US embassy in Cuba
© Alexandre Meneghini / Reuters
US embassy, Cuba
More than two dozen U.S. personnel appeared to have suffered "widespread brain network dysfunction" while working at the U.S. embassy in Cuba, according to a new medical report.

The Journal of the American Medical Association published a report Wednesday detailing what they call a "neurotrauma from a nonnatural source" experienced by Americans while in Havana.

According to the U.S. State Department, 24 Americans experienced these mysterious "health attacks" which has left medical officials baffled for more than a year now. After the incidents, the U.S. withdrew most of their diplomats and officials out of Havana.

The symptoms included trouble sleeping, visual problems, loss of concentration, headaches, tinnitus, and hearing loss. Three of the individuals who experienced hearing loss have since been fitted for hearing aids.

Of the 21 individuals studied by doctors at the University of Pennsylvania's Perelman School of Medicine, 18 reported hearing a loud, localized sound when they first arrived to their living arrangements, according to the report obtained by ABC News.

The sound, which was reportedly "directional, intensely loud, and with pure and sustained tonality," was described using terms such as "buzzing," "grinding metal," "piercing squeals," and "humming." Most agreed the noise was high-pitched and all agreed they experienced symptoms directly after hearing the noise.

At the time of the study, all the individuals had shown signs of improvement although 14 had not returned to work full-time due to their conditions.

The doctors have ruled out a virus or chemicals as the cause of the symptoms, however, they can't confirm if the noise phenomena is in any way related.

Details on the patients and their positions within the embassy have been withheld by the State Department for security concerns.