MR Brain scans of 40 U.S. personnel who developed neurological symptoms following exposure to an unknown source in Cuba depict a number of differences in brain tissue and connectivity, compared to healthy subjects, according to a new study.

Researchers at the University of Pennsylvania Perelman School of Medicine have found that the symptoms are similar to those of persistent concussion syndrome, despite none of the patients showing signs of blunt head trauma.

"The areas implicated in the patients' brains, namely the cerebellum as well as the visuospatial and auditory networks, align with the neurological symptoms that were observed in the patients," said lead author Ragini Verma, a professor of radiology and head of the DiCIPHR (Diffusion and Connectomics in Precision Healthcare Research) imaging lab at Penn, in a statement. "These differences persisted even when people with some history of brain injury were excluded from the analysis."
The personnel, who served and lived in Havana, Cuba, began reporting difficulties in 2016, along with their family members, complaining of difficulties in concentration and memory, dizziness, visual issues and balance problems. The symptoms were connected to sudden, intensely loud noises heard in their homes and hotel rooms, the specifics of which remain unsolved. State Department officials referred to the event as a “sonic attack” or “directional phenomena”.

Researchers at Penn’s Center for Brain Injury and Repair for evaluation, treatment and rehabilitation studied the neurological symptoms of 21 patients who
reported exposure to the event, and later published their findings in 2018.

They also conducted a retrospective analysis using multimodal MR imaging on patients before they received any comprehensive rehabilitation treatment. The study compared their brains to that of 48 healthy individuals who were not exposed and displayed no symptoms, and used various computational tools to examine structural, diffusion and functional MR images. Patients exposed to the phenomena were found to have reduced white matter, a pattern of differences in measures of water diffusion in the tissue, and lower functional connectivity in the visuospatial and auditory subnetworks. Differences were found in the cerebellum, the part of the brain which control voluntary tasks, such as walking and writing.

The pattern of differences does not align with the pathological findings of any other imaging-based investigations for conditions like concussion and traumatic brain injury. Verma says a multimodal investigation is necessary to gain better understanding of the injury incurred by the patients and determine if a form of treatment is necessary or exists to address it.

"It's hard to tell where the problem started; the brain differences observed could be an immediate effect of the brain injury, or it could a compensatory effect of the recovery process," she said. "It's very difficult to say, especially with a retrospective, heterogeneous study, where people were included at various times after potential exposure. The important thing is that we did see differences at the group level."

The findings of the group-based analysis of the 40 patients were published in the journal, JAMA.

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