ARI SHAPIRO, HOST:
An update on the U.S. government workers who had health problems while in Cuba. The State Department says they sustained brain injuries from some sort of attack. Several prominent brain scientists have challenged that conclusion. And now, as NPR's Jon Hamilton reports, a new study appears to back those scientists.
JON HAMILTON, BYLINE: In 2016, dozens of people associated with the embassy in Havana began hearing a high-pitched noise or feeling a wave of pressure. Then they experienced dizziness, headaches, sleep problems and foggy thinking. The workers were sent to the University of Pennsylvania's Center for Brain Injury and Repair. They got MRI scans. And Ragini Verma, a professor of radiology, says the scans looked normal.
RAGINI VERMA: Just a traditional read of the images did not reveal much.
HAMILTON: So Verma and a team decided to use advanced imaging techniques usually reserved for scientific research. The team studied 40 government workers who'd reported symptoms of what's become known as Havana syndrome. Then they compared these images with images from groups of healthy people. Verma says this time, the team did find something.
VERMA: The most important thing is that there were group differences.
HAMILTON: Subtle differences in brain volume, brain networks and in the structure of brain tissue. The structural differences were most apparent in the cerebellum, an area involved in balance and movement. But Verma says there was no evidence of traumatic brain injury.
VERMA: All the imaging differences that we see do not reflect the imaging differences that we see in TBI or concussion.
HAMILTON: And Verma says it's hard to know what the differences mean.
VERMA: All you can say is something happened, which caused their brain to change. And those are reflected in their clinical symptoms and their imaging results.
HAMILTON: Of course, what everybody has been asking about is is there evidence that these people were attacked or not? Does this study answer that question?
HAMILTON: The study appears in JAMA along with an editor's note saying its clinical relevance is uncertain. Doug Fields, a neuroscientist who has investigated the events in Cuba, says that's an understatement.
R DOUGLAS FIELDS: First of all, these techniques are not diagnostic. They're descriptive, and they don't provide any clinical evidence of any kind of abnormality or pathology. What they show are minor differences between two groups.
HAMILTON: And Fields says group differences are pretty common.
FIELDS: These methods are used to find differences that are associated with being left-handed or right-handed or male or female, high IQ, low IQ, whether you're a musician or not. But they're all within normal range.
HAMILTON: Fields says the significance of the study is in what it did not find.
FIELDS: If there'd been brain injury, that would have been evident on the clinical brain imaging studies that were done before. And there was no evidence of any pathology. And these more sophisticated measures confirm that.
HAMILTON: Fields says the new results should end speculation that embassy workers were injured by a sonic weapon or something even more exotic.
FIELDS: The physical evidence to support the idea that there was some sort of a energy beam is completely lacking.
HAMILTON: The State Department did not respond to requests for comment.
Jon Hamilton, NPR News.
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