Since 2016, more than 150 U.S. personnel serving abroad in countries such as Russia, China, Cuba—and recently, Austria—have reported a sudden onset of severe headaches, dizziness and nausea. The mysterious illness is known as the “Havana Syndrome.”
While these symptoms typically are associated with a concussion, the usual causes of such an injury—a fall, blow to the head, or proximity to an explosion—weren’t at play.
There is speculation these people were victims of an attack from an invisible weapon known as directed microwave radiation, and the White House recently announced it would ramp up inquiries into who or what could have caused the incidents.
Christian Franck
A mechanical engineering professor at the University of Wisconsin-Madison, Christian Franck believes the idea of a directed microwave attack is spot-on, and he and his collaborators have shared new research on the preprint server bioRxiv that supports that notion.
An expert in understanding the mechanics and biology of how cells respond to a traumatic brain injury, Frank is director of PANTHER, a transdisciplinary research initiative funded with $10 million from the U.S. Office of Naval Research that brings together scientists from academia, industry and government to study traumatic brain injury through a range of approaches.
In the new research, Franck leveraged a technique called inertial microcavitation that allowed him to mimic the effects of an explosion, or directed energy exposure, on different regions within neural cells.
Cavitation occurs when a liquid’s static pressure drops below its vapor pressure, leading to small vapor-filled bubbles. Exposed to higher pressure, the bubbles then collapse and generate shock waves and forces strong enough to damage adjacent materials—in this case, brain tissue.
Using a 3D in vitro neural tissue model, Franck and his collaborators found that, under “blast-like” conditions, neural cells’ microtubules and filamentous actin could withstand higher physical strain than neuronal dendritic spines. Those results aligned with injury thresholds previously reported for lower and moderate strain rates.
What stood out, however, is that those blast-like conditions produced only physical injuries to the brain cells—rather than also biochemically activated cell degeneration, as is typical during an injury caused by a fall or blow to the head. “This is a new kind of insult to the brain that we haven’t seen,” says Franck. “From a clinical perspective, it’s a different type of injury.”
Franck says that when he first read research describing the brain injuries U.S. personnel sustained in Cuba, he was perplexed. “There were lots of places where we noticed significant changes in the volume of white matter (which is found in deeper tissues of the brain), but it didn’t seem consistent with the pathology we know from concussions,” he says. “The authors suggested in the paper that it might be a new pathology. There were significant cognitive defects in the individuals, and their recovery time was much longer than it might be for just a concussion.”
What was missing from that research, however, was understanding of how the injuries occurred in the first place. “It looked like blast pathology, but how did it happen?” asks Franck.
Digging deeper, he found a research team that had simulated neural cells’ exposure to microwaves, resulting in enough of a temperature increase to cause thermal stress in the cells.
And for Franck, that’s how everything clicked into place. The physics, he says, point to microwaves as a very plausible explanation—in the absence of an explosion—for how those mysterious brain injuries occurred. “When a microwave is pulsed, waves bounce around and generate larger stresses and pressures,” he says. “Those pressures can give rise to cavitation, which generates very large and fast stresses on brain tissue. That’s the origin of the pathology we’re seeing.”
Frank and his collaborators now are working to experimentally verify the hypothesis that microwaves can generate the kinds of pressures needed to produce cavitation that causes trauma to brain cells. He hopes to be able to consult with governmental agencies and others on developing technologies to detect a microwave attack and countermeasures to keep people out of harm’s way.
Involving researchers across the country who combine depth and breadth of expertise around traumatic brain injury, PANTHER uniquely positions UW-Madison to be a leader in those solutions, says Franck. “If there is going to be a response to try to safeguard people, Wisconsin is one of the universities that could certainly help,” he says.