The brain has its own built-in cleaning system. Instead of soap and water, it uses cerebrospinal fluid—a clear liquid that flows around the brain and washes away waste, toxins, and stray blood cells.
But this natural cleansing system becomes less efficient as we age or after brain injuries such as strokes.
Until now, there have been no easy or safe ways to help the brain clean itself better.
A team of Stanford University researchers may have found a surprisingly simple solution: ultrasound.
The same safe, noninvasive technology used in prenatal checkups could help flush waste from the brain and reduce inflammation.
Their new study, published in Nature Biotechnology, shows that ultrasound treatments helped mice clear out harmful debris and improved their brain health.
Raag Airan, a radiology professor at Stanford Medicine and senior author of the study, says the technique could soon be tested in humans.
With support from Stanford’s Knight Initiative for Brain Resilience, his team is developing a wearable ultrasound “helmet” designed to deliver gentle ultrasound waves to the human brain.
The origins of this discovery go back to an accident. Years ago, while experimenting with ultrasound at Johns Hopkins University, Airan accidentally left an ultrasound device running continuously when it should have been pulsed briefly.
When he reviewed the data, he was surprised to see that the drug he was tracking in the brain had smeared far beyond the expected area. It looked as if something had stirred the fluid deep inside the brain.
That mistake raised an intriguing possibility: could ultrasound help move cerebrospinal fluid and enhance the brain’s cleaning process?
To test this idea, Airan and graduate student Matine Azadian created a mouse model of hemorrhagic stroke by injecting blood into the brain.
This type of stroke leaves behind floating blood cells that block fluid flow and trigger inflammation. The team wanted to see whether ultrasound could remove these blood cells more effectively.
Half of the mice received three short ultrasound treatments. The others received fake treatments with the machine turned off. The results were striking. Mice that received ultrasound had less than half the leftover blood in their cerebrospinal fluid compared with untreated mice.
They also showed fewer signs of brain inflammation and performed better on mobility tests. Most importantly, survival rates rose sharply—from 50 percent in untreated mice to 83 percent in mice treated with ultrasound.
The team then explored how the process works. At first, they thought ultrasound directly stirred the cerebrospinal fluid, but they noticed that fluid movement continued long after the ultrasound was turned off.
This suggested a more complex biological response. Azadian proposed that vibration-sensitive channels in brain cells were being activated, triggering a longer-lasting fluid-moving mechanism inside the brain.
More research is underway, but the early findings are promising. If this simple, noninvasive method works in humans, it could provide a powerful new way to support aging brains, treat stroke damage, and improve overall brain health—using nothing more than gentle sound waves.
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