Article révisé par les pairs
Résumé : Postural control can vary in accordance with many physical and psychological variables. To reduce the resulting intra-individual disparity of postural responses, we have studied their evolution when repeating an unbalancing stimulation three times with eyes opened and then closed. A 6°toe-up tilt of the support surface induces a backward fall of the body which is recorded by a multisegmental posturography with electromagnetic sensors (Statitest-Mumedia). The backward fall is normally prevented by a postural response which is quantified by its forward acceleration vector. This acceleration initially occurs 200 ms after the tilt of the support surface. There is a 50-ms increase in the mean latencies between the responses of the first and the sixth stimulation while the acceleration amplitude decreases by 25%. A progression index quantifies this evolution to a better management of the postural response. Eye closing temporarily stops this progression. Despite a significant increase in the first latencies, this progression also occurs in two patients representing typical balance disorders of cerebellar or parkinsonian origin. On the contrary, the progressive increase of the acceleration amplitude clearly discriminates a patient suffering from phobic vertigo. Copyright (C) 2000 S. Karger AG, Basel.