US diplomats suffered mysterious brain damage and hearing loss in Cuba — and it could mean there's new way to cause brain injuries

No one knows exactly what caused the strange symptoms U.S. diplomats in Cuba experienced after they reported hearing strange noises that some have linked to "sonic attacks."

But a new study of the victims of these mysterious phenomena suggests a new, disconcerting possibility: Some unknown force projected in the direction of the patients could have somehow injured their brains.

"The unique circumstances of these patients and the consistency of the clinical manifestations raised concern for a novel mechanism of a possible acquired brain injury from a directional exposure of undetermined etiology," the study's authors wrote.

The saga began in late 2016 when American diplomatic staff (and some Canadians) that had been in Cuba began to report odd physical and mental symptoms. Some could no longer remember words, while others had hearing loss, speech problems, balance issues, nervous-system damage, headaches, ringing in the ears, and nausea.

Some even showed signs of brain swelling or concussions — mild traumatic brain injuries.

Many of the victims remember strange occurrences before the symptoms appeared, though others didn't hear or feel anything. One diplomat reported a "blaring, grinding noise" that woke him from his bed in a Havana hotel, according to the Associated Press. The AP also reported that some heard a "loud ringing or a high-pitch chirping similar to crickets or cicadas" in short bursts at night, while others said they could walk "in" and "out" of blaring noises that were audible only in certain spots.

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People walk past the U.S. Embassy in Havana, Cuba, June 19, 2017. REUTERS/Alexandre Meneghini
A tour bus of Transgaviota drives past the U.S. embassy in Havana, Cuba June 13, 2017. Picture taken June 13, 2017. REUTERS/Stringer
An exterior view of the U.S. Embassy is seen in Havana, Cuba, June 19, 2017. REUTERS/Alexandre Meneghini
People wait in line to enter the U.S. Embassy in Havana, Cuba, April 20, 2017. Picture taken April 20, 2017. REUTERS/Alexandre Meneghini
People wait to enter the U.S. Embassy in Havana, Cuba, April 20, 2017. Picture taken April 20, 2017. REUTERS/Alexandre Meneghini
A vintage car passes by in front of the U.S. Embassy in Havana, Cuba, January 12, 2017. REUTERS/Alexandre Meneghini
Cuban flags fly near U.S flag beside the U.S embassy in Havana December 31, 2015. REUTERS/Enrique de la Osa
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Flagposts installed outside the U.S. embassy cast their shadows on the sidewalk of the seafront Malecon in Havana, December 18, 2015. REUTERS/Alexandre Meneghini
Tourists pass by the U.S. Embassy in Havana, February 18, 2016. Picture taken February 18, 2016. REUTERS/Alexandre Meneghini
Competitors run past the U.S. embassy during the Marabana marathon in Havana, November 15, 2015. In the year since detente, more Americans are visiting Cuba, and more Cubans are trying to reach the U.S., concerned that special treatment for Cubans may end. While foreigners are in a frenzy, most Cubans report little change. Although they have guaranteed education and healthcare and minimal fear of violent crime, their wages are poor and economic opportunities limited. Picture taken November 15, 2015. REUTERS/Alexandre Meneghini
The Cuban flag flies at half staff in recognition of the death of Fidel Castro, the long time leader of Cuba, at the Cuban Embassy in Washington, U.S., November 28, 2016. REUTERS/Joshua Roberts
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The U.S. State Department eventually determined that the incidents were "specific attacks" and moved to cut its Cuban embassy staff by 60%.

But despite that determination, no one understands those "specific attacks" or is even sure they're responsible for everything that's happened. According to ProPublica, the FBI hasn't even been able to rule out the possibility that some of the patients were never attacked in the first place.

Studying the victims

Most of the victims were first examined in Miami, but a team of researchers from the University of Pennsylvania's Center for Brain Injury and Repair were selected to help further evaluate and treat at least 21 patients, whose cases are described in the new study.

By studying those 11 women and 10 men, the researchers were able to establish a significant amount of common ground among the patients. More than 80% reported hearing a sound that had a "directional" source — it seemed to come from somewhere. After three months, 81% still had cognitive issues, 71% had balance problems, 86% had vision issues, and about 70% still reported hearing problems and headaches.

The fact that a number of these symptoms could be subjective has raised questions about the possibility that this group of people is suffering from some sort of collective delusion, according to the study authors. But they say that mass delusion is unlikely, since affected individuals were all highly motivated and of a broad age distribution, factors that don't normally correspond with mass psychogenic illness. Plus, objective tests of ears and eye motion all revealed real clinical abnormalities.

All these symptoms seem consistent with some form of mild brain trauma, according to the researchers. But these symptoms persisted far longer than most concussion symptoms do, and were not associated with blunt head trauma.

"These individuals appeared to have sustained injury to widespread brain networks without an associated history of head trauma," the study authors wrote.

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A protester reacts as the U.S. Consulate in Benghazi is seen in flames during a protest by an armed group said to have been protesting a film being produced in the United States September 11, 2012. REUTERS/Esam Al-Fetori/File Photo
An exterior view of the U.S. consulate, which was attacked and set on fire by gunmen yesterday, in Benghazi September 12, 2012. Christopher Stevens, the U.S. ambassador to Libya, and three embassy staff were killed as they rushed away from the consulate building, stormed by al Qaeda-linked gunmen blaming America for a film that they said insulted the Prophet Mohammad. Stevens was trying to leave the consulate building for a safer location as part of an evacuation when gunmen launched an intense attack, apparently forcing security personnel to withdraw. REUTERS/Esam Al-Fetori (LIBYA - Tags: POLITICS CIVIL UNREST)
Christopher Stevens, the U.S. ambassador to Libya, smiles at his home in Tripoli June 28, 2012. Stevens and three embassy staff were killed late on September 11, 2012, as they rushed away from a consulate building in Benghazi, stormed by al Qaeda-linked gunmen blaming America for a film that they said insulted the Prophet Mohammad. Stevens was trying to leave the consulate building for a safer location as part of an evacuation when gunmen launched an intense attack, apparently forcing security personnel to withdraw. Picture taken June 28, 2012. REUTERS/Esam Al-Fetori (LIBYA - Tags: POLITICS CIVIL UNREST OBITUARY)
The U.S. Consulate in Benghazi is seen in flames during a protest by an armed group said to have been protesting a film being produced in the United States September 11, 2012. REUTERS/Esam Al-Fetori/File Photo
A man walks inside the U.S. consulate, which was attacked and set on fire by gunmen yesterday, in Benghazi September 12, 2012. Christopher Stevens, the U.S. ambassador to Libya, and three embassy staff were killed as they rushed away from the consulate building, stormed by al Qaeda-linked gunmen blaming America for a film that they said insulted the Prophet Mohammad. Stevens was trying to leave the consulate building for a safer location as part of an evacuation when gunmen launched an intense attack, apparently forcing security personnel to withdraw. REUTERS/Esam Al-Fetori (LIBYA - Tags: POLITICS CIVIL UNREST TPX IMAGES OF THE DAY)
The remains of the U.S. ambassador and three other Americans killed in an attack in Libya are taken off a transport aircraft during a return of remains ceremony at Andrews Air Force Base near Washington, September 14, 2012. Ambassador Christopher Stevens and the other Americans died after gunmen attacked the lightly fortified U.S. consulate and a safe house refuge in Benghazi on Tuesday night. REUTERS/Jason Reed (UNITED STATES - Tags: POLITICS) BEST QUALITY AVAILABLE
The U.S. Consulate in Benghazi is seen in flames during a protest by an armed group said to have been protesting a film being produced in the United States September 11, 2012. An American staff member of the U.S. consulate in the eastern Libyan city of Benghazi has died following fierce clashes at the compound, Libyan security sources said on Wednesday. Armed gunmen attacked the compound on Tuesday evening, clashing with Libyan security forces before the latter withdrew as they came under heavy fire. REUTERS/Esam Al-Fetori (LIBYA - Tags: POLITICS CIVIL UNREST)
(L-R) Tom Stevens, Anne Stevens, M.D., and Hilary Stevens Koziol, M.D., siblings of slain U.S. Ambassador to Libya Christopher Stevens, speak during a public memorial service in San Francisco, California October 16, 2012. Hundreds of mourners are expected to fill a marble rotunda in San Francisco's City Hall on Tuesday for a public memorial to Stevens, who was killed along with three other American embassy staff in a militant attack on the U.S. mission in Benghazi, Libya last month. REUTERS/Stephen Lam (UNITED STATES - Tags: POLITICS OBITUARY)
The U.S. Consulate in Benghazi is seen in flames during a protest by an armed group said to have been protesting a film being produced in the United States September 11, 2012. An American staff member of the U.S. consulate in the eastern Libyan city of Benghazi has died following fierce clashes at the compound, Libyan security sources said on Wednesday. Armed gunmen attacked the compound on Tuesday evening, clashing with Libyan security forces before the latter withdrew as they came under heavy fire. REUTERS/Esam Al-Fetori (LIBYA - Tags: POLITICS CIVIL UNREST)
U.S. Secretary of State Hillary Clinton testifies on the September attacks on U.S. diplomatic sites in Benghazi, Libya, during a Senate Foreign Relations Committee hearing on Capitol Hill in Washington January 23, 2013. REUTERS/Kevin Lamarque (UNITED STATES - Tags: POLITICS CIVIL UNREST)
The U.S. Consulate in Benghazi is seen in flames during a protest by an armed group said to have been protesting a film being produced in the United States September 11, 2012. An American staff member of the U.S. consulate in the eastern Libyan city of Benghazi has died following fierce clashes at the compound, Libyan security sources said on Wednesday. Armed gunmen attacked the compound on Tuesday evening, clashing with Libyan security forces before the latter withdrew as they came under heavy fire. REUTERS/Esam Al-Fetori (LIBYA - Tags: POLITICS CIVIL UNREST)
The U.S. Consulate in Benghazi is seen in flames during a protest by an armed group said to have been protesting a film being produced in the United States September 11, 2012. An American staff member of the U.S. consulate in the eastern Libyan city of Benghazi has died following fierce clashes at the compound, Libyan security sources said on Wednesday. Armed gunmen attacked the compound on Tuesday evening, clashing with Libyan security forces before the latter withdrew as they came under heavy fire. REUTERS/Esam Al-Fetori (LIBYA - Tags: POLITICS CIVIL UNREST)
An interior view of the U.S. consulate, which was attacked and set on fire by gunmen yesterday, in Benghazi September 12, 2012. Christopher Stevens, the U.S. ambassador to Libya, and three embassy staff were killed as they rushed away from the consulate building, stormed by al Qaeda-linked gunmen blaming America for a film that they said insulted the Prophet Mohammad. Stevens was trying to leave the consulate building for a safer location as part of an evacuation when gunmen launched an intense attack, apparently forcing security personnel to withdraw. REUTERS/Esam Al-Fetori (LIBYA - Tags: POLITICS CIVIL UNREST TPX IMAGES OF THE DAY)
The U.S. Consulate in Benghazi is seen in flames during a protest by an armed group said to have been protesting a film being produced in the United States September 11, 2012. An American staff member of the U.S. consulate in the eastern Libyan city of Benghazi has died following fierce clashes at the compound, Libyan security sources said on Wednesday. Armed gunmen attacked the compound on Tuesday evening, clashing with Libyan security forces before the latter withdrew as they came under heavy fire. REUTERS/Esam Al-Fetori (LIBYA - Tags: POLITICS CIVIL UNREST TPX IMAGES OF THE DAY)
The U.S. Consulate in Benghazi is seen in flames during a protest by an armed group said to have been protesting a film being produced in the United States September 11, 2012. An American staff member of the U.S. consulate in the eastern Libyan city of Benghazi has died following fierce clashes at the compound, Libyan security sources said on Wednesday. Armed gunmen attacked the compound on Tuesday evening, clashing with Libyan security forces before the latter withdrew as they came under heavy fire. REUTERS/Esam Al-Fetori (LIBYA - Tags: POLITICS CIVIL UNREST)
A mourner holds a program during a public memorial service for slain U.S. Ambassador to Libya Christopher Stevens in San Francisco, California October 16, 2012. Hundreds of mourners are expected to fill a marble rotunda in San Francisco's City Hall on Tuesday for a public memorial to Stevens, who was killed along with three other American embassy staff in a militant attack on the U.S. mission in Benghazi, Libya last month. REUTERS/Stephen Lam (UNITED STATES - Tags: POLITICS OBITUARY)
A burning car is seen at the U.S. Consulate in Benghazi during a protest by an armed group said to have been protesting a film being produced in the United States September 11, 2012. An American staff member of the U.S. consulate in the eastern Libyan city of Benghazi has died following fierce clashes at the compound, Libyan security sources said on Wednesday. Armed gunmen attacked the compound on Tuesday evening, clashing with Libyan security forces before the latter withdrew as they came under heavy fire. REUTERS/Esam Al-Fetori (LIBYA - Tags: POLITICS CIVIL UNREST)
Damage at the U.S. Consulate in Benghazi is seen during a protest by an armed group said to have been protesting a film being produced in the United States September 11, 2012. An American staff member of the U.S. consulate in the eastern Libyan city of Benghazi has died following fierce clashes at the compound, Libyan security sources said on Wednesday. Armed gunmen attacked the compound on Tuesday evening, clashing with Libyan security forces before the latter withdrew as they came under heavy fire. REUTERS/Esam Al-Fetori (LIBYA - Tags: POLITICS CIVIL UNREST)
The U.S. Consulate in Benghazi is seen in flames during a protest by an armed group said to have been protesting a film being produced in the United States September 11, 2012. An American staff member of the U.S. consulate in the eastern Libyan city of Benghazi has died following fierce clashes at the compound, Libyan security sources said on Wednesday. Armed gunmen attacked the compound on Tuesday evening, clashing with Libyan security forces before the latter withdrew as they came under heavy fire. REUTERS/Esam Al-Fetori (LIBYA - Tags: POLITICS CIVIL UNREST)
Damage at the U.S. Consulate in Benghazi is seen during a protest by an armed group said to have been protesting a film being produced in the United States September 11, 2012. An American staff member of the U.S. consulate in the eastern Libyan city of Benghazi has died following fierce clashes at the compound, Libyan security sources said on Wednesday. Armed gunmen attacked the compound on Tuesday evening, clashing with Libyan security forces before the latter withdrew as they came under heavy fire. REUTERS/Esam Al-Fetori (LIBYA - Tags: POLITICS CIVIL UNREST)
Cameras from news photographers surround a table before the arrival of U.S. Secretary of State Hillary Clinton to testify on the September attack on U.S. diplomatic sites in Benghazi, Libya, during a hearing held by the U.S. Senate Foreign Relations Committee on Capitol Hill in Washington January 23, 2013. REUTERS/Kevin Lamarque (UNITED STATES - Tags: POLITICS TPX IMAGES OF THE DAY)
An exterior view of the U.S. consulate, which was attacked and set on fire by gunmen yesterday, in Benghazi September 12, 2012. Christopher Stevens, the U.S. ambassador to Libya, and three embassy staff were killed as they rushed away from the consulate building, stormed by al Qaeda-linked gunmen blaming America for a film that they said insulted the Prophet Mohammad. Stevens was trying to leave the consulate building for a safer location as part of an evacuation when gunmen launched an intense attack, apparently forcing security personnel to withdraw. REUTERS/Esam Al-Fetori (LIBYA - Tags: POLITICS CIVIL UNREST)
An interior view of the damage at the U.S. consulate, which was attacked and set on fire by gunmen yesterday, in Benghazi September 12, 2012. Christopher Stevens, the U.S. ambassador to Libya, and three embassy staff were killed as they rushed away from the consulate building, stormed by al Qaeda-linked gunmen blaming America for a film that they said insulted the Prophet Mohammad. Stevens was trying to leave the consulate building for a safer location as part of an evacuation when gunmen launched an intense attack, apparently forcing security personnel to withdraw. REUTERS/Esam Al-Fetori (LIBYA - Tags: POLITICS CIVIL UNREST)
An interior view of the U.S. consulate, which was attacked and set on fire by gunmen yesterday, in Benghazi September 12, 2012. Christopher Stevens, the U.S. ambassador to Libya, and three embassy staff were killed as they rushed away from the consulate building, stormed by al Qaeda-linked gunmen blaming America for a film that they said insulted the Prophet Mohammad. Stevens was trying to leave the consulate building for a safer location as part of an evacuation when gunmen launched an intense attack, apparently forcing security personnel to withdraw. REUTERS/Esam Al-Fetori (LIBYA - Tags: POLITICS CIVIL UNREST)
U.S. Secretary of State Hillary Clinton (R) hugs Senator John McCain (R-AZ) as she arrives to testify on the September attack on U.S. diplomatic sites in Benghazi, Libya during a hearing held by the U.S. Senate Foreign Relations Committee on Capitol Hill in Washington January 23, 2013. REUTERS/Kevin Lamarque (UNITED STATES - Tags: POLITICS CIVIL UNREST)
People stand near a burnt car at the U.S. consulate, which was attacked and set on fire by gunmen yesterday, in Benghazi September 12, 2012. Christopher Stevens, the U.S. ambassador to Libya, and three embassy staff were killed as they rushed away from the consulate building, stormed by al Qaeda-linked gunmen blaming America for a film that they said insulted the Prophet Mohammad. Stevens was trying to leave the consulate building for a safer location as part of an evacuation when gunmen launched an intense attack, apparently forcing security personnel to withdraw. REUTERS/Esam Al-Fetori (LIBYA - Tags: POLITICS CIVIL UNREST)
White House staff are pictured after they lowered the U.S. flag to half staff on the roof of the White House in Washington September 12, 2012, following the death of U.S. Ambassador to Libya, Chris Stevens and others in Benghazi. Stevens and three embassy staff were killed in an attack on the Benghazi consulate and a safe house refuge, stormed by Islamist gunmen blaming America for a film they said insulted the Prophet Mohammad. REUTERS/Jason Reed (UNITED STATES - Tags: POLITICS CIVIL UNREST)
Patricia Smith, mother of Benghazi victim Sean Smith (pictured at right), addresses the Republican National Convention on July 18, 2016 at Quicken Loans Arena in Cleveland, Ohio. The Republican Party opened its national convention, kicking off a four-day political jamboree that will anoint billionaire Donald Trump as its presidential nominee. / AFP / Robyn BECK (Photo credit should read ROBYN BECK/AFP/Getty Images)
WASHINGTON, DC - SEPTEMBER 11: Jennifer Brandt holds signs during a 'Call to Action' rally held by various conservative organizations on the grounds of the U.S. Capitol, marking the one year anniversary of the attacks on the U.S. compound in Benghazi September 11, 2013 in Washington, DC. U.S. Ambassador Chris Stevens, Sean Smith, Glen Doherty and Tyrone Woods were all killed during the attacks last year. (Photo by Win McNamee/Getty Images)
MAY 27, 2013. SAN DIEGO, CA. Four WWII-era T-34 planes from the San Diego T-34 Performance Team fly over a crowd of about 2000 people gathered at the Mt. Soledad Veterans Memorial in San Diego, CA on Memorial Day, May 27, 2013. The ceremony honored former Navy SEAL members Glen Doherty and Tyrone Woods who were killed durng the attack on the U.S. consulate in Benghazi, Libya on 9/12/12. (Photo by Don Bartletti/Los Angeles Times via Getty Images)
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Mysterious weapons — or something else?

Despite having identified common symptoms and clinical evidence of some sort of injury, researchers are still at a loss about the cause.

If there is some kind of weapon involved, no one knows what kind it was or who would have used it. The Cuban government has denied any connection and investigators haven't found any link to Russia, which intelligence analysts had speculated might have the means and motivation to carry out an attack.

The reported presence of strange audio and of the feeling of changes in air pressure have led to speculation about some kind of sonic or audio-based weapon. But even though sonic weapons exist, they're very visible and easy to avoid, according to Seth Horowitz, a neuroscientist who wrote the book "The Universal Sense: How Hearing Shapes the Mind. Plus, the specific symptoms make that unlikely.

"There isn't an acoustic phenomenon in the world that would cause those type of symptoms," said Horowitz.

He speculated that perhaps some sort of mysterious pathogen or other phenomenon could have caused the symptoms, but the authors of the new study report that no signs infection (like fever) were identified. They determined it was unlikely a chemical agent would have caused these effects without damaging other organs.

In an editorial published alongside the new study, two doctors wrote that without more information and more data on the patients before they reported feeling ill, we can't be certain what went wrong.

"At this point, a unifying explanation for the symptoms experienced by the US government officials described in this case series remains elusive and the effect of possible exposure to audible phenomena is unclear," the editorial's authors wrote. "Going forward, it would be helpful for government employees traveling to Cuba to undergo baseline testing prior to deployment to allow for a more informed interpretation of abnormalities that might later be detected after a potential exposure."

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