Morphological Brain Changes after Climbing to Extreme Altitudes--A Prospective Cohort Study.
BACKGROUND
Findings of cerebral cortical atrophy, white matter lesions and microhemorrhages have been reported in high-altitude climbers. The aim of this study was to evaluate structural cerebral changes in a large cohort of climbers after an ascent to extreme altitudes and to correlate these findings with the severity of hypoxia and neurological signs during the climb.


METHODS
Magnetic resonance imaging (MRI) studies were performed in 38 mountaineers before and after participating in a high altitude (7126 m) climbing expedition. The imaging studies were assessed for occurrence of new WM hyperintensities and microhemorrhages. Changes of partial volume estimates of cerebrospinal fluid, grey matter, and white matter were evaluated by voxel-based morphometry. Arterial oxygen saturation and acute mountain sickness scores were recorded daily during the climb.


RESULTS
On post-expedition imaging no new white matter hyperintensities were observed. Compared to baseline testing, we observed a significant cerebrospinal fluid fraction increase (0.34% [95% CI 0.10-0.58], p = 0.006) and a white matter fraction reduction (-0.18% [95% CI -0.32--0.04], p = 0.012), whereas the grey matter fraction remained stable (0.16% [95% CI -0.46-0.13], p = 0.278). Post-expedition imaging revealed new microhemorrhages in 3 of 15 climbers reaching an altitude of over 7000 m. Affected climbers had significantly lower oxygen saturation values but not higher acute mountain sickness scores than climbers without microhemorrhages.


CONCLUSIONS
A single sojourn to extreme altitudes is not associated with development of focal white matter hyperintensities and grey matter atrophy but leads to a decrease in brain white matter fraction. Microhemorrhages indicative of substantial blood-brain barrier disruption occur in a significant number of climbers attaining extreme altitudes.
Institute for Diagnostic and Interventional Neuroradiology, University Hospital and University of Bern, 3010, Bern, Switzerland.
Raimund
R
Kottke
Department of Intensive Care Medicine, University Hospital and University of Bern, 3010, Bern, Switzerland.
Jacqueline
J
Pichler Hefti
Support Centre for Advanced Neuroimaging (SCAN), Institute for Diagnostic and Interventional Neuroradiology, University Hospital and University of Bern, 3010, Bern, Switzerland.
Christian
C
Rummel
Institute for Diagnostic and Interventional Neuroradiology, University Hospital and University of Bern, 3010, Bern, Switzerland.
Martinus
M
Hauf
Swiss Sport Clinic, 3014, Bern, Switzerland.
Urs
U
Hefti
Department of Intensive Care Medicine, University Hospital and University of Bern, 3010, Bern, Switzerland.
Tobias Michael
TM
Merz
D000531:Altitude; D000532:Altitude Sickness; D001921:Brain / Q000166:cytology*; D015331:Cohort Studies; D066128:Gray Matter / Q000166:cytology; D006801:Humans; D008279:Magnetic Resonance Imaging; D009051:Mountaineering; D011446:Prospective Studies