MIAMI — The American government employees in Cuba who suffered mystifying symptoms — dizziness, insomnia, difficulty concentrating — after hearing a strange high-pitched sound all had one thing in common: damage to the part of the inner ear responsible for balance, according to the first doctors to examine them after the episodes.
Two years after Americans posted at the United States Embassy in Havana began experiencing the peculiar phenomenon, doctors at the University of Miami on Wednesday published a scientific paper that confirms what these patients have said all along: Their condition is real, not the result of mass hysteria, a response to intense news media coverage or a stress reaction to being evacuated, as doctors in Cuba suggested.
“These people were injured,” said Dr. Michael E. Hoffer, the director of the university’s Vestibular and Balance Program and lead author of the study. “We’re not sure how. The injury resulted in ear damage and some trouble thinking.”
To some of the 26 people affected, the episode felt like something out of “Star Trek”: A few minutes of a high-pitched noise, often accompanied by a high-pressure sensation described as a “force field” felt in their homes and hotel rooms in Cuba over several months starting in late 2016, changed their lives and in some cases, ended careers.
The dizziness and cognitive problems that followed — including severe insomnia and nausea when using a computer — were so intense that at least one State Department employee went into early retirement this year. Another person who experienced the phenomenon in China went on leave. The State Department would not say how many others had returned to work.
Identifying the specific nature of the damage means that the patients can potentially be treated with physical therapy, the doctors said. It isn’t clear yet whether the injury is permanent.
The study, published in the journal Laryngoscope Investigative Otolaryngology, is the first to document the earliest symptoms of a medical mystery that started in Cuba, damaging relations between that country and the United States, and may have spread to China. Doctors found that all of the people affected by what was initially — and inaccurately — thought to be an acoustic attack had damage to the otolith, the organ that manages balance and the sensation of gravity.
The doctors found that it was unlikely that the affected diplomats and C.I.A. officers had suffered traumatic brain injuries. An earlier study from the University of Pennsylvania suggested that the patients showed signs of traumatic brain injury without ever experiencing a concussion.
The authors of the University of Miami report said theirs was the only study to document the medical examinations that took place soon after the sounds were heard, before news media reports or workers’ compensation claims could have affected results. The study does not offer any theory as to what caused the injuries, but Dr. Hoffer said he now felt confident that doctors can screen for the condition — and treat it.
He said the patients had described a sensation like a “force field” that they could physically feel. Some prolonged their exposure by walking around in search of the source. When they opened their front doors, it was gone, they told him.
“Their theory is that they were targeted, because they were being followed and the other individuals in their household were in some cases not affected,” Dr. Hoffer said.
“What we noticed is universal damage to the gravity organs in the ear,” he said. “The ear has a bunch of different balance organs — and two of them are gravity organs — and those are damaged in everyone.”
After suffering the damage, the patients’ bodies spend so much energy trying to stay balanced that it wipes them out, he said.
“That’s very fatiguing,” Dr. Hoffer said. “And it doesn’t leave a lot left over to remember where you put your keys.”
Dr. Bonnie E. Levin, the director neuropsychology at the University of Miami’s School of Medicine, examined a subset of the patients who had cognitive problems. The otherwise high-functioning people scored poorly on memory tests and other exams that measured their ability to multitask and hear information against background noise, she said.
“Everybody that I saw was quite disabled,” she said, adding that they also had trouble regulating emotion.
An investigation by the F.B.I. and other government agencies has so far not determined what caused the illnesses.
More than a year after the episodes began, the Trump administration sent the bulk of the embassy personnel home, leaving 18 people in Havana. Cubans who need visas to travel to the United States now have to go to Guyana to apply for them.
So far, 26 people posted in Havana have been identified with “otherwise-unexplained, medically-confirmed symptoms and clinical findings since the Department first became aware of these incidents in late 2016,” the State Department said in a statement.
In May, one person at the United States consulate in Guangzhou, China, “was determined to have a constellation of symptoms and findings similar to the affected U.S. government personnel and family members in Cuba.”
The government sent around 300 people posted in China for testing. Fifteen people needed further examinations, and one person had symptoms that required follow-up — although that case has not been officially linked to the same cause, the State Department said.
“Affected individuals have exhibited a range of health effects, including dizziness, headaches, balance problems, visual problems, cognitive problems, hearing loss, and other symptoms similar to those noted following concussion or minor traumatic brain injury,” the statement said. “Given the seeming exclusive focus on U.S. government personnel and their families in Havana, as well as the scope and duration of incidents, the Department has categorized the events in Havana as attacks. We cannot rule out that additional cases could come to light.”
Canada reported similar cases affecting several of its diplomats in Cuba.
Mark S. Zaid, a Washington lawyer who is representing about 11 of the Americans, said the Trump administration had not been forthcoming about its findings, and seemed to resist the notion that the person in China is suffering from the same illness.
“I think they know far more than what they have revealed,” he said.
The going theory, he said, is that some kind of microwave-based weapon is to blame.
The University of Miami study said “it would be imprudent to exclude any potential directed or non-directed energy sources at this time.”
Carlos Fernández de Cossio, the director of the United States Department at the Cuban Foreign Ministry, said the United States government had not made the patients or their medical histories available to Cuban experts.
“The way in which the government of the United States has dealt with this matter of the supposed health damages is worrisome,” he told the Cuban state-run media. “They have tackled it from the beginning with a high dose of political manipulation.”
Informed of the study’s findings, Mr. Zaid, the lawyer, said the University of Miami had confirmed what the patients were saying from the start.
“The key thing is that it appears testable,” he said.
He said none of his clients were feeling entirely better. One young woman recently took a leave of absence from work.
The woman who recently retired felt that the study validated the embassy employees, who were not always taken seriously, particularly if they were older or female, she said.
The situation, Mr. Zaid said, “has been very frustrating to the employees.”