Three-dimensional finite-element analysis of the cochlear hypoplasia

Abstract

Objectives: Based on CT scan images of healthy human ear, the effects of cochlear hypoplasia on auditory functions was studied.

Methods: Three-dimensional nonlinear finite-element numerical model was developed and used to predict frequency responses of hypoplastic cochleae. The numerical model was validated by comparing the modeling results to reported experimental data.

Results: The cochlear hypoplasia compromises sound conduction of middle ear and results in significant decrease of vibration displacement amplitude of stapes foot-plate at frequencies 100 ∼ 1200 Hz with a maximal decrease of 9.1 dB at ∼1000 Hz. Consequently, the displacement ratio of basement membrane vibration at the longitudinal location ∼12 mm from the apex to the stapes vibration decreases at 100 ∼ 4000 Hz with the biggest decrease of 15.2 dB at ∼ 4000 Hz.

Conclusions: Numerical modeling was used to demonstrate the effect of cochlear hypoplasia on sound conduction and cochlear sensitivity. Cochlear hypoplysia causes changes in biomechanics of middle ear and inner ear, which lead to hearing loss. The current modeling results suggest that the frequency-dependent decrease of the stapes vibration can be used in clinics for diagnosing cochlear hypoplasia. This is particularly important because the middle ear function measurement can be used to diagnose unmeasurable inner ear disorders.

Chinese abstract

目的：根据健康人耳的CT扫描图像, 研究耳蜗发育不全对听觉功能的影响。

方法：建立三维非线性有限元数值模型, 将之用于预测发育不全耳蜗的频率回应。通过比较模拟结果和实验数据, 验证了数值模型的正确性。

结果：耳蜗发育不全影响中耳的声传导, 导致镫骨脚板在100∼1200赫兹频率下振动位移幅度显著降低, 在∼1000赫兹频率下振动位移幅度降低最多, 达9.1分贝。因此, 从顶点到镫骨纵向位置约12 mm处基底膜振动的位移比在100∼4000 Hz时减小, 在∼4000 Hz时减小量最大, 达15.2 分贝。

结论：采用数值模拟方法来显示耳蜗发育不全对声传导和耳蜗敏感性的影响。耳蜗发育不全引起中耳和内耳的生物力学改变；后者导致听力下降。目前的模拟结果表明, 镫骨振动的频率依赖性降低可用于耳蜗发育不全的临床诊断。这一点尤为重要, 因为中耳功能测量可用于诊断不可测量的内耳疾病。

Keywords:

• Cochlear hypoplasia
• numerical modeling
• dynamic response
• hearing
• basilar membrane vibration

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This study was supported by National Natural Science Foundation Project of China under number 11272200, 11572186.