Study: US personnel suffered 'symptoms resembling brain injury' in Cuba

21 workers sought medical attention

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The U.S. Embassy along Malecon Seaside Avenue in Havana, Cuba, on Aug. 12, 2015.

(CNN) - Doctors remain baffled by concussion-like symptoms that manifested in US government personnel while they were on assignment in Havana, Cuba. Their findings are laid out in a comprehensive medical report published Wednesday on what they found when they examined the patients. CNN first reported on the "acoustic attacks" in August.

According to the study, published in the medical journal JAMA, 21 workers sought medical attention beginning in late 2016 after suspected exposure to "auditory and sensory phenomena in their homes or hotel rooms."

The 10 men and 11 women reported hearing sounds including "buzzing," "grinding metal," "piercing squeals" and "humming."

"The sounds were often associated with pressurelike or vibratory sensory stimuli," according to the report. "The sensory stimuli were likened to air 'baffling' inside a moving car with the windows partially rolled down."

Doctors at the University of Pennsylvania, who authored the study and treated some of the personnel, said "individuals reported a similar constellation of neurological symptoms resembling brain injury." In other words, they suffered symptoms of concussion without having a head injury.

More specifically, the patients reported problems with cognition, balance, eyesight, hearing, sleeping and headaches. More than half needed to be prescribed medication in order to sleep or to deal with headaches. Many were, at least for a period of time, unable to return to work.

The report found "audible or sensory phenomena" were from an unknown source but came from a specified direction. In conclusion, the authors say their study raises "concern about a new mechanism for possible acquired brain injury from an exposure of unknown origin."

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