A new USC-led study using functional magnetic resonance imaging (fMRI) reveals the neural mechanisms that contribute to urinary incontinence, a common condition affecting stroke survivors that has a significant impact on their quality of life.
The research, just published in Rapwas conducted by a multidisciplinary team of urologists, neurosurgeons and imaging experts from the Keck School of Medicine of USC, Keck Medicine of USC, Rancho Los Amigos National Rehabilitation Center and the Shirley Ryan Ability Lab. The team discovered significant differences in brain activity during voluntary versus involuntary bladder contractions, presenting potential avenues for targeted therapies.
Urinary incontinence affects up to 79% of patients soon after and persists in nearly 40% of survivors one year later. It typically results from uncontrolled bladder contractions and involuntary voiding of urine, leaving patients with debilitating symptoms such as urinary urgency, frequency, and leakage. Although common, it is often undertreated. This condition also predicts worse long-term outcomes, including higher mortality rates and increased disability.
The brain plays a key role in bladder regulation, allowing people to feel bladder fullness and enabling them to delay urination until it is socially appropriate or initiate it at will. Conversely, stroke survivors often struggle to suppress unwanted bladder contractions and may even lose bladder sensation and awareness altogether. Since a stroke affects the brain, it disrupts the normal pathways that govern bladder control. However, the precise neurological underpinnings of this dysfunction remained poorly understood until recently.”
Evgeniy Kreydin, MD, assistant professor of clinical urology and lead author of the study
This research was instrumental in Kreydin receiving the McGuire-Zimskind Award from the Society for Urodynamics, Pelvic Medicine and Genitourinary Reconstruction (SUFU). The award honors early career professionals within ten years of completing residency or fellowship who have made significant contributions to the field through basic and clinical research. The study used an innovative method of repeatedly filling and voiding the bladder while the participants were inside an MRI, during which their brain function was measured.
“Unlike previous studies where participants using a catheter entered the scanner with a full bladder and voided on command, our study allowed us to repeatedly observe filling and voiding. Simultaneous recording of bladder pressure allowed us to identify both voluntary and involuntary bladder emptying. USC Mark and Mary Stevens Neuroimaging and Informatics Institute at the Keck School of Medicine. Jann develops analytical tools and clinical translations of functional MRI technology and served as an imaging expert for the study.
During voluntary bladder emptying, when participants consciously decided when to empty their bladder, both healthy subjects and stroke survivors showed significant activation in brain regions associated with sensorimotor control and executive decision making. In contrast, involuntary or incontinent voiding in stroke survivors was characterized by minimal cortical activation, suggesting a failure to engage key brain networks necessary for urinary control.
In both healthy subjects and stroke survivors, filling the bladder before voluntary urination triggered activity in a collection of brain regions known as the salience network. These brain regions work together to assess the significance of internal or external stimuli and coordinate the brain’s response to those stimuli. However, during bladder filling that preceded voiding, this network remained inactive for incontinent stroke survivors. These findings suggest that failure to engage the salient network may be a key 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 could include:
- Using non-invasive brain stimulation techniques, such as transcranial magnetic stimulation (TMS) or direct current stimulation (tDCS), to target the salient network
- Development of drugs that enhance neural activation in critical areas of continence control
- Cognitive training and biofeedback therapies designed to improve bladder awareness and voluntary control
While the study represents a major advance in understanding post-stroke incontinence, the researchers stress the need for further research. Future studies could investigate how different types of stroke affect urinary control and whether early intervention targeting the salient network could help prevent chronic incontinence in stroke survivors.
Charles Liu, PhD, MD, director of the USC Neurorestoration Center, senior author of the study and coordinator of all collaborators, is optimistic for further discovery as this important research builds. “The neurological basis of micturition is still poorly understood, and additional research will be crucial for neurorehabilitation of the urinary and reproductive systems,” said Liu, who is also a professor of clinical neurosurgery, surgery, psychiatry, and behavioral sciences and biomedical engineering at the Keck School of Medicine. “This work not only deepens our understanding of a common complication after stroke, but also provides hope for a better quality of life for millions of stroke survivors worldwide.”
This study was funded by a grant from the Urology Care Foundation to Evgeniy Kreydin. Authors include Evgeniy I. Kreydin, MD, Aidin Abedi, MD, Luis Morales, MD, Stefania Montero, MD, Priya Kohli, BS, Nhi Ha, BS, David Chapman, MD, Armita Abedi, MD, David Ginsberg, MD, Kay Jann, PhD, Charvey YMD, LMD. PhD.
