Aim: 

The exposure to high altitude hypobaric hypoxic environment results in a lot of organic responses and adaptation mechanisms. Depending on the absolute altitude and the duration of exposure, some effects, named mountain sickness, are evident, including cardiovascular and pulmonary responses and cerebral dysfunctions (Hainsworth et al, Clin Auton Res. 17:13, 2007; Wilson et al, Lancet Neurol. 8:175, 2009).

Methods: 

In this study we analysed the vestibular reactivity and the postural stability of seven climbers before and after a 21-day period of exposition to hypobaric hypoxia (over 5000 m). To obtain this goal we tested: 1- the vestibular nerve activity using the Vestibular Evoked Myogenic Potentials (VEMPs) and the bithermal caloric test, and 2- the postural stability by static stabilometry. Results: Our data revealed that all subjects improved their stability with significant reduction of the statokinesigram and support surface. Only four subjects improved the Romberg index. The vestibular tests revealed normal values. After the hypobaric hypoxia exposition, the caloric test was reduced in three subjects; among which, two showed reduced VEMPs and one improved VEMPs. The same two patients with vestibular imbalance, reported a transitory positional vertigo at 12 and 13 day of exposition.

Conclusion: 

In conclusion this experience suggests that the high altitude can modify the vestibular function and improve the stability primarily by the visual stimulus and subsequently by physical efforts.