'Sonic attacks' on U.S. government workers in Cuba changed victims' brain structure, study finds

(CNN)Whatever was behind the "sonic attacks" experienced by US government personnel in Havana, Cuba, starting in late 2016 remains a mystery -- but a new study published Tuesday looks inside the workers' brains for clues.

MRI brain scans from 40 patients -- 23 men and 17 women -- showed variations in brain structure and functional connectivity, which measures relationships among different brain regions, when compared with 48 other adults. The scans were taken between August 2017 to June 2018.

"There were group differences all over the brain," said study author Ragini Verma, professor of radiology and neurosurgery at University of Pennsylvania's Perelman School of Medicine. "Especially in an area called the cerebellum, which is also implicated in the kind of clinical symptoms that most of these patients were demonstrating, which is balance, eye movement, dizziness, etcetera."

Differences in connectivity were also observed in the brain's auditory and visuospatial areas, according to the study. However, the authors note that the clinical importance of these findings is uncertain, and they didn't have earlier MRIs of the patients to compare what their brains looked like before the incidents.

Moreover, these patterns don't fit a clear picture of a specific disorder, the authors say.

"It certainly does not resemble the imaging presentation of traumatic brain injury or concussion, although they present with clinical symptoms which are concussion-like," Verma said.

"It says something happened, and we need to look further, and that's about it."