedical engineering at the Keck School of Medicine. “This research not only improves our understanding of common post-stroke complications, but also offers hope for a better quality of life for millions of stroke survivors around the world.”
This study was funded by a grant from the Urological Care Foundation to Evgeny Kradin. Authors include Evgeny I. Kraydin, MD, Aydin Abedi, MD, Luis Morales, MD, Stefania Montero, MD, Priya Kohli, MD, BS, Ni Ha, MD, David Chapman, MD, Armita Abedi, MD, David Ginsburg, MD, Kay Yang, MD, Richard L. Harvey, MD, and Charles Y. Liu, MD. Ph.D.
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Keck School of Medicine, University of Southern California
