耳蜗突触病变与频段精细定位隐性听力损失的时域、频域及响度研究

Most people with aging, noise or ototoxic drugs explored history complain about hidden hearing loss. Recent research shows that cochlear synaptopathy probably leads to hidden hearing loss. Psychoacoustics researches showed that there were abnormal temporal, frequency and loudness perception in the frequency where the threshold was within normal in steep high-frequency hearing loss individuals. Our previous study displayed that individuals with only high-frequency (≥8 kHz) hearing loss exerted frequency range limited hidden hearing loss in the low frequency which just beneath the hearing loss high-frequency. We hypothesize that the frequency distribution of cochlear synaptopathy give rise to the frequency range limited hidden hearing loss. In this study, we apply different frequencies low-pass filtered distortion speech and temporal, frequency and loudness evaluation measures, to estimate the frequency range with hidden hearing loss. To locate the frequency range with cochlear synaptopathy, we also adopt objective indicators of electrophysiology, such as frequency specific ECochG SP/AP and ABR wave Ⅰ potential. We apply correlation analysis and regression analysis using the indicators of electrophysiology and speech discrimination indexes according to frequency, to elucidate the mechanism of cochlear synaptopathy caused frequency range limited hidden hearing loss, and to offer a new idea for clinical frequency precision intervention and rehabilitation with hidden hearing loss related diseases such as presbycusis, noise-induced hearing loss and ototoxic drug-induced hearing loss.

隐性听力损失广泛存在于老年人及噪声、耳毒性药物接触人群中。现有研究表明耳蜗突触病变很可能是隐性听力损失的病理基础。心理声学研究发现，纯音听阈测试表现为陡降型听力下降患者，听阈正常频段内存在时域、频域及响度感知障碍。我们研究发现，纯音听阈测试8kHz以上听力受损患者，8kHz下游紧邻的频段内存在言语感知障碍。我们认为频段特异性的耳蜗突触病变导致相应频段的隐性听力损失。本研究通过检测不同频段言语识别阈及时域、频域和响度感知的差别阈，探索隐性听力损失存在的频段及特征；采用频率特异性的耳蜗电图SP/AP和听觉脑干反应Ⅰ波幅值，作为评估不同频段耳蜗突触病变的客观电生理指标，对耳蜗突触病变进行精细定位。分频段对电生理指标和心理声学指标进行相关及回归分析，阐明耳蜗突触病变导致频段特异性隐性听力损失的机制，为隐性听力损失相关的老年性聋、噪声性聋及耳毒性药物聋等疾病的临床频段精准干预及康复提供新思路。

隐性听力损失存在于老年、噪声和耳毒性药物接触人群中，既往研究表明耳蜗突触病变很可能是隐性听力损失的病理基础。隐性听力损失临床尚无可靠诊断依据，为得到可靠的隐性听力损失病例，本课题组依据严格的年龄界限、噪声暴露年限、听力检测结果，从3000名职业噪声暴露工人中筛选听阈正常的被试纳入隐性听力损失高危组，筛选年龄匹配、未接受职业噪声暴露、听阈正常的受试纳入对照组。考察高危组与对照组不同频段噪声下言语识别率、时间间隔阈值、响度感知差别阈及耳蜗电图SP/AP，并将噪声下言语识别率分别与耳蜗电图SP/AP及时间间隔阈值进行相关分析。结果表明：①与对照组相比，高危组噪声下完整言语及4,2,1kHz低通过滤言语的识别能力下降，4,2,1kHz信号的时间分辨能力和响度感知能力下降；②高危组耳蜗电图SP/AP比值升高；③畸变言语识别率、时间间隔阈值与短声刺激诱发的双耳耳蜗电图SP/AP均值的相关分析结果提示，耳蜗电图SP/AP均值与噪声下完整语音识别率和2kHz低通过滤语音识别率呈显著负相关；耳蜗电图SP/AP均值与4,2,1 kHz时间间隔阈值的相关性不显著。畸变言语识别率与时间间隔阈值的相关性研究显示，仅4kHz低通过滤言语识别率与4kHz时间间隔阈值呈显著负相关。综上，隐性听力损失患者存在频率节段性的言语功能及时程、响度处理能力下降；噪声下低通过滤的言语识别能力与突触病变存在一定相关性，噪声下低通过滤的言语识别能力与分频时程处理能力也存在一定相关性。我们认为下降的噪声下言语识别能力仅用突触病变并不能完全解释。这些结果提示隐性听力损失人群存在频率节段性的言语识别及时程处理能力下降，其病理机制复杂，耳蜗突触病变是其中之一。在制定助听器压缩策略及人工耳蜗编码策略时，不仅需要关注听阈受损频率的信号调制，也需要对听阈正常频率的信号进行适当调制，以获得更好的噪声下言语识别率。