Dec. 13 (UPI) -- Workers at the U.S. Embassy in Cuba have permanent inner ear damage after the mysterious sonic attacks in the building a year ago, a new study found.
The study found 25 Americans who worked at the embassy in Havana in 2016 and 2017 complained of hearing loss, dizziness, ear pain and vertigo. As a result, the affected individual would have mild cognitive issues and forgetfulness. Some report a ringing in their ear from tinnitus. The cause, they believe, was a high-frequency noise that followed them from room to room but stopped if they went outside.
Others reported a sensation of pressure passing through their head and abdomen in some parts of the room that wouldn't happen elsewhere.
The sonic attacks prompted the United States to recall 60 percent of its embassy staff. Fifteen diplomats were also ordered to leave the Cuban Embassy in Washington, D.C.
The study by the University of Miami's Miller School of Medicine and the University of Pittsburgh examined the workers at the embassy and compared them to roommates who didn't work at the facility.
"This is the first and only report of the acute presentation (seen shortly after exposure) in this unique group of patients," Dr. Michael E. Hoffer, a professor of otolaryngology and neurological surgery, said in the report. "Our findings are not biased or influenced by the effects of time, variable amounts of rehabilitation, workers compensation concerns or media attention."
Hoffer found that the inner ear had a unique pattern of "cognitive and behavioral dysfunction" among the people exposed to the sonic attack.
Neurology Professor Bonnie E. Levin said the findings will help with similar diagnoses in the future.
"Furthermore, careful documentation of the initial injury pattern is needed to develop effective preventative and treatment strategies," Levin said.
The report did not determine what caused the problem, noting that intense ultrasonic radiation can produce "a syndrome involving manifestations of nausea, headache, tinnitus, dizziness and fatigue."
"The exposure responsible for these findings is unknown," the authors said. "It would be imprudent to exclude any potential directed or non-directed energy sources at this time."