Middle Ear Muscle Reflex and Word Recognition in "Normal-Hearing" Adults: Evidence for Cochlear Synaptopathy?
Middle Ear Muscle Reflex and Word Recognition in "Normal-Hearing" Adults: Evidence for Cochlear Synaptopathy?
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DOI：
10.1097/aud.0000000000000804
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发表时间：
2020-01-01
期刊：
影响因子：
3.7
通讯作者：
Maison, Stephane F.
中科院分区：
文献类型：
--
作者：
Mepani, Anita M.;Kirk, Sarah A.;Maison, Stephane F.
目的：噪声暴露、耳毒性药物或衰老后的永久性阈值升高是由感觉细胞的丧失引起的;然而，动物研究表明，毛细胞的丧失通常是在感觉细胞和听觉神经纤维之间的突触变性之前。这些神经元的沉默，特别是那些具有高阈值和低自发率的神经元，降低了听觉处理，并可能导致在噪声中理解语音的困难。虽然可以通过测量阈上听觉脑干反应来诊断动物的耳蜗突触病，但其在人类中的诊断仍然是一个挑战。在小鼠中，耳蜗突触病也与中耳肌（MEM）反射强度的测量相关，可能是因为缺失的高阈值神经元是这种反射的重要驱动因素。作者假设，MEM反射的措施可能是更好的比其他检测外周功能在困难的听力环境中预测困难的听力在人类subjects.Design：作者招募了165名听力正常的健康受试者，年龄在18岁至63岁之间，没有历史的耳朵或听力问题，没有神经系统疾病的历史，和不显着的耳镜检查。在安静和困难的听力情况下的单词识别是通过四种方式测量的：使用西北大学听觉测试6号语料库中的孤立单词，（a）0 dB信噪比，（B）45%时间压缩混响，或（c）65%时间压缩混响，和（d）修改版本的QuickSIN。在标准和扩展高频下评估听力阈值。畸变产物耳声发射（DPOAEs）评估外毛细胞功能。使用三种方法评估中耳功能和反射：临床测量的声反射阈值，临床测量的宽带鼓室导抗，以及使用同侧噪声激发器两侧的一对点击探针的定制宽带方法。外周听觉功能的其他方面进行了评估，通过测量点击诱发的总电位，即，求和电位（SP）和动作电位（AP）从耳道electrosts.Results：调整年龄和性别后，单词识别分数与听力或DPOAE阈值，在标准或扩展的高频率不相关。MEM反射阈值与孤立词识别分数显著相关，但与QuickSIN的修改版本无关。使用定制测定观察到最高的成对相关性。AP测量值与一些单词评分相关，但不像MEM定制测定中观察到的那么高，并且仅当从SP峰到AP峰而不是基线到AP峰测量振幅时。在所有四项测试中，SP/AP比率与单词分数的配对相关性最高，其次是SP本身。当所有的预测变量结合在逐步多元回归，SP/AP占主导地位的模型，所有四个字的得分结果。MEM测量仅增强了45%时间压缩测试的调整后r（2）值。唯一的其他预测因素，增强模型的性能（只有两个结果的措施）是措施的interaural阈值asymmetrical.Conclusions：结果表明，听力正常的科目，有一个显着的周边贡献减少听力表现在困难的听力环境中，没有捕获的阈值测听或DPOAE。单词分数与SP/AP、SP、MEM反射阈值或AP振幅（按此顺序）之间的显著单变量相关性与一种类型的原发性神经变性一致。然而，解释是模糊的不确定性的混合前和突触后的贡献点击诱发的SP。这里提出的分析没有一个敏感性诊断神经退行性疾病的个案的基础上，然而，这些测试可能是有用的纵向研究，以跟踪积累的神经退行性疾病在个别科目。
Objectives: Permanent threshold elevation after noise exposure, ototoxic drugs, or aging is caused by loss of sensory cells; however, animal studies show that hair cell loss is often preceded by degeneration of synapses between sensory cells and auditory nerve fibers. The silencing of these neurons, especially those with high thresholds and low spontaneous rates, degrades auditory processing and may contribute to difficulties in understanding speech in noise. Although cochlear synaptopathy can be diagnosed in animals by measuring suprathreshold auditory brainstem responses, its diagnosis in humans remains a challenge. In mice, cochlear synaptopathy is also correlated with measures of middle ear muscle (MEM) reflex strength, possibly because the missing high-threshold neurons are important drivers of this reflex. The authors hypothesized that measures of the MEM reflex might be better than other assays of peripheral function in predicting difficulties hearing in difficult listening environments in human subjects.Design: The authors recruited 165 normal-hearing healthy subjects, between 18 and 63 years of age, with no history of ear or hearing problems, no history of neurologic disorders, and unremarkable otoscopic examinations. Word recognition in quiet and in difficult listening situations was measured in four ways: using isolated words from the Northwestern University auditory test number six corpus with either (a) 0 dB signal to noise, (b) 45% time compression with reverberation, or (c) 65% time compression with reverberation, and (d) with a modified version of the QuickSIN. Audiometric thresholds were assessed at standard and extended high frequencies. Outer hair cell function was assessed by distortion product otoacoustic emissions (DPOAEs). Middle ear function and reflexes were assessed using three methods: the acoustic reflex threshold as measured clinically, wideband tympanometry as measured clinically, and a custom wideband method that uses a pair of click probes flanking an ipsilateral noise elicitor. Other aspects of peripheral auditory function were assessed by measuring click-evoked gross potentials, that is, summating potential (SP) and action potential (AP) from ear canal electrodes.Results: After adjusting for age and sex, word recognition scores were uncorrelated with audiometric or DPOAE thresholds, at either standard or extended high frequencies. MEM reflex thresholds were significantly correlated with scores on isolated word recognition, but not with the modified version of the QuickSIN. The highest pairwise correlations were seen using the custom assay. AP measures were correlated with some of the word scores, but not as highly as seen for the MEM custom assay, and only if amplitude was measured from SP peak to AP peak, rather than baseline to AP peak. The highest pairwise correlations with word scores, on all four tests, were seen with the SP/AP ratio, followed closely by SP itself. When all predictor variables were combined in a stepwise multivariate regression, SP/AP dominated models for all four word score outcomes. MEM measures only enhanced the adjusted r(2) values for the 45% time compression test. The only other predictors that enhanced model performance (and only for two outcome measures) were measures of interaural threshold asymmetry.Conclusions: Results suggest that, among normal-hearing subjects, there is a significant peripheral contribution to diminished hearing performance in difficult listening environments that is not captured by either threshold audiometry or DPOAEs. The significant univariate correlations between word scores and either SP/AP, SP, MEM reflex thresholds, or AP amplitudes (in that order) are consistent with a type of primary neural degeneration. However, interpretation is clouded by uncertainty as to the mix of pre- and postsynaptic contributions to the click-evoked SP. None of the assays presented here has the sensitivity to diagnose neural degeneration on a case-by-case basis; however, these tests may be useful in longitudinal studies to track accumulation of neural degeneration in individual subjects.