Spinal cord’s role in bladder control uncovered
Scientists have identified how the spinal cord regulates bladder emptying in humans, a discovery that could lead to new treatments for urinary incontinence.
Using functional ultrasound imaging (fUSI), researchers visualised spinal cord activity in real time during bladder filling and emptying – the first time this has been directly observed in humans.
Urinary incontinence, which affects more than 33 million people in the US, is a common feature of neurological disorders and can severely affect mental health and quality of life.
The study involved patients undergoing routine epidural spinal cord stimulation surgery for chronic low back pain, offering a safe and unique opportunity to access the spinal cord during an existing surgical opening.
fUSI is a minimally invasive imaging technique that measures changes in blood volume. It was used to observe activity in specific spinal cord regions during a simulated bladder cycle, without adding risk to patients.
Vasileios Christopoulos, assistant professor in biomedical engineering at USC Viterbi School of Engineering, said: “This is the first study where we’ve shown that there are areas in the spinal cord where activity is correlated with the pressure inside the bladder.
“Nobody had ever shown a network in the spinal cord correlated with bladder pressure.
“What this means is I can look at the activity of your spinal cord in these specific areas and tell you your stage of the bladder cycle – how full your bladder is and whether you’re about to urinate.”
The spinal cord regulates essential autonomic functions including bladder, bowel and sexual control.
These can be lost due to spinal injury, stroke, ageing or disease. However, studying the spinal cord has been limited by its small size and bony structure.
Unlike the brain, spinal cord function is rarely assessed using invasive electrodes, due to the risk of paralysis.
Standard MRI is also impractical in the thoracic and lumbar spine, where many critical autonomic functions are located.
Christopoulos said: “The spinal cord is a very undiscovered area.
“It’s very surprising to me because when I started doing neuroscience, everybody was talking about the brain.
“And Dr Liu and I asked, ‘What about the spinal cord?’
“For many, it was just a cable that transfers information from the brain to the peripheral system.
“The truth was that we didn’t know how to go there – how to study the spinal cord in action, visualise its dynamics and truly grasp its role in physiological functions.”
During the procedures, while surgical teams implanted spinal stimulators, the research team filled and emptied patients’ bladders with saline under anaesthesia to simulate a full bladder cycle and record fUSI data.
They found that some spinal cord regions increased activity as bladder pressure rose (positive correlation), while others showed decreased activity (negative correlation), suggesting the presence of both excitatory and inhibitory control networks.
Kofi Agyeman, biomedical engineering postdoctoral scholar and co-first author, said: “It was extremely exciting to take data straight from the fUSI scanner in the OR to the lab, where advanced data science techniques quickly revealed results that have never been seen before, even in animal models, let alone in humans,” said
Christopoulos noted that for people living with spinal cord injury, regaining control of bladder, bowel and sexual function is often more important than restoring mobility.
The researcher said: “If you ask these patients, the most important function they wanted to restore was not their motor or sensory function.
“It was things like sexual function and bowel and bladder control. It’s a very dehumanising problem to deal with.”
