Department of Otorhinolaryngology, Yonsei University College of Medicine, Seoul, Republic of Korea.
Audiol Neurootol. 2023;28(4):255-261. doi: 10.1159/000528826. Epub 2023 Feb 8.
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.
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.
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 < 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 < 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).
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.
卡哈切迹是镫骨固定的一个著名征象。然而，之前的研究报告称卡哈切迹并非镫骨固定所特有，也存在于其他中耳疾病中。因此，本研究探讨了气导骨导阈差（ABG）对镫骨固定的诊断价值，而不是代表卡哈切迹的骨导谷。
本回顾性研究共纳入 199 耳接受探查性鼓室成形术的患者。根据手术发现将其分为三组：镫骨固定（SF）、其他听小骨固定（OF）和听骨链中断（CD）。比较了各组的术前纯音听力图和阻抗听力图。
各组之间卡哈切迹的发生率无差异。2000Hz 的 ABG 对区分 SF 和 CD 组具有良好的诊断性能（曲线下面积，AUC=0.816，p<0.001），但对区分 SF 和 OF 组的性能较差（AUC=0.662，p=0.003）。2000Hz 的骨导对区分 SF 和 CD 组具有中等性能（AUC=0.707，p<0.001），对区分 SF 和 OF 组的结果无统计学意义（AUC=0.594，p=0.080）。CD 组的鼓膜顺应性明显高于 SF 组（p=0.001）。
卡哈切迹不是 SF 的特异性表现。2000Hz 的 ABG≤15dB 对区分 SF 和 CD 的敏感性和特异性分别为 60.4%和 89.2%。对于患有传导性听力损失但鼓膜正常的患者，为准备手术干预，临床医生应综合考虑这些结果。
