In the fall of 2016, American diplomats in Cuba began experiencing hearing loss, dizziness and cerebral edema.
According to the Associated Press, which first reported the incident in August 2017, some of the diplomats' symptoms were so severe that they were forced to return to the United States prematurely.
Most of the affected diplomats reported hearing strange noises in their homes and hotel rooms; a few days later, they developed headaches and hearing loss. CNN reported that some Canadian diplomats have also suffered from similar symptoms.
The incident puzzled the US State Department. After a thorough investigation, officials blamed a hidden sound device that had been deployed near diplomatic residences.
Although the Federal Bureau of Investigation ruled out this possibility almost five months after the allegations, the damage to US-Cuba relations was done.
The incident has left the recently restored diplomatic relations between the United States and Cuba very cold.
Cuban officials denied any involvement in this and issued a statement that said: "Cuba has never allowed or allowed Cuban territory to be used for any action against accredited diplomatic officials or their families, without any exceptions."
Despite this, the US expelled two Cuban diplomats from its embassy in Washington in response to the alleged attacks.
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Now, almost two years after the original incident, a new report from a group of researchers at the University of Pennsylvania published in the Journal of the American Medical Association (JAMA) sheds more light on this mystery and makes it even more mysterious.
The JAMA study found that diplomats not only experienced symptoms such as headaches, memory problems, and cerebral edema, but most importantly, they suffered a concussion without any traumatic external influences on the head.
The JAMA report, which examined 21 of the 24 US diplomats affected, confirmed that they suffered from "injuries to widespread areas of the brain not associated with head trauma."
Concussion without concussion
“Everyone who has seen these patients is convinced of this,” Douglas Smith, director of the Brain Injury and Repair Center at the University of Pennsylvania's Perelman School of Medicine and lead author of the study, told The New York Times.
Although the JAMA report does not clearly state that sonic weapons were used, Smith and colleagues explained that “sound in the sonic range (20 hertz to 20,000 hertz) is not known to cause permanent damage to the central nervous system, and therefore the injuries described are may have been associated with another form of exposure."
Other experts believe that no known sonic weapon causes the symptoms that diplomats have experienced.
By documenting and substantiating the extent of the injuries to American diplomats, the JAMA report adds even more intrigue, mystery and mystery to the Cuban incident. We still don't know who - or what - is the culprit for these unexplained tremors.
So what does the JAMA report give us?
The findings confirm that US diplomats did indeed suffer concussions without being hit on the head. But beyond that, we know nothing more than six months ago, when the incident was first learned.
The degree of brain injury to diplomats has been scientifically confirmed, but researchers still don't know what actually caused it.
It could be an unprecedented, unprecedented phenomenon, as the JAMA report says, or it could be a sonic weapon we can't even imagine.