The neural basis of clinical vestibular testing by bone conducted sound

内耳平衡系统(前庭系统)的功能障碍会导致反复发作的眩晕和持续性的不稳定，这可能会扰乱一些人一生中最有生产力的岁月。与平衡有关的跌倒占老年人意外死亡的一半以上(Marchetti和Whitney 2005)。尽管如此，大多数医生发现头晕很难诊断，几乎不可能治疗，部分原因是患者报告的主观性。需要快速、简单、安全、客观的临床测试来诊断这些患者的问题，并确定10个前庭感觉区域中的哪个受到影响。一种测试平衡功能的新方法是使用声音，因为声音既可以激活前庭系统，也可以激活听觉系统。我们正在利用这一事实来开发一种全新的前庭功能临床测试方法，这种在很大程度上是澳大利亚的开发已经迅速被国际前庭社区接受。在最近的NHMRC项目(253620)中，我们发现1)骨传导振动特异性地激活平衡系统(耳石)的重力传感区域之一的某些感觉神经，2)空气传导(AC)声和骨传导振动(BCV)似乎探测不同前庭感觉区域的功能3)最重要的是，BCV在清醒的豚鼠中引起眼动反应(就像它在清醒的人类受试者中所做的那样)。这似乎是我们正在寻求的耳石功能测试的客观反应。在这个项目中，我们计划通过记录豚鼠单个前庭神经细胞来扩展这些结果，测试关于它们对各种声音的反应的假设，然后向神经元注入染色，这将使我们能够明确地确认声音刺激激活的受体的位置。这一结果将成为使用骨传导振动进行新的临床平衡测试的生理学基础。

Dysfunction of the balance system of the inner ear (the vestibular system) causes recurring dizzy attacks and persistent unsteadiness which can disrupt the most productive years of some people's lives. Balance-related falls account for more than half of accidental deaths in the elderly (Marchetti and Whitney 2005). Despite this, most doctors find dizziness difficult to diagnose and almost impossible to treat in part because of the subjective nature of the patients' reports. Fast, simple, safe, objective clinical tests are needed to diagnose these patients' problems and to identify which of the 10 vestibular sensory regions is affected. A new way of testing balance function is to use sound because sound can activate the vestibular system as well as the auditory system. We are using that fact to develop a whole new way of clinical testing of vestibular function and this largely Australian development has been very rapidly accepted by the international vestibular community. In a recent NHMRC project (253620) we discovered 1) that bone conducted vibration specifically activates some sensory nerves from one of the gravity sensing regions of the balance system (the otoliths) and 2) that air-conducted (AC) sound and bone-conducted vibration (BCV) appear to probe the function of different vestibular sensory regions 3) most importantly that BCV causes an eye movement response in alert guinea pigs (as it does in alert human subjects). This seems to be the objective response for testing otolith function which we are seeking. In this project we plan to extend these results by recording single vestibular nerve cells in guinea pigs, testing hypotheses about their responses to various types of sound and then injecting the neurons with stains which will allow us to confirm definitely the location of the receptors activated by the sound stimuli. The outcome will be the physiological basis of a new clinical test of balance using bone conducted vibration.