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 f2=1 and 1.5 kHz indicating elevated ICP.
Methods: DPOAEs (f2=1, 1.5, 2, 3, and 4 kHz), oxygen saturation (Sao2) and the Lake Louise score (LLS) to assess AMS were measured in trekking tourists on the Mount Everest trek in Nepal at 2610 m and 5170 m.
Results: Paired data of both altitudes could be obtained of 187 subjects. All results are given in mean±SD. Sao2 was 94.8±2.7% at 2610 m 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 5170 m 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 Sao2 correlated with high LLS. Low Sao2 correlated with larger DPOAE level decrease only at f2=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.
Keywords: DPOAE; acute mountain sickness; distortion product otoacoustic emissions; high altitude cerebral edema; intracranial pressure; noninvasive assessment.