Poor postural stability in children with vertigo and vergence abnormalities.

PURPOSE An earlier study suggested that deficits of vergence can influence postural control via the efferent and afferent proprioceptive signals. In this study, postural control in 28 children with vertigo with normal vestibular function but with vergence abnormalities and in 19 normal children of comparable age was assessed with orthoptic tests. METHODS A posturography platform was used to examine posture in quiet stance. The child was asked to fixate a target at 40 cm or at 200 cm, either with eyes open (vision condition) or with eyes covered by a black mask (no vision condition). In a complementary test in 15 of 28 children with vertigo and in all 19 normal children, postural control was evaluated during monocular viewing (dominant and nondominant eye viewing). RESULTS For all children examined, postural stability was better when fixating a target at near than at far distance and with both eyes than with one eye or with eyes covered. In all conditions, the children with vertigo were more unstable than were the control children. CONCLUSIONS Binocular visual information, such as vergence disparity, is essential in stabilizing posture at near distance. Postural instability reported in children with vertigo and vergence abnormalities could be due to poor vergence inputs and/or to immature compensatory mechanisms controlling postural stability (vestibular, somatosensory inputs and/or cerebellar processes).