Visual dependence and spatial orientation in benign paroxysmal positional vertigo.

People with benign paroxysmal positional vertigo (BPPV) probably have otoconial particles displaced from the utricle into the posterior semicircular canal. This unilateral change in the inertial load distributions of the labyrinth may result in visual dependence and may affect balance control. The goal of this study was to explore the interaction between visual dependence and balance control. We compared 23 healthy controls to 17 people with unilateral BPPV on the Clinical Test of Sensory Interaction and Balance on compliant foam with feet together, the Rod-and-Frame Test and a Mental Rotation Test. In controls, but not BPPV subjects, subjects with poor balance scores had significantly greater visual dependence, indicating that reliance on visual cues can affect balance control. BPPV and control subjects did not differ on the mental rotation task overall but BPPV reaction time was greater at greater orietantions, suggesting that this cognitive function was affected by BPPV. The side of impairment was strongly related to the side of perceived bias in the Earth vertical determined by BPPV subjects, indicating the relationship between the effect of asymmetric otolith unloading with simultaneous canal loading on spatial orientation perception.