Abstract
A large proportion of lowlanders ascending to high-altitude (HA) show no signs of mountain sickness. Whether their brains have indeed suffered from HA environment and the persistent sequelae after return to lowland remain unknown. Thirty-one sea-level college students, who had a 30-day teaching on Qinghai-Tibet plateau underwent MRI scans before, during, and two months after HA exposure. Brain volume, cortical structures, and white matter microstructure were measured. Besides, serum neuron-specific enolase (NSE), C-reactive protein, and interleukin-6 and neuropsychiatric behaviors were tested. After 30-day HA exposure, the gray and white matter volumes and cortical surface areas significantly increased, with cortical thicknesses and curvatures changed in a wide spread regions; Anisotropy decreased with diffusivities increased in multiple sites of white matter tracts. Two months after HA exposure, cortical measurements returned to basal level. However, increased anisotropy with decreased diffusivities was observed. Behaviors and serum inflammatory factor did not significant changed during three time-point tests. NSE significantly decreased during HA but increased after HA exposure. Results suggest brain swelling occurred in people without neurological signs at HA, but no negative sequelae in cortical structures and neuropsychiatric functions were left after the return to lowlands. Reoxygenation changed white matter microstructure.
Highlights
Current neurologic data were mainly obtained from studies on mountain climbers ascending to extreme altitudes and developing acute mountain sickness (AMS)
SIENA has been extended to a single time-point method (Structural Image Evaluation, Using Normalization, of Atrophy Cross-sectional, SIENAX)[18], which provides global normalized brain volume (NBV), gray matter volume (GMV), and white matter volume (WMV)
Tract-Based Spatial Statistics (TBSS) approach was used to examine white matter (WM) fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) which are associated with local cerebral edema[13]
Summary
Current neurologic data were mainly obtained from studies on mountain climbers ascending to extreme altitudes and developing acute mountain sickness (AMS). Among these climbers, some showed cerebral edema, microhemorrhage, cortical atrophy, and cortical and subcortical lesions[6,7,8,9], while a small group did not display any changes in the brains[10,11]. The previous two studies were case-comparison and small reports; the images were obtained several days after the subjects’ return to the lowlands and the brain structure could have been influenced by hypoxia/reoxygenation-induced changes of cerebral blood flow[15]. We measured serum IL-6 and CRP, as their upregulation could be responsible for the brain changes
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