The most specific finding to date about physical damage from the attacks shows that whatever it was that harmed the Americans, it led to perceptible changes in their brains. It is one of several factors fuelling growing scepticism that some kind of sonic weapon was involved.
Medical testing has revealed the embassy workers developed changes to the white matter tracts that let different parts of the brain communicate, several US officials said, describing a growing consensus held by university and government physicians researching the attacks. White matter acts like information highways between brain cells.
Loud, mysterious sounds followed by hearing loss and ear-ringing had led investigators to suspect “sonic attacks”. But officials are now avoiding that term. The sounds may have been the byproduct of something else that caused damage, said three US officials briefed on the investigation.
Physicians, FBI investigators and US intelligence agencies have spent months trying to piece together the puzzle in Havana, where the US says 24 government officials and spouses fell ill, starting last year in homes and later in some hotels. The US refers to “specific attacks” but says it does not know who is behind them. A few Canadian embassy staffers also got sick.
Doctors still do not know how victims ended up with the white matter changes, or how exactly those changes might relate to their symptoms. US officials would not say whether the changes were found in all 24 patients.
Acoustic waves have never been shown to alter the brain’s white matter tracts, said Elisa Konofagou, a biomedical engineering professor at Columbia University who is not involved in the government’s investigation.
“I would be very surprised,” Konofagou said, adding that ultrasound in the brain is used frequently in modern medicine. “We never see white matter tract problems.”
Cuba has denied involvement, and calls the Trump administration’s claims that US workers were attacked “deliberate lies”. The new medical details may help the US counter Havana’s complaint that Washington has not presented any evidence.
The case has plunged the US medical community into uncharted territory. Physicians are treating the symptoms like a never-before-seen illness. After extensive testing and trial therapies, they are developing the first protocols to screen cases and identify the best treatments – even as the FBI investigation struggles to identify a culprit, method and motive.
The AP first reported in August that US workers had said they heard sounds that were audible in parts of rooms but inaudible just a few feet away – unlike normal sound, which disperses in all directions. Doctors have now come up with a term for such incidents: “directional acoustic phenomena”.
Most patients have fully recovered, some after rehabilitation and other treatment, officials said. Many are back at work. About a quarter had symptoms that persisted for long periods or remain to this day.
This year, the US said doctors found patients had had concussions, known as mild traumatic brain injury, but were uncertain beyond that what had happened in their brains. Concussions are often diagnosed based solely on symptoms.
As Cuba works to limit damage to its reputation and economy, its government has produced TV specials and an online summit about its own investigation. Cuba’s experts have concluded that the US allegations are scientifically impossible.
The Cubans have urged Washington to release information about what it has found. FBI investigators have spent months comparing cases to pinpoint what factors overlap.
The US has not identified any specific precautions it believes can mitigate the risk for diplomats in Havana, three officials have said, although an attack has not been reported since late August.
Since the embassy workers started falling ill last year, the state department has adopted a new protocol for workers before they go to Cuba that includes blood work and other “baseline” tests. If they later show symptoms, doctors can retest and compare.
Doctors still do not know the long-term medical consequences and expect that epidemiologists, who track disease patterns in populations, will monitor the 24 Americans for life.
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