An Intracochlear Approach to Improving the Clinical DP-Gram

 描述（由申请人提供）： 畸变产物耳声发射（DPOAE）作为一种提供耳蜗状态的非侵入性窗口的手段，既可以促进我们对耳蜗功能的科学知识，又可以为临床设备提供快速的听力损伤测试，具有很大的前景。然而，当在退伍军人等感音神经性听力损失患者中以约f1=65和f2=55 dB SPL的推荐主音调水平进行测量时，较差的信噪比（SNR）通常使临床解释变得困难。由较高的初级水平引起的DPOAE具有更好的SNR，但由于兴奋和DPOAE分量的相关基础扩散，灵敏度和频率特异性都较低。如果能克服这些缺点，DPOAE在临床上的适用性将大大提高。拟议的研究计划的主要意义是进一步了解耳道DPOAE与颅内DPs（iDPs）的关系，以改善在中至高纯音水平下测量的DP图，用于临床目的：1）了解耳道DPOAE频率特异性明显增加的基础，- 通过同时测量DPOAE和直接观察IT对沙土鼠模型中基底膜（BM）附近的f2和iDP的影响的oct IT程序; 2）将这些颅内测量结果与使用非侵入性iDP技术获得的测量结果进行比较，其中f3音与iDP配对以产生用于推断iDP行为的DPOAE。该比较将确立非侵入性耳道方法用于检查iDP行为的有效性，并确定DPOAE和iDP之间的差异; 3）使用BM附近的直接颅内压测量同时测量耳道DPOAE和iDP的响应/生长或输入/输出功能。通过这种方法，可以开发DPOAE的传递函数，预测耳蜗内iDP的行为。计划中的研究还将比较标准DP-gram程序与两种新程序（<$-oct IT DP- gram和iDP-gram）在4- 6 kHz范围内噪声诱导听力计切迹的退伍军人人群中的性能。总的来说，所提出的实验的前提是，通过确定传统的耳道DPOAE和耳蜗内产生的iDP之间的差异，将提供一种提高用中到高水平的初级音调获得的临床DP图测试的频率特异性的方法。完成更具有频率特异性的DP图将使临床医生能够使用高水平的主要音调可靠地建立外毛细胞损伤的模式，以在患有感音神经性听力损失的退伍军人中获得足够的SNR。

 DESCRIPTION (provided by applicant): PROJECT SUMMARY/ABSTRACT Distortion product otoacoustic emissions (DPOAEs) hold great promise as a means of providing a noninvasive window into the status of the cochlea that can both advance our scientific knowledge about cochlear function, and contribute a rapid test of hearing impairment to the clinical armamentarium. However, when measured at recommended primary-tone levels of about f1=65 and f2=55 dB SPL in patients with sensorineural hearing loss such as Veterans, poor signal-to-noise ratios (SNRs) often make clinical interpretations difficult. DPOAEs elicited by higher primary levels have better SNRs, but are both less sensitive and less frequency specific due to the associated basal spread of both excitation and DPOAE components. If these shortcomings could be overcome, the applicability of DPOAEs in the clinic would be greatly enhanced. The primary significance of the proposed program of research is to further our knowledge of ear-canal DPOAEs vs intracochlear DPs (iDPs) to improve DP-grams measured at moderate to high primary-tone levels for clinical purposes by: 1) understanding the basis of the apparent increase in frequency specificity of the ¿-oct IT procedure by simultaneous measures of both the DPOAE and direct observations of the effects of the IT on f2 and iDP near the basilar membrane (BM) in a gerbil model; 2) comparing these intracochlear measures to those obtained with a noninvasive iDP technique where an f3 tone is paired with the iDP to produce a DPOAE´ used to infer the behavior of the iDP. This comparison will establish the validity of the noninvasive ear-canal method for examining the behavior of iDPs, and determine the differences between DPOAEs and iDPs; and 3) simultaneously measuring the response/growth or input/output functions for both the ear-canal DPOAE´ and the iDP using direct intracochlear pressure measures near the BM. With this approach, transfer functions for the DPOAE´ can be developed that predict the behavior of the iDP inside the cochlea. The planned studies will also compare the performance of the standard DP-gram procedure to two new procedures, the ¿-oct IT DP- gram and the iDP-gram in a population of Veterans with noise-induced audiometric notches in the 4- to 6-kHz range. On the whole, the premise of the proposed experiments is that by determining the differences between conventional ear-canal DPOAEs and iDPs generated within the cochlea, a means towards improving the frequency specificity of clinical DP-gram tests obtained with moderate- to high-level primary tones will be provided. Accomplishing a more frequency-specific DP-gram will allow clinicians to reliably establish the pattern of outer hair cell damage using high-level primary tones to achieve adequate SNRs in Veterans with sensorineural hearing loss.