Abstract
Problem
To investigate the relationship between the intrusion of the air bubble into the scala vestibli and hearing loss at low frequencies.
Methods
The effect of intrusion of an air bubble into the scala vestibuli on auditory activity was analyzed based on clinical data and using a three-dimensional finite element (FE) model of the human cochlea. The FE model consists of the stapes, the stapedial annular ligament, the oval window, vestibule, lymph, basilar membrane, osseous spiral lamina, and the cochlear aqueduct. An air bubble in the scala vestibuli was modeled as a small fistula opened on the bony wall of the cochlea. The induced vibration of the lymph and the basilar membrane was calculated by changing the position of the air bubble using CFD-ACE software.
Results
A traversing wave was generated on the basilar membrane of the intact cochlear model by vibrating the stapes. Even if the air bubble existed in the scala vestibuli, the traversing wave was also generated. When the air bubble existed at the second turn of the cochlea, an envelope of the traversing wave had a notch at the portion where the air bubble existed. The ratio of the maximum amplitude of the basilar membrane in the cochlea with the air bubble to that in the intact cochlea decreased with decreasing frequency. The maximum amplitude of the traversing wave in the cochlea with the air bubble was smaller than that in the intact cochlea by 20 dB at 500 Hz. This result is consistent with clinical data.
Conclusion
Our results suggest that the intrusion of an air bubble into the scala vestibuli causes hearing loss at low frequencies.
Significance
The removal of air bubbles into the scala vestibli is needed for hearing improvement.
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