How does the brain get rid of waste? It relies on a specialized drainage network known as the lymphatic system. Scientists have been working to understand how this system functions, and in the process, they have pushed brain imaging technology to new limits.
A new study published in iScience by researchers at the Medical University of South Carolina (MUSC) provides the first direct evidence in humans of a previously unknown control point in this system. The structure is the middle meningeal artery (MMA), which now appears to play a key role in how the brain clears out fluids and waste.
Real-Time MRI Reveals Brain Fluid Flow
The research team, led by Onder Albayram, Ph.D., used advanced real-time MRI tools made available through a NASA collaboration. These imaging techniques were originally designed to study how spaceflight changes fluid movement in the brain.
Using this technology, the team monitored the movement of cerebrospinal and interstitial fluids along the MMA in five healthy individuals over six hours. What they observed was unexpected. The fluid moved slowly and steadily, unlike blood, which flows quickly and dynamically. This slower pattern suggested that the fluid was part of the lymphatic system rather than the circulatory system.
“We saw a flow pattern that didn’t behave like blood moving through an artery; it was slower, more like drainage, showing that this vessel is part of the brain’s cleanup system,” said Albayram, an associate professor in the Department of Pathology and Laboratory Medicine at MUSC.
Rethinking the Brain’s Connection to the Body
The brain and spinal cord are protected by layered membranes called the meninges. For many years, scientists believed these membranes separated the brain from the body’s immune and lymphatic systems. That view has changed significantly over the past decade.
Albayram has spent years studying lymphatic vessels within the meninges. His work suggests these vessels act as channels that carry waste away from the brain and into the body’s broader lymphatic network, where it can be removed.
Understanding how fluids move between the brain and the rest of the body is critical. It may help researchers develop better ways to prevent and treat neurological and psychiatric conditions.
Imaging Confirms a True Lymphatic Pathway
Albayram previously helped visualize these meningeal lymphatic vessels in humans, as reported in a 2022 Nature Communications study. In this new work, the team captured real-time fluid movement deep within the brain’s lymphatic structures.
To verify their findings, the researchers also examined human brain tissue using ultra high-resolution imaging. In collaboration with scientists at Cornell University, they used a method that allows multiple cell types to be seen simultaneously.
This detailed analysis showed that the region surrounding the MMA contains cells typically found in lymphatic vessels. These are the same types of structures responsible for clearing waste throughout the body.
Together, the imaging and tissue data confirmed that the slow-moving fluid observed on MRI was traveling through lymphatic vessels, not blood vessels, directly linking the scans to biological evidence.
Why Studying Healthy Brains Matters
A key feature of this research is its focus on studying healthy people first, rather than starting with animal models. This approach allows scientists to establish a clear baseline of how the system works under normal conditions.
That baseline is essential for identifying what changes in disease. For example, disruptions in this drainage system may play a role after traumatic brain injury or in neurodegenerative diseases.
Implications for Alzheimer’s and Brain Disorders
The discovery could have wide-reaching implications. It may help scientists better understand aging, inflammation in the brain, injury, Alzheimer’s disease and psychiatric conditions.
Albayram is already building on these findings by studying how this drainage system behaves in people with neurodegenerative diseases. The long-term goal is to improve early diagnosis, develop preventive strategies and create more effective treatments.
“A major challenge in brain research is that we still don’t fully understand how a healthy brain functions and ages,” said Albayram. “Once we understand what ‘normal’ looks like, we can recognize early signs of disease and design better treatments.”
