ENT Institute and Otorhinolaryngology Department, Affiliated Eye and ENT Hospital, Fudan University, Shanghai, China.
Department of Otorhinolaryngology of the First Affiliated Hospital, Anhui Medical University, Hefei, China.
Neural Plast. 2018 Apr 24;2018:1258341. doi: 10.1155/2018/1258341. eCollection 2018.
Defective acoustic transmission in the cochlea is closely related with various auditory and vestibular symptoms. Among them, semicircular canal dehiscence (SCD) with a defective semicircular bone is typical. Currently, the pathogenesis of SCD is usually explained by the third window hypothesis; however, this hypothesis fails to explain the variability in the symptoms and signs experienced by superior SCD (SSCD) patients. We evaluated the mechanism of hearing loss in a guinea pig model of bony dehiscence with various sizes and locations along the superior semicircular canal. Auditory brainstem responses (ABRs) and laser Doppler velocimetry were used to measure hearing loss and vibration changes before and after fenestration, as well as after restorative patching. ABR thresholds at low frequencies (e.g., 1000 Hz) increased after fenestration and decreased back to the normal range after we repaired the defect. Energy leakage from the surgically introduced third window was detected in the range of 300-1500 Hz, accompanied by increased vibration at the umbo, stapes head, and the dehiscence site, while decreased vibration was observed at the round window membrane in the same frequency range. After the patching procedure, the deviant vibrations were recovered. The degree of postfenestration energy leakage was proportional to the size of fenestration and the proximity of the fenestration site to the oval window. These results suggest that the bony fenestration of the superior semicircular canal mimics the hearing loss pattern of patients with SSCD. The decrease in perilymph wave impedance likely accounts for the auditory changes.
耳蜗传音功能障碍与各种听觉和前庭症状密切相关。其中，半规管裂（SCD）伴半规管骨缺损为典型表现。目前，SCD 的发病机制通常用第三窗口假说解释，但该假说无法解释上半规管裂（SSCD）患者症状和体征的可变性。我们评估了沿上半规管不同大小和位置的骨裂兔模型的听力损失机制。应用听性脑干反应（ABR）和激光多普勒测振仪测量开窗前后以及修复后听力损失和振动变化。开窗后低频（如 1000Hz）的 ABR 阈值升高，修复后恢复正常范围。在 300-1500Hz 范围内检测到手术引入的第三窗口的能量泄漏，同时镫骨足板、镫骨头和裂孔处的振动增加，而同一频率范围内圆窗膜的振动减小。修复后，异常振动恢复。术后能量泄漏程度与开窗大小及开窗部位与卵圆窗的接近程度成正比。这些结果表明，上半规管骨开窗可模拟 SSCD 患者的听力损失模式。外淋巴液波阻抗的降低可能是导致听觉改变的原因。
