Structure and Function Relations in Middle Ears

描述（申请人提供）：中耳对听觉功能至关重要。中耳疾病是导致听力损失的最常见原因，目前已开发出多种治疗方法。耳外科医生通常修复或重建中耳部分或整个。然而，这些重建的成功是有限的，特别是在更严重的中耳疾病后。结构-功能关系的知识对改进重建技术至关重要。我们已经开发了基于生理学的模型来解决以下问题：正常耳，例如鼓膜松弛部（TM）的功能；病理耳，如TM穿孔；和重建，如镫骨切除术和IV型鼓室成形术。我们建议接下来关注四个重要的结构-功能问题：(1)一种新描述的临床实体，上半圆形管开裂综合征，与对空气传导和骨传导声音的敏感性改变以及由响亮的声音或耳道静压引起的眩晕有关。我们在动物模型中寻找导致听力变化的机制，在动物模型中我们产生不同大小和位置的管道开裂。结果可以定义一个听力测试，表明裂孔的大小和位置。(2)中耳静压引起的听力敏感性丧失是常见的。听力损失被认为是由中耳门韧带和中耳韧带的非线性弹性特性造成的，但这些结构的相对重要性尚不清楚。其特点是：(a)正负压的影响在性质上不同，(b)对导纳的影响在量级上不同于对传输的影响。这个项目将确定这些特征的原因和产生它们的结构。(3)高频中耳响应通常被认为受惯性力的限制，但测量结果并不支持这一假设。我们建议在沙鼠和猫科的几个物种中进行测量，其中不同大小的物种（小型猫到老虎）在中耳结构的大小上有自然的变化。结果应确定高频中耳功能的重要机制。(4)最近的研究表明，在颞叶环上存在一种新的平滑肌元件。我们将量化这块肌肉对中耳声学特性的影响，并评估其作为中枢神经系统控制中耳传播的潜力。

DESCRIPTION (provided by applicant): The middle ear is vital to auditory function. Middle-ear disease is the most common cause of hearing loss, and a wide range of treatments have been developed. Ear surgeons routinely repair or reconstruct middle-ear parts or the whole. However, the success of these reconstructions is limited, especially after more severe middle-ear disease. Knowledge of structure-function relations is crucial to improvements in reconstructive techniques. We have developed physiologically-based models that address issues relating to: normal ears, e.g. the function of the pars flaccida of the tympanic membrane (TM); pathological ears, e.g. perforations of TM; and reconstructions, e.g. stapedectomy and type IV tympanoplasty. We propose next to focus on four important structure-function issues: (1) A newly described clinical entity, superior-semicircular-canal dehiscence syndrome, is associated with altered sensitivity for air-conducted and bone-conducted sound, and vertigo precipitated by loud sounds or static pressure in the ear canal. We seek the mechanisms responsible for the hearing changes in an animal model where we produce canal dehiscences of varied size and location. Results could define a hearing test that indicates size and location of the dehiscence. (2) Loss of hearing sensitivity caused by static pressure in the middle ear is common. The loss in hearing is assumed to result from the nonlinear elastic properties of the TM and middle-ear ligaments, but the relative importance of these structures is unknown. Features are: (a) Positive and negative pressures have qualitatively different effects, and (b) Effects on admittance differ in magnitude from those on transmission. This project will determine reasons for these features and the structures that produce them. (3) Middle-ear response at high frequencies is often assumed to be limited by inertial forces, but measurements do not support this assumption. We propose measurements in gerbil and in several species of the cat family, where species of different size (small cats to tiger) provide natural variations in the size of middle-ear structures. Results should define important mechanisms involved in high-frequency middle-ear function. (4) Recent work has demonstrated a novel smooth-muscle element at the annulus of the TM. We will quantify this muscle's effect on the acoustic properties of the middle ear and assess its potential as a site for CNS control of middle-ear transmission.