Abstract
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.
Acknowledgments
The authors would like to thank the radiographers Liv Mekki and Jarle Sæter, Department of Radiology, Haukeland University Hospital, Bergen, Norway, for carefully acquiring the imaging data in this study. The authors would also like to thank Associate Professor Lars Ersland, Department of Clinical Engineering, Haukeland University Hospital, Bergen, Norway and Professor Arvid Lundervold, Department of Biomedicine, University of Bergen for their valuable contribution to setting up the imaging protocol and initial data analysis. Furthermore, the authors are grateful to Bayer Schering Pharma, Germany, for supporting the study with the contrast agent Gadovist. The study was financed by a grant from the Norwegian Ministry of Health and Care Services.
Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.