U.S. diplomats who fell ill in Cuba are victims of a new neurological syndrome, according to brain researchers at the University of Pennsylvania (UPenn). But the team was unable to shed light on the malady’s mysterious cause, which the U.S. Department of State has characterized as a “health attack.”
From late 2016 through August 2017, as many as 24 U.S. citizens affiliated with the U.S. Embassy in Havana reported symptoms ranging from vertigo and sleeplessness to cognitive impairment. Many described hearing loud or disconcerting sounds before the onset of symptoms, or pressure sensations in their ears akin to the baffling that occurs in a moving car with the windows cracked open. “They felt something weird going on,” and when they moved away from the perceived exposure, some of “the symptoms abated,” says Douglas Smith, director of UPenn’s Center for Brain Injury and Repair. The State Department called in the UPenn group after initial examinations of diplomats at the University of Miami in Florida revealed persistent and inexplicable symptoms. The UPenn team’s report on the diplomats’ health appears in today’s issue of The Journal of the American Medical Association (JAMA).
The coincidence of the diplomats’ impairment and the auditory phenomena fueled speculation they were victims of a “sonic attack.” Last summer, citing what it saw as Cuba’s inability to protect U.S. diplomats, the State Department pulled most of its personnel out of Cuba and expelled from the United States a corresponding number of Cuban diplomats. The Cuban government has denied knowledge of an attack and has cooperated with the U.S. investigation, which is being spearheaded by the Federal Bureau of Investigation.
In December 2017, a panel of Cuban scientists evaluating limited medical information and sound recordings provided by U.S. investigators concluded that the likeliest explanation of the disparate symptoms in most of the diplomats is mass psychogenic illness—a conclusion shared by some U.S. neuroscientists. The Cuban experts also found that the frequency of a grating sound in the recordings they analyzed matched the chirping of the Jamaican field cricket.
Smith says it’s “premature” to conclude that the diplomats were attacked. But he and his colleagues believe an as-yet-unidentified exposure triggered a “constellation” of neurological symptoms consistent with a concussion—or as Smith puts it, “a concussion without an impact.”
Although what happens to the concussed brain remains murky, researchers say the brain’s network of connections often appears perturbed, perhaps because of temporary damage to the axons that connect nerve cells. A concussion’s symptoms include slower mental processing speeds and memory loss, says Smith, whose team noted such deficits in 17 of the 21 patients they studied. “It’s not that any patient can’t do a given task, but it requires way more effort,” co-author Randel Swanson, a brain injury rehabilitation specialist at UPenn, stated in an accompanying news article in JAMA. The U.S. personnel, the UPenn team concludes in the new paper, “appeared to have sustained injury to widespread brain networks without an associated history of head trauma.”
MRI scans of the U.S. personnel were largely normal, apart from three individuals with nonspecific abnormalities in their white matter—the axons that link nerve cells—that appear to be unrelated to the new syndrome, Smith says. The clear scans are not surprising, he says, because standard MRIs generally don’t reveal signs of a concussion. Rather, damage to the brain’s connections is picked up by a finer-grained MRI technique, diffusion tensor imaging (DTI). The UPenn team is planning to conduct DTI scans of the diplomats. Any connectivity damage should still be visible, Smith says, because DTI scans can pick up such abnormalities months or even years after a concussion.
The UPenn investigators discount psychogenic illness as an explanation. The U.S. personnel “weren’t all together,” Smith says, so his team believes some patients developed symptoms without knowledge that others were affected. And the deficits in eye movement and balance they measured in some diplomats are objective evidence of damage, Smith adds. “You couldn’t fake those tests.”
Others are not ready to dismiss psychogenic illness as a factor. In an accompanying editorial in JAMA, Christopher Muth, a neurologist at Rush University Medical Center in Chicago, Illinois, and Steven Lewis, a neurologist at Lehigh Valley Health Network in Allentown, Pennsylvania, point out that the UPenn team evaluated the diplomats on average 203 days after onset of symptoms. Therefore “it remains unclear whether individuals who developed symptoms were aware of the previous reports of others.” Cuban panel member Mitchell Valdés-Sosa, director of the Cuban Neurosciences Center in Havana, emphasizes that the panel “did not deny that some of the diplomats are ill … nor do we believe that mass psychogenic illness is the only explanation.” Rather, he says, psychogenic illness “could act as an amplifier causing more individuals to feel ill, and could explain many of the subjective complaints.” Valdés-Sosa also asserts that many of the reported symptoms could be attributable to pre-existing conditions.
In their editorial, Muth and Lewis conclude that “a unifying explanation for the symptoms … remains elusive.” Valdés-Sosa concurs on that point—as does the UPenn team.
But Smith and his colleagues are convinced that the cases are a cluster, and are working with the U.S. Centers for Disease Control and Prevention in Atlanta to further probe what they maintain is a new condition. One urgent task, Smith says, is defining the syndrome’s criteria. That will be important for evaluating any future cases, including U.S. civilians who visited Cuba and have since contacted the UPenn team claiming to have suffered similar symptoms.