Motion sickness and equilibrium ataxia.

In order to know the relationship between motion sickness and equilibrium ataxia, we performed Graybiel's ataxia test battery on 10 normal subjects: 1) before donning goggles which reversed the optical image horizontally and vertically; 2) while wearing the goggles and walking; and 3) after walking as long as possible up to 90 min. Horizontal reversal of vision resulted in a statistically significant decrease in the score for all the closed-eyes tests and one open-eyes test performed during walking and after walking, respectively. In contrast, walking while wearing vertical reversing goggles produced a significant but very small change for one of the closed-eyes tests alone. The present study indicates that failure to detect spatial orientation, which evokes autonomic nervous symptoms as an alarm sign, produces equilibrium ataxia by impairing the top-down regulation of body balance, and that vertically reversed vision does not impair spatial orientation needed to maintain upright posture or to execute locomotion.