No evidence of intracranial hypertension in trekkers with acute mountain sickness when assessed noninvasively with distortion product otoacoustic emissions.

Aims: The role of intracranial hypertension in acute mountain sickness (AMS) is a matter of debate. Distortion product otoacoustic emissions (DPOAEs) can be used to monitor the intracranial pressure (ICP) noninvasively with a level decrease at the frequencies f(2) = 1 and 1.5 kHz indicating elevated ICP. Methods: DPOAEs (f(2) = 1, 1.5, 2, 3, and 4 kHz), oxygen saturation (Sao(2)) and the Lake Louise score (LLS) to assess AMS were measured in trekking tourists on the Mount Everest trek in Nepal at 2610m and 5170 m. Results: Paired data of both altitudes could be obtained of 187 subjects. All results are given in mean +/- SD. Sao(2) was 94.8 +/- 2.7% at 2610m and 79.0 +/- 6.9% at 5170 m. While at 2610 m, none of the study subjects had AMS (LLS 0.04 +/- 0.02), at 5170m 82 (43.9%) had AMS when defined as LLS > 2, and 31 (16.6%) when defined as LLS > 4 (LLS 2.8 +/- 2.2). DPOAE levels decreased at altitude in all frequencies without a difference between trekkers with AMS and without AMS. Low Sao(2) correlated with high LLS. Low Sao(2) correlated with larger DPOAE level decrease only at f(2) = 1 kHz, while the other frequencies showed no correlation. DPOAE level decrease and LLS showed no correlation. Conclusions: Our data suggest that subjects with AMS symptoms did not have higher ICP compared to healthy subjects. Consequently, it seems unlikely that intracranial hypertension accounts for the symptoms of AMS.