POSTURAL STABILITY FOLLOWING MILD HEAD OR WHIPLASH INJURIES

Studies of the sequelae of head injury suggest that cochlear and vesti bular dysfunctions comprise some of the most frequently reported delay ed complications following head trauma. To date, little attention has been given to the relation between post-traumatic subjective symptoms of dizziness and the objective measures of postural stability or balan ce. The purpose of this study was to quantify the balance deficits in individuals who had developed symptoms of dizziness following mild hea d and whiplash injuries. The balance abilities of 29 patients, who dev eloped dizziness following some type of mild head or whiplash injury, were compared to those of 51 healthy symptom-free subjects. Balance wa s assessed by examining the center-of-pressure movements, in the anter ior-posterior and medial-lateral directions, and the total movement di splacement. The isolated contributions of visual and somatosensory inp uts were estimated by comparing the magnitudes of the center-of-pressu re movements for the various sensory conditions. Data were collected f rom three 30-second trials of each combination of three visual conditi ons (accurate, absent, and inaccurate) and two somatosensory condition s (accurate and inaccurate), with the patient standing on a fixed-forc e platform. Univariate analyses of variance indicated that the group w ith head injury, compared to the control group, exhibited significantl y greater anterior-posterior movements in four of the six sensory cond itions and greater total movement displacement during the inaccurate v ision/inaccurate somatosensation condition. These data suggest that pa tients who have sustained head or neck trauma exhibit increased relian ce on accurate visual input and are unable to utilize internal vestibu lar orienting information to resolve conflicting information from the visual and somatosensory systems.