Investigation of Brain Impairment Using Diffusion-Weighted and Diffusion Tensor Magnetic Resonance Imaging in Experienced Healthy Divers.

BACKGROUND The aim of this study was to understand the changes of decompression illness in healthy divers by comparing diffusion-weighted (DWI) and diffusion tensor MRI findings among healthy professional divers and healthy non-divers with no history of diving. MATERIAL AND METHODS A total of 26 people were recruited in this prospective study: 11 experienced divers with no history of neurological decompression disease (cohort) and 15 healthy non-divers (control). In all study subjects, we evaluated apparent diffusion coefficient (ADC) and type of diffusion tensor metric fractional anisotropy (FA) values of different brain locations (e.g., frontal and parieto-occipital white matter, hippocampus, globus pallidus, putamen, internal capsule, thalamus, cerebral peduncle, pons, cerebellum, and corpus callosum). RESULTS ADC values of hippocampus were high in divers but low in the control group; FA values of globus pallidus and putamen were lower in divers compared to the control group. DWI depicted possible changes due to hypoxia in different regions of the brain. Statistically significant differences in ADC values were found in hypoxia, particularly in the hippocampus (p=0.0002), while FA values in the globus pallidus and putamen were statistically significant (p=0.015 and p=0.031, respectively). We detected forgetfulness in 6 divers and deterioration in fine-motor skills in 2 divers (p=0.002 and p=0.17, respectively). All of them were examined using neuro-psychometric tests. CONCLUSIONS Repeated hyperbaric exposure increases the risk of white matter damage in experienced healthy divers without neurological decompression illness. The hippocampus, globus pallidus, and putamen are the brain areas responsible for memory, learning, navigation, and fine-motor skills and are sensitive to repeated hyperbaric exposure.