Ectopic Stimulation Factors Limiting Cochlear Implant Outcomes

描述（由申请人提供）：平均而言，不同人工耳蜗（CI）系统的患者语音识别水平非常相似，但使用相同设备的患者观察到很大的结果差异。这些结果表明显著的患者依赖因素影响CI受者的语音识别。我们已经注意到电刺激异位的生理证据，可能产生竞争性的神经活动，并可能与表现下降有关。生理观察是在固定电极刺激的不同记录部位存在系统性的耳蜗内诱发电位潜伏期移位。表现出这种现象的受试者通常报告说，当有人说话时，会出现竞争性的噪音和咕噜声/回声样的声音，这些声音令人讨厌和/或干扰语音识别。潜伏期移位现象最常见于对语音识别能力中等至较差的CI用户的顶触点进行刺激。基于这些和其他结果，我们假设在典型使用CI装置的刺激过程中可能会出现两个空间上独立的激发位点。这个为期两年的探索性项目的主要目标是测试异位兴奋部位假说的具体预测，并评估可能减少异位兴奋发生的替代刺激方法。这些数据将提供有关外周缺损对患者表现影响的新信息，以及可能改善CI受者预后的可选优化参数。这项工作有三个具体目的，包括：(1)验证一个假设，即在尖端耳蜗中有更多电极引起异位兴奋的受试者语音识别得分较低，与设备类型无关；(2)通过检验不同刺激模式对增强和/或减弱异位兴奋的影响，通过检测脑干中继核神经反应的预测潜伏期位移，以及将解剖变异与异位兴奋迹象的发生率联系起来，来检验异位兴奋假说；(3)评价与基于脉冲的语音处理策略相结合时，确定的最小化异位激活的刺激模式是否能提高语音识别。

DESCRIPTION (provided by applicant): On average, patient speech recognition levels across different cochlear implant (CI) systems are highly similar, yet large outcome variation is observed across patients with the same device. These results indicate significant patient-dependent factors influence speech recognition in CI recipients. We have noted physiological evidence of an ectopic site of electrical stimulation that may produce competing neural activity and may be associated with diminished performance. The physiological observation is the presence of systematic latency shifts of intracochlear evoked potentials across different recording sites for stimulation on a fixed electrode. Subjects presenting with this phenomenon often report competing noise and grunt/echo-like sounds which occur when someone is speaking and are annoying and/or disruptive to speech recognition. The latency-shift phenomenon is observed most often with stimulation on apical contacts of CI users with average-to-poor speech recognition. Based on these and other results, we hypothesize that there are two, spatially-separate sites of excitation which may occur during stimulation with a CI device during typical use. The primary goals in this exploratory two-year project are to test specific predictions of the ectopic excitation site hypothesis and to evaluate alternative stimulation methods which may minimize the occurrence of ectopic excitation. These data will provide new information about the effects of peripheral deficits on patient performance and alternative optimization parameters that may improve the outcomes of CI recipients. The work is organized along three specific aims, including (1) to test the hypothesis that subjects with a greater number of electrodes eliciting ectopic excitation in the apical cochlea have lower speech recognition scores, independent of device type; (2) to test the ectopic excitation hypothesis by examining the effects of various stimulus modes on enhancing and/or diminishing ectopic excitation, by testing for predicted latency shifts of neural responses at brainstem relay nuclei, and correlating anatomical variation with the incidence of signs of ectopic excitation; and (3) to evaluate whether stimulation modes identified to minimize ectopic activation improve speech recognition when incorporated into pulsatile-based speech processing strategies. PUBLIC HEALTH RELEVANCE: This project will increase knowledge of patient-specific, physio-anatomical characteristics that may largely determine or limit outcome level in individual cochlear implant patients. This knowledge will lead to patient-specific fitting strategies and custom sound processor designs which best match information coding to the nature of the electrode nerve interface. Specifically, this project will focus on the occurrence of a secondary ectopic site of neural activation that may occur during electrical stimulation with a cochlear implant. The mechanisms of generation and consequences of its occurrence on speech recognition will be explored. Finally, procedures designed to prevent the occurrence of ectopic stimulation will be evaluated.