Brain Activity Linked to Urinary Incontinence in Stroke Survivors

A recent study led by the University of Southern California (USC) has uncovered critical brain activity patterns involved in urinary incontinence, a condition that affects a significant number of stroke survivors. The research, published in Stroke, offers new insights into the neural mechanisms that contribute to this common and often debilitating condition, opening the door for potential therapies aimed at improving bladder control in stroke patients.

The impact of urinary incontinence in stroke survivors

Urinary incontinence is a prevalent issue among stroke survivors, affecting up to 79% of patients in the immediate aftermath of the event, with nearly 40% continuing to experience it one year later. The condition typically results from uncontrolled bladder contractions, causing involuntary urine expulsion. This leads to symptoms such as urinary urgency, frequency and leakage, which severely impact the quality of life. Untreated incontinence is linked to poorer long-term outcomes, including increased mortality rates and disability.

Despite its widespread nature, urinary incontinence in stroke survivors remains undertreated. The exact neurological basis for this dysfunction has been unclear, particularly how the brain’s pathways governing bladder control are disrupted following a stroke. The USC-led study sheds light on these mechanisms, offering new potential pathways for targeted interventions.

Key findings from functional magnetic resonance imaging (fMRI)

The research team used functional magnetic resonance imaging (fMRI) to investigate brain activity during both voluntary and involuntary bladder contractions in stroke survivors. This approach provided a more comprehensive view of the brain's involvement in bladder control compared to previous studies.

“The brain plays a crucial role in regulating the bladder, allowing people to sense bladder fullness and giving them the ability to delay urination until it is socially appropriate or initiate it at will. In contrast, stroke survivors often struggle to suppress unwanted bladder contractions and may even lose bladder sensation and awareness entirely. Since a stroke impacts the brain, it disrupts the normal pathways that govern bladder control. Nevertheless, the precise neurological foundations of this dysfunction have remained poorly understood until recently.”

Dr. Evgeniy Kreydin.

A key component of this research was the method of repeated bladder filling and voiding while participants underwent fMRI scanning. Unlike earlier studies, which only allowed participants to void on command, the new method enabled the team to observe bladder filling and emptying cycles repeatedly. This setup also allowed the researchers to measure bladder pressure in real-time, distinguishing between voluntary and involuntary bladder emptying.

Differences in brain activity

The study revealed differences in brain activity between voluntary and involuntary bladder emptying. During voluntary urination, when participants consciously decided when to empty their bladder, both healthy individuals and stroke survivors showed activation in brain regions linked to sensorimotor control and decision-making. In contrast, stroke survivors who experienced involuntary bladder emptying displayed minimal activation in these regions, indicating a failure to engage the brain networks necessary for urinary control.

Bladder filling before voluntary urination also activated a collection of brain regions known as the salience network, which is involved in evaluating stimuli and coordinating responses. However, when bladder filling preceded involuntary urination in stroke survivors, this network remained inactive. The failure to activate the salience network may be a core mechanism underlying urinary incontinence in stroke patients.

Implications for therapy

These findings open up new possibilities for therapeutic interventions aimed at restoring bladder control in stroke survivors. The researchers suggest several potential approaches, including:

• Non-invasive brain stimulation techniques, such as transcranial magnetic stimulation (TMS) or direct current stimulation (tDCS), to target the salience network and improve bladder control.

• Medications that could enhance neural activation in critical regions responsible for urinary continence.

• Cognitive training and biofeedback therapies to improve bladder awareness and voluntary control.

While these interventions are promising, the researchers emphasize the need for further investigation. Future studies could explore how different types of strokes affect urinary control and whether early intervention targeting the salience network can prevent chronic incontinence in stroke survivors.

Next steps in research

Senior author Dr. Charles Liu, director of the USC Neurorestoration Center and a professor at the Keck School of Medicine, expressed optimism about the future of this research. He highlighted the importance of further studies to deepen the understanding of the neurological foundations of urination, especially in the context of stroke recovery.

“This work not only advances our understanding of a common post-stroke complication but also holds the potential to improve the quality of life for millions of stroke survivors globally,” said Liu.

Reference: Kreydin EI, Abedi A, Morales L, et al. Neural mechanisms of poststroke urinary incontinence: results from an fMRI study. Stroke. 0(0). doi: 10.1161/STROKEAHA.124.048057

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