Havana Syndrome

Original Editor - Ahmed M Diab

Top Contributors - Ahmed M Diab, Ewa Jaraczewska, Lucinda hampton and Kim Jackson  

Introduction

In 2016, United States diplomats in Havana began to report unusual sensory and auditory stimuli, as well as dizziness, tinnitus, and other cognitive manifestations. A 6-7 month follow-up revealed persistent abnormalities in the cognitive, vestibular, and oculomotor domains. The variety of presenting symptoms made diagnosis difficult, so many theorised about the origin of the injury. Later, the Canadian diplomats and their families stationed in Havana described a similar set of symptoms.

Aetiology

The primary cause of these changes is unknown, and unravelling this mystery will necessitate additional research into the association between neural effects and symptoms. However, one study suggested that these symptoms were caused by acquired neurotoxicity. As a result, overexposure to cholinesterase inhibitors is hypothesised to be a possible cause.

Magnetic Resonance Imaging (MRI) findings

Both US and Canadian participants had neuroimaging abnormalities associated with their existence in Havana. In the United States, researchers discovered variances in grey and white matter (WM) volume, cerebellar diffusion properties, and functional network connectivity.

The findings show a decrease in white matter fibre density and network structural connectivity in Canadians who spent more than a month in Havana between 2016 and 2018. Microstructural changes in the fornix (a triangular area of white matter in the mammalian brain between the hippocampus and the hypothalamus) were discovered using advanced diffusion-weighted imaging techniques (diffusion magenetic resonance imaging), which corresponded to headaches and tinnitus. There are also microstructural changes in the splenium (the thick posterior part of the corpus callosum of the brain), which have been linked to headaches and fatigue. Furthermore, there is evidence of disrupted structural network connectivity in commissural thalamic and hippocampal projections to the brain's posterior regions. The precise reason for the observed white matter differences is unknown.

Resources

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