Postural ataxia at high altitude is not related to mild to moderate acute mountain sickness

Abstract.

To evaluate the role of acute mountain sickness (AMS) in the pathogenesis of stance abnormalities occurring at high altitude, static posturography was applied to 22 healthy subjects at an altitude of 450 m and during a 3-day sojourn at 4559 m. Subjects stood on a platform and sway velocity (S), and sway velocity in the antero-posterior (S_AP) and medio-lateral (S_ML) directions was recorded for 20 s with eyes open (EO) and 20 s with eyes closed (EC). Arterialized blood from an ear lobe was analyzed to determine the arterial partial pressures of oxygen (P _aO₂) and carbon dioxide, and oxygen saturation (S _aO₂). AMS was assessed by the environmental symptom questionnaire (ESQ) of Sampson (cerebral AMS, AMS-C score >0.7). AMS affected four subjects on day 1, ten subjects on day 2, and five subjects on day 3. Posturographic findings showed no difference between subjects with AMS and healthy subjects, and no correlation with the ESQ score. P _aO₂ and S _aO₂ showed non-significant trends toward lower values in subjects with AMS than in those without AMS. Posturographic parameters significantly worsened on the 1st (EO-S, P<0.001; EC-S, P<0.01; EO-S_ML, P<0.05), 2nd (EO-S, EC-S and EO-S_ML, P<0.01) and 3rd days (EC-S, P<0.05) at high compared to low altitude. Differences in AMS-C score, S _aO₂ and P _aO₂ were significant between low and high altitude (P<0.0001). Our data suggest that AMS is not important in the pathogenesis of postural ataxia occurring at high altitude.