Avan P, Bonfils P, Loth D, Elbez M, Erminy M
Biophysics Laboratory, Faculty of Medicine, University of Auvergne, Clermont-Ferrand, France.
J Acoust Soc Am. 1995 May;97(5 Pt 1):3012-20. doi: 10.1121/1.411866.
Transient-evoked otoacoustic emissions (TEOE) disappear when hearing loss exceeds 40 dB in the range 1-4 kHz, due to impairment of cochlear outer hair cells. Early screening of sensorineural hearing losses is based on this finding. However, little is known as to the frequency specificity of TEOE abnormalities in a damaged cochlea. TEOE were recorded in 18 normally hearing guinea pigs in a range from 1.5 to 5 kHz before and after exposure to loud pure tones (3-10 kHz, 95-105 dB SPL, 1-10 min). The thresholds of eighth-nerve compound action potentials (CAP) were monitored with a round-window electrode; it was confirmed that acoustic overexposure resulted in typical high-frequency threshold elevations (10 to 50 dB). Most TEOE components were found at lower frequencies at which CAP thresholds did not change. However, a significant linear regression was found between their amplitudes and the percentage of basal cochlea with unaltered CAP thresholds (r = 0.69, p < 0.0001). Two alternative hypotheses are proposed to account for this correlation. Either acoustic trauma induced some minute cochlear damage at places tuned to low frequencies and TEOE were more sensitive to it than CAP thresholds, or significant contributions to lower-frequency TEOE came from the most damaged cochlear places tuned to much higher frequencies.
由于耳蜗外毛细胞受损，当1 - 4 kHz范围内听力损失超过40 dB时，瞬态诱发耳声发射（TEOE）消失。感音神经性听力损失的早期筛查正是基于这一发现。然而，对于受损耳蜗中TEOE异常的频率特异性却知之甚少。在18只听力正常的豚鼠暴露于高声强纯音（3 - 10 kHz，95 - 105 dB SPL，1 - 10分钟）前后，记录了1.5至5 kHz范围内的TEOE。用圆窗电极监测第八神经复合动作电位（CAP）的阈值；证实了声过度暴露导致典型的高频阈值升高（10至50 dB）。大多数TEOE成分出现在CAP阈值未改变的较低频率处。然而，发现它们的振幅与耳蜗基底部分CAP阈值未改变的百分比之间存在显著的线性回归（r = 0.69，p < 0.0001）。提出了两种替代假说来解释这种相关性。要么是声创伤在调谐到低频的部位诱发了一些微小的耳蜗损伤，而TEOE对此比CAP阈值更敏感，要么是对低频TEOE的显著贡献来自于调谐到高得多频率的受损最严重的耳蜗部位。
