Characteristics of postural stability in patients with aminoglycoside toxicity

Postural stability in patients with bilateral vestibular deficits from aminoglycoside toxicity was characterized by examining their ability to use different sensory cues to maintain balance and by recording their automatic postural responses to sudden translational and rotational (pitch) perturbations of the support surface. We found our patients had increased sway on sensory tests in which either visual or somatosensory cues were altered and were unable to maintain their balance when both visual and somatosensory cues were altered compared to age-matched normal subjects. The amount of vestibular loss, as inferred from the VOR Tc, accounted for a significant amount of A-P sway on test 4 in which somatosensory cues were altered. The frequency response of anterior-posterior sway in the BVL group suggests that they use more hip movements than do normal subjects to maintain postural stability. The responses of BVL patients to sudden translations of the support surface did not differ from those of normal subjects. More BVL patients lost their balance, however, on the initial trial of the toes-up rotational perturbation of the support surface than did normal subjects.