Diplomats who sustained mysterious brain injuries while stationed in Cuba experienced a cluster of symptoms, including anxiety, mental fog and dizziness, that is more complex than previously reported, scientists said Wednesday.
The problem began in the fall of 2016, when diplomatic personnel residing in Havana began to complain of ear pain after reporting hearing a high frequency noise, or sometimes a feeling of pressure in the ears, which followed them throughout a room.
In September 2017, the United States blamed Havana for failing to protect its diplomats and withdrew more than half its staff from the embassy while expelling 15 Cuban diplomats from Washington.
The new study by experts at the University of Miami and the University of Pittsburgh, published in the journal Laryngoscope Investigative Otolaryngology, did not solve the mystery or assign blame.
But it found "measurable, quantifiable evidence that something really did happen. It is not just hysteria," said Carey Balaban, professor of otolaryngology at the University of Pittsburgh School of Medicine.
"We don't know what they were exposed to and we certainly can't make any inferences as to whether it was deliberate or inadvertent."
The symptoms of 25 people were studied in the "acute phase," meaning shortly after diplomats fell ill but before they were diagnosed, the experts said.
The report details a range of symptoms that go beyond the description of elusive brain trauma, similar to a concussion without evidence of a physical impact, described by University of Pennsylvania researchers in February in the Journal of the American Medical Association.
The JAMA study extended longer, following the patients for months, but also gave no concrete cause for their ailments.
"We actually saw these individuals before formal diagnosis," Bonnie Levin, a professor of neurology at the University of Miami Miller School of Medicine, told reporters.
Their first complaints were "dizziness and disorientation" along with hearing concerns.
However, "standard clinical hearing tests did not reveal hearing loss except for in two individuals who were determined to have had pre-existing hearing loss prior to coming to our clinic," she said.
The patients did have abnormalities in balance, suggesting the inner ear was affected.
They also commonly reported feeling as if in a "cognitive fog. Something wasn't right. They felt off. They felt unbalanced in their thinking," she said.
- Not 'hysteria' -
Other emotional concerns included anxiety and irritability, trouble regulating emotions, feeling ups and downs, moodiness, low frustration tolerance and difficulty paying attention and staying on task.
When it came to performing complex tasks, patients found their working memory was not what it had been before.
Researchers declined to speculate on what caused the symptoms, but said their tests ruled out any possibility that the symptoms were made up.
"These individuals' symptoms were not random, were not isolated and actually fit together," Levin said.
"We don't understand the exact source but we do believe that there is a common neurocircuitry or anatomic pathway that underlies this particular constellation of events which involves vestibular, cognitive and emotional changes."
The researchers also gave no updates on the current health of those affected.
Prior media reports have raised the possibility of microwave weapons, sonic attacks, electromagnetic pulses and other forms of directed energy.
Balaban noted that there are a number of off-the-shelf pest control devices for home use that emit ultrasounds and electromagnetic pulses in the safe range for humans.
"It shows you that the technology is there -- and could be placed inside a room -- that could do such a thing," he said.
"The possible sources and medical science we have here do not lead to any quick and easy solution. I wish someone could tell us that right now."