Cerebral diffusion and perfusion deficits in North Sea divers

Background: Diving is associated with a risk of cerebral decompression illness, and the prevalence of neurological symptoms is higher in divers compared with control groups. Microvascular dysfunction due to gas microembolism and exposure to hyperoxia are possible mechanisms, which may result in cerebral diffusion and perfusion deficits. Purpose: To investigate if possible functional derangements of the microvasculature and microstructure would be more prevalent among symptomatic divers. Material and Methods: Magnetic resonance imaging (MRI) was performed in 91 former divers and 45 controls. Individual parametric images of apparent diffusion coefficient (ADC), cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) were generated on the basis of diffusion-and perfusion-weighted imaging. To identify regions with statistically significant differences between groups (P < 0.05, corrected for false discovery rate), voxel-wise ANCOVA analysis was performed for each of the four parametric images. Results: Significant regional group differences were found in all four parametric comparisons. Gross regional ADC differences were seen throughout the brain, including large frontal and temporal white-matter regions, the hippocampus, and parts of the cerebellum. Differences in the perfusion maps were localized in fewer and smaller clusters, including parts of the cerebellum, the putamen, and the anterior watershed regions. Conclusion: Regional functional abnormalities as measured by diffusion-and perfusion-weighted imaging were identified in the divers, and there was a partial co-localization of the regions identified in the perfusion and the diffusion images. The findings may explain some of the long-term clinical symptoms reported among professional divers.