A close look at the brains of 40 U.S. Embassy workers in Cuba who developed mysterious symptoms has found no evidence of injury. The State Department has said the employees were hurt by some sort of attack.
Advanced brain imaging techniques did reveal some subtle differences in the workers' brains, says Ragini Verma, a professor of radiology at the University of Pennsylvania and an author of the study published in this week's JAMA, the journal of the American Medical Association.
But those differences "do not reflect the imaging differences that we see in [traumatic brain injury] or concussion," Verma says.
"All you can say is something happened, which caused their brain to change," she says.
And even that conclusion was challenged by brain scientists who have been skeptical that any diplomat was attacked or injured from what became known as "Havana syndrome."
The differences could have been random or simply the result of different life experiences that can change the brain — like learning a foreign language, says Sergio Della Sala, a professor of human cognitive neuroscience at the University of Edinburgh in the U.K. He called the study in JAMA "half-baked."
"There is no evidence of any pathology," says Douglas Fields, a neuroscientist who has investigated and written about the events in Cuba. "And when you look at the data, there's no coherent syndrome, no pattern."
The new results should end speculation that embassy workers were injured by a sonic weapon or something even more exotic, Fields says.
"The physical evidence to support the idea that there was some sort of an energy beam is completely lacking," he says.
The study is the latest development in a mystery that began in 2016, when dozens of people associated with the U.S. Embassy in Havana began reporting strange, high-pitched sounds or sudden changes in air pressure. Shortly after these events, they began experiencing dizziness, headaches, sleep problems, hearing problems and foggy thinking.
The State Department began referring those workers to the University of Pennsylvania's Center for Brain Injury and Repair.
In 2018, doctors there reported in JAMA that 21 workers had symptoms that resembled those of a traumatic brain injury or concussion.
As part of their evaluation, people sent to the University of Pennsylvania also got MRI brain scans, which appeared normal.
"Just a traditional read of the images did not reveal much," Verma says.
Verma and several colleagues decided to take another look using advanced imaging techniques usually reserved for scientific research.
They studied brain scans from 40 government workers who had reported symptoms. Then they compared those images with brain images from groups of healthy people.
This time, the team did find something.
"The most important thing is that there were differences," Verma says.
The differences were subtle and involved measures of brain volume, brain networks and the fibers that carry signals around the brain. They were most apparent in an area called the cerebellum, which is involved in balance and movement, and were also found in areas of the brain that process sound.
Differences in those areas, Verma says, might help explain why the workers reported symptoms involving balance and hearing.
But Fields says even that is a reach.
"First of all, these techniques are not diagnostic, they are descriptive," he says. "And they don't provide any clinical evidence of any kind of abnormality or pathology. What they show are minor differences between two groups."
And the existence of some differences is hardly surprising, he says.
"These methods are used to find differences that are associated with being left-handed or right-handed, male or female, low IQ [or] high IQ, whether you are a musician or not," he says. "They're all within the normal range."
And 12 of the workers had a history of concussion, which also could account for some of the differences.
The real importance of the study is in what it did not find, Fields says.
"If there'd been brain injury, that would have been evident on the clinical brain imaging studies that were done before," he says. "There was no evidence of any pathology, and these more sophisticated measures confirm that."
The State Department did not respond to requests for comment on the study.