Electrophysiological and histomorphological changes of cochlea in miniature pigs after abrasion of round window niches

Abstract

Background: In operations of cochlea implantation (CI), many surgeons choose to drill a window on the bone wall of cochlea basic rotation, when more and more patients receive CI with residual hearing, what damage this step would result in is unclear.

Objective: To study the effect to inner ear hair cells which is caused by drilling during CI.

Methods: 6 miniature pigs are equally divided into two groups, Round window niche of each pig in the experimental group was milled, while the pigs in control group wasn’t. After implanting depth of 6.5, 11.5 and 20 mm, round window electrocochleography was recorded to analyze the change of cochlea microphonic (CM) potentials respectively, histomorphological changes was observed.

Results: Thresholds of CM in experimental group were higher than that of control group at different depth, amplitudes were smaller. In further group, cilia of inner hair cells (IHC) at bottom rotation were significantly damaged. After operation, ABR hearing threshold of experimental group was higher, differences at low frequency region were more obvious.

Conclusions: Damage caused by mulling round window niche may seriously affect the function of the hair cells. Damage of the IHC is greater than OHC. CI through round window may protect residual hearing.

Chinese abstract

背景：随着越来越多带有残留听力的患者接受CI, 在进行耳蜗植入术（CI）过程中, 许多外科医生选择在耳蜗的底部旋蜗的骨壁钻孔。此步骤将导致何种损害目前尚不清楚。

目的：研究CI过程中钻孔对内耳毛细胞的影响。

方法：将6头小型猪均分两组, 实验组每只猪的圆窗壁龛被碾磨, 而对照组则没有。当植入深度为6.5、11.5和20 mm时, 记录圆窗耳蜗电图以分析耳蜗微音（CM）电位的变化。观察到组织形态学变化。

结果：在不同深度, 实验组CM阈值均高于对照组, 且振幅较小。在另一组中, 底部旋蜗的内毛细胞的纤毛严重损坏。手术后, 实验组的ABR听力阈值较高, 低频区域的差异更为明显。

结论：圆窗壁龛的碾磨导致的损害可能会严重影响毛细胞的功能。 IHC的损害大于OHC。通过圆窗植入人工耳蜗可能会保护残余听力。

Keywords:

• Cochlea microphonic potential
• cochlea implantation
• hair cell injury
• miniature pig

Acknowledgements

We would like to thank the Center for Biological Imaging (CBI), Institute of Biophysics, Chinese Academy of Science for our Dual-beam Scanning Electron Microscopy work, and we would be grateful to Xing Jia for her help of taking SEM images.

Disclosure statement

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

Additional information

Funding

This study was supported by the National Natural Science Foundation of China [NSFC #81970890]. National Key research and development program of China [2020YFC2005200].