Balance Prostheses for Postural Control Preventing Falls in the Balance Impaired By Displaying Body-Tilt Information to the Subject via an Array of Tactile Vibrators

here is a clear need for a prosthesis that improves pos-tural stability in the balance impaired. Such a device would be used as a temporary aid during recovery from ablative inner-ear surgery and as a permanent prosthe-sis for those elderly prone to falls. In the article we discuss a single-axis research device we have developed to provide balance impaired subjects with a noninvasive, vibrotactile display of body tilt, which helps them reduce their body sway during standardized tests. For those with normal balance function, the inner ear's vestib-ular system provides self-motion cues that help stabilize our vision while moving, that enable us to orient ourselves with respect to our surroundings, and that help us stand and walk. Each inner ear can sense, in three dimensions (3-D), angular motion and linear acceleration summed with gravity [41]. The central nervous system (CNS) can process these cues to estimate self motion in six degrees of freedom (dof), three angular and three linear. When either the inner ear, the 8th nerve that connects it to the CNS, or the CNS portion that processes self-motion information malfunctions due to injury, disease, or to prolonged exposure to altered gravity (such as a deep space voyage), this useful information is lost or distorted. This loss of information can force subjects to rely on other cues from vision or proprioception, which may not always be accurate. This reduction of motion cues produces dizziness, blurred vision, inability to orient correctly, and reduced ability to stand or walk. A serious consequence is an increase in the risk of falling in the elderly. Over 90 million Americans (more than 40% of the population) will seek medical attention for dizziness at least once in their lifetime. At least 2 million Americans suffer or experience chronic impairment due to dizziness or balance disorders , resulting in annual medical costs exceeding US$1 billion [26]. Depending on the disease, not all patients respond well to existing treatments. As discussed below, many could benefit from a vestibular prosthesis. Biomedical research is presently being conducted on both implantable and nonimplantable balance prostheses. Currently , no patients have had vestibular implants, and only limited laboratory-based experiments have been done using nonimplantable devices. Building upon Suzuki and Cohen [10], [9], [31], [32], Merfeld recently demonstrated responses in monkeys that are first steps toward an implantable prosthe-sis [19], [23]. An implantable prosthesis offers attractive features including: portability, intuitive operation, replacement …