Introduction: The Carhart notch is a well-known sign of stapes fixation. However, previous studies have reported that the Carhart notch is not specific to stapes fixation and is also present in other middle ear diseases. Therefore, this study investigated the diagnostic value of threshold gap between air conduction and bone conduction (ABG) for stapes fixation, instead of the bone conduction dip representing the Carhart notch. Methods: A total of 199 ears that underwent exploratory tympanotomy were enrolled in this retrospective study. They were categorized into three groups according to surgical findings: stapes fixation (SF), other ossicle fixation (OF), and chain disconnection (CD). Preoperative pure-tone audiograms and impedance audiograms were compared between the groups. Results: The incidence of the Carhart notch did not differ between the groups. The ABG at 2,000 Hz showed a good diagnostic performance for distinguishing between the SF and CD groups (area under the curve, AUC = 0.816, p #x3c; 0.001), but poor performance for distinguishing between the SF and OF groups (AUC = 0.662, p = 0.003). Bone conduction at 2,000 Hz showed a moderate performance for distinguishing between the SF and CD groups (AUC = 0.707, p #x3c; 0.001) and did not show statistically significant results for distinguishing between the SF and OF groups (AUC = 0.594, p = 0.080). The tympanic membrane compliance was significantly higher in the CD group than in the SF group (p = 0.001). Conclusions: The Carhart notch was not a specific finding of SF. The sensitivity and specificity of ABG ≤15 dB at 2,000 Hz for distinguishing between SF and CD were 60.4% and 89.2%, respectively. To prepare for surgical interventions in patients with conductive hearing loss but a normal tympanic membrane, clinicians should comprehensively consider these results.
Audiol Neurotol

中文翻译：

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镫骨固定气骨阈值间隙的诊断价值

简介： Carhart 切迹是众所周知的镫骨固定标志。然而，之前的研究报告称，Carhart 切迹并非镫骨固定所特有，也存在于其他中耳疾病中。因此，本研究调查了气导和骨导 (ABG) 之间的阈值间隙对镫骨固定的诊断价值，而不是代表 Carhart 切迹的骨导倾角。方法：共有 199 只接受过鼓室探查术的耳被纳入这项回顾性研究。根据手术结果将他们分为三组：镫骨固定 (SF)、其他听小骨固定 (OF) 和链断开 (CD)。比较各组术前纯音听力图和阻抗听力图。结果： Carhart 切迹的发生率在各组之间没有差异。2,000 Hz 的 ABG 在区分 SF 和 CD 组方面表现出良好的诊断性能（曲线下面积，AUC = 0.816， p #x3c；0.001），但在区分 SF 和 OF 组方面表现不佳（AUC = 0.662 , p = 0.003)。2,000 Hz 的骨传导在区分 SF 和 CD 组方面显示出中等性能（AUC = 0.707， p #x3c；0.001）并且在区分 SF 和 OF 组方面没有显示出统计学上显着的结果（AUC = 0.594， p = 0.080）。CD 组的鼓膜顺应性明显高于 SF 组 ( p = 0.001)。结论： Carhart 切迹不是 SF 的特定发现。ABG 在 2,000 Hz 时≤15 dB 区分 SF 和 CD 的灵敏度和特异性分别为 60.4% 和 89.2%。为了准备对鼓膜正常的传导性听力损失患者进行手术干预，临床医生应综合考虑这些结果。
听觉神经醇