Bone conduction hearing in congenital aural atresia.

Previous researches focusing on BC hearing mechanisms proved that the two routes, (1) EAC sound radiation and (2) inertial of ossicular chain, partially contribute to normal BC hearing. Therefore, the BC hearing for those patients with congenital aural atresia should partially decrease theoretically due to their abnormal anatomy. However, there are not many studies which mention these patients' BC hearing up till now. The objective of this study is to investigate congenital aural atresia patient's BC hearing by analysis of pre-surgical audiogram and to study their potential BC hearing mechanisms using animal modeling and their ABR measurements. The study methoed involves analyzing 75 patients' pre-operative audiogram. Then we produced an animal model by surgery to measure their BC hearing threshold changes. Clinical data showed that those patients had some BC hearing loss; and there were 25 cases (25/75, 33.3 %) which present with typical Carhart's Notch. The animal experiments proved that inertia of ossicular chain contribute to partial BC hearing, which demonstrated that the inertia produced more affects on high frequencies by comparing with low frequencies. The patients with congenital aural atresia present BC hearing loss, which could be mainly ascribed to the absence of inertia of ossicular chain.