Ge N N, Shea J J, Orchik D J
Baylor College of Medicine, Houston, Texas, USA.
Am J Otol. 1997 Jan;18(1):58-66.
The pathophysiology of hearing deterioration in Ménière's disease (MD) is unclear. Hair cell loss has been proposed to be the cause of severe hearing loss in Ménière's disease. The cochlear microphonic (CM) is known to be the receptor potential of the outer hair cells in the cochlea. This study measured the CM in Ménière's disease and investigated its relationship with the degree of hearing impairment and endolymphatic hydrops. Transtympanic electrocochleography (ECoG) using rarefaction (RAR) and condensation (CON) tonebursts at 1 kHz was performed on 130 ears of 119 patients. Ninety six ears were diagnosed to have MD and 34 were diagnosed non-Ménière's disease (NMD). The mean amplitude of the CM was 33.10 +/- 46.04 microV in the MD group and 13.15 +/- 12.77 microV in the NMD group (p < 0.001). Enlarged negative summating potential and action potential ratios (SP:AP > 40%) were found in 81.3% of the MD group and 17.6% of the NMD group. In the MD group, the CM in the group with an enlarged negative SP was 36.98 +/- 49.78 microV, and 16.31 +/- 15.88 microV in the group without (p < 0.01). The CM was 34.33 +/- 49.28 microV in the pure-tone average (PTA) < or = 25 dB group, 46.97 +/- 58.31 microV in the 26-40 dB group, 29.12 +/- 42.62 microV in the 41-70 dB group, and 26.20 +/- 22.41 microV in the > 70 dB group (p > 0.05). The CMs in 11 pairs of MD ears and sensorineural hearing loss (SNHL) ears with matching hearing (MD 44 dB, SNHL 45 dB) were measured. They were 71.42 +/- 75.94 microV and 7.90 +/- 5.89 microV, respectively (p < 0.01). Our study shows that the CM is higher in ears with endolymphatic hydrops, evidenced by an enlarged SP:AP ratio, than ears without and the CM shows no statistical difference in groups with different levels of hearing loss. These findings suggest that hearing loss with a large CM in Ménière's disease patients may be the result of an alteration of cochlear mechanics and only severe hearing loss with a small CM is caused by hair cell loss. The CM measurement, to evaluate the hair cell status, may be helpful in identifying patients whose hearing may be recoverable if the underlying hydrops can be corrected. Our data do not permit the conclusion that an enlarged CM can be used in the diagnosis of MD.
梅尼埃病（MD）听力减退的病理生理学尚不清楚。有观点认为毛细胞丢失是梅尼埃病严重听力损失的原因。已知耳蜗微音电位（CM）是耳蜗外毛细胞的感受器电位。本研究测量了梅尼埃病患者的CM，并探讨其与听力损害程度和内淋巴积水的关系。对119例患者的130只耳进行了经鼓膜电耳蜗图（ECoG）检查，使用1kHz的疏波（RAR）和密波（CON）短纯音。96只耳被诊断为MD，34只耳被诊断为非梅尼埃病（NMD）。MD组CM的平均幅度为33.10±46.04μV，NMD组为13.15±12.77μV（p<0.001）。MD组81.3%的患者出现负和电位及动作电位比值增大（SP:AP>40%），NMD组为17.6%。在MD组中，负SP增大组的CM为36.98±49.78μV，未增大组为16.31±15.88μV（p<0.01）。纯音平均听阈（PTA）≤25dB组的CM为34.33±49.28μV，26 - 40dB组为46.97±58.31μV，41 - 70dB组为29.12±42.62μV，>70dB组为26.20±22.41μV（p>0.05）。测量了11对听力匹配的MD耳和感音神经性听力损失（SNHL）耳（MD 44dB，SNHL 45dB）的CM。它们分别为71.42±75.94μV和7.90±5.89μV（p<0.01）。我们的研究表明，以内淋巴积水为特征（通过增大的SP:AP比值证明）的耳的CM高于无积水的耳，且CM在不同听力损失水平组中无统计学差异。这些发现表明，梅尼埃病患者中CM较大时的听力损失可能是耳蜗力学改变的结果，只有CM较小时的严重听力损失是由毛细胞丢失引起的。测量CM以评估毛细胞状态，可能有助于识别那些如果潜在积水能够得到纠正听力可能恢复的患者。我们的数据不支持得出增大的CM可用于MD诊断的结论。
