Diplomats representing the United States have reported with unusual neurologic symptoms and MRI changes after being posted in Havana, Cuba between late 2016 to 2018. Here we examined white matter microstructure and network connectivity of individuals stationed in Havana, using diffusion-weighted MRI, fixel-based analysis, and structural connectomics as implemented in MRtrix3. MRI data acquisition and clinical assessments were done in a total of 24 diplomats and their family members and 40 healthy controls. The diplomat data was grouped into an exposed cohort (n = 16) and an unexposed cohort (n = 10), and among these, 2 individuals were assessed before and after potential exposure. Fixel-based analysis revealed a reduction in fiber density in two specific regions: the fornix and the splenium, in exposed individuals, relative to unexposed individuals and healthy controls. Post-hoc analyses showed the effect remained present (p < 0.05) in both regions when comparing exposed and unexposed diplomats; and reduced fibre density was correlated with longer time period stationed in Cuba after age-correction. Reduction of fibre density was also found to be linked with clinical symptoms of persistent migraine, tinnitus, sound sensitivity and fatigue. Network statistical comparisons revealed decreased structural connectivity in two distinct networks, comprising subcortical and cortical systems in exposed individuals, relative to unexposed and normative data. While the cause for the differences between the groups remains unknown, our results reveal region-specific white matter injury that is significantly correlated with clinical symptoms.