Ultrasound Could Enhance Stroke Survival by Clearing Brain Debris

Recent research suggests that pulsed ultrasound waves directed at the brain may enhance survival rates following a specific stroke type by promoting the removal of inflammatory dead blood cells, based on findings from a study involving mice. This technique, which boosts lymphatic drainage efficiency, could also have applications for treating Alzheimer’s disease, with clinical trials anticipated to commence next year.

Hemorrhagic stroke, constitutes around 15% of all strokes and occurs when a blood vessel in the brain bursts, leading to bleeding, disrupting oxygen supply to the brain, and causing cellular damage, which can result in motor and cognitive issues.

Treatments typically involve sealing the ruptured blood vessel with small metal clips and extracting dead red blood cells via a catheter or similar device. Neglecting this procedure can exacerbate inflammation and lead to further tissue damage. However, this method is highly invasive, posing risks of brain damage and infections, as noted by Larg Airan at Stanford University, California.

After an unexpected experience with prolonged ultrasound application during drug activation in mouse brains, Aylan considered whether pulsed ultrasound could be effective in removing the “debris” from the brain. “When I observed the drug’s effects, it appeared to spread throughout the brain, almost as if it were being ‘painted’ over,” he recounted.

To probe this idea, the research team simulated a hemorrhagic stroke by injecting mice with blood from their tails. For three consecutive days, they administered pulsed ultrasound to the skulls of half the mice for 10 minutes each day, while the others received no treatment.

Subsequently, all mice underwent a three-minute test in a water tank divided into four corners, with healthy mice typically turning in either direction 50% of the time. The team discovered that mice treated with ultrasound turned left 39% of the time, compared to 27% for the control group. Additionally, treated mice exhibited stronger grips on a metal bar than their untreated counterparts, indicating they suffered less brain damage, a conclusion that was later substantiated through brain slice analyses conducted post-euthanasia.

One week following the blood injection, around half of the control group mice perished, compared to only one-fifth of the ultrasound-treated group. A rapid increase in survival rates was noted, with an approximately 30 percentage point improvement achieved through just three 10-minute ultrasound treatments, according to Airan.

Further insights revealed that the ultrasound pulses triggered pressure-sensitive proteins in microglia, the brain’s immune cells, reducing their inflammation and enhancing their ability to clear dead red blood cells. Additionally, this technique improved the flow of cerebrospinal fluid, facilitating the removal of dead cells to lymph nodes in the neck, which are part of the lymphatic system responsible for eliminating metabolic waste.

While more investigations are necessary, this method might also have the potential to address various brain disorders. “If ultrasound can efficiently remove larger red blood cells from the brain, it stands to reason it could also eliminate smaller toxic proteins, such as the misfolded tau associated with Parkinson’s and Alzheimer’s diseases,” Aylan explained.

Experts are impressed with this promising research due to its non-invasive nature. Kathleen Caron from the University of North Carolina at Chapel Hill noted that the lymphatic systems in mice and humans show considerable similarities, indicating this approach could be applicable in human cases as well.

The use of ultrasonic irradiation is considered safe, and while research is ongoing to confirm these findings, Aylan is optimistic about the lack of unforeseen side effects from this treatment.

Ultimately, the research team aspires to test this technique on individuals suffering from hemorrhagic strokes that necessitate urgent intervention. They aim to gather additional data on its safety and efficacy for Alzheimer’s patients, with trials projected to begin next year, according to Aylan.