Three-dimensional finite-element analysis of the cochlear hypoplasia

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

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.

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.

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.