Vestibular Rehabilitation and Otolith Dysfunction

The primary function of the vestibular (inner ear balance) system is to maintain gaze and postural stability. The vestibular system is comprised of two types of sensory organs (semicircular canals and otolith organs) each with unique contributions to balance. Vestibular Rehabilitation (VR) is the treatment of choice for patients experiencing dizziness, imbalance, and mobility impairments related to vestibular dysfunction. VR typically includes gaze stability exercises, gait and balance training, and general conditioning. Gaze stability exercises were developed based on the concepts of adaptation and substitution with the goal of improving gaze stability by facilitating vestibular compensation of the semicircular canal-mediated vestibulo-ocular reflex (VOR). Many factors that might influence recovery, such as the involvement of different vestibular sensory organs (semicircular canals versus otolith organs) have not been examined to determine their impact on recovery. Most studies examining the effectiveness of VR have used only tests of VOR function (caloric and rotational tests) that measure horizontal semicircular canal to determine vestibular loss. Thus, little is known about interventions to facilitate vestibular compensation of the otolith organs. Recent studies have demonstrated adaptation following otolith organ stimulation using centrifugation (or linear acceleration), but there is no data regarding optimum stimulus parameters. The concept of using centrifugation for otolith adaptation may be similar to using gaze stability exercises for VOR adaptation. Healthy control subjects (n = 5 per experiment) will participate in three separate experiments to determine: (1) the optimum off-axis distance of the rotary chair, (2) the optimum duration of off-axis rotation (OAR), and (3) the optimum OAR stimulation/training schedule.