Quantitative EEG in acute mountain sickness

Objectives - To investigate if the EEG response at moderate altitude may pr edict a person's tolerance to acute mountain sickness (AMS). Materials and methods - Frequency analysis (QEEG) of tape-recorded ambulatory EEG was per formed in 6 climbers during a mountaineering expedition to 7546 m above sea level. The QEEG response in climbers, measured at sea level, at 4500 m, an d at 1800 m 1-4 days after maximal altitude exposure, was compared to the c hange observed during consecutive sea level recordings in 10 control subjec ts. Results - Three climbers experienced slight (grade 1) AMS symptoms both at 4500 m and at maximal altitude exposure (Group 1). Three other climbers (Group 2) had no symptoms at 4500 m, but they developed AMS (grades 1, 2, or 3) at maximal altitude. Alpha amplitudes were higher at 4500 m in group 1 climbers, while it was lower in group 2 climbers compared to the sea leve l recording. Significant time x group interactions in ANOVA were found for delta (P = 0.005), theta (P = 0.001) and alpha (P=0.001) amplitude, indicat ing that QEEG amplitudes decreased significantly at high altitude in group 2 climbers. Conclusion - The QEEG response to moderate hypobaric hypoxia is not uniform, but the direction of QEEG amplitude change, particularly in t he alpha band, may possibly predict the risk of developing AMS.