Cerebral glucose metabolism 2 weeks following an 8000 m high altitude excursion

Introduction: Little is known of regional cerebral glucose metabolism (LCMRglu) following high altitude excursions. The purpose of this study was to evaluate LCMRglu following an 40 day high altitude excursion. Methods: The study was performed on 11 male mountaineers, mean age 31.36 y, range 27-36. The subjects climbed Mount Shisha Pangma in the Himalaya (8048 m), an excursion which lasted 43 days. The total duration above 6000 m was 18 days. 18F-FDG PET was performed before and 2 weeks after the excursion on a GE Advance scanner. A single 10 minute image was acquired 40 minutes following the injection of 70 MBq 18F-FDG. The scans were first transformed into stereotactic space and normalized to mean whole brain activity, then statistical parametric mapping (SPM) was performed to assess the change of LCMRglu. In addition a region of interest analysis was performed on the interesting structures identified by SPM. Results: Significant increases (corrected for multiple comparisons) of relative FDG uptake were found in cerebellum (Z=5.36, 7.6±7.0, mean±s.d. of percent increase) and the left thalamus (Z= 4.91, 8.2±3.2%). The right thalamus demonstrated a trend towards increased LCMRglu. Conclusion: There are circumscribed areas with an increase in glucose metabolism following exposure to high altitude. The physiological meaning of this finding is at present not clear. One could speculate that it represents a compensatory reaction to excessive hypoxic stress