A Numerical Study of Fenestral Otosclerosis

There are three basic types of hearing loss: conductive, sensorineural and mixed. Otosclerosis is a pathology which can originate any of these types of hearing loss. Otosclerosis is a bone dysplasia, present only in the temporal bone, and consists of single or multiple absorption areas followed by healing with bone neoformation. The clinical result of this pathology is a conductive deafness when a stapes footplate fixation occurs at the oval window or a sensorineural deafness when it affects the otic capsule involving the cochlear endosteum. Otosclerosis is categorised into two types, fenestral (stapedial type) and retrofenestral (cochlear type). Cochlear otosclerosis represents a continuation of the fenestral otosclerotic process and rarely occurs without fenestral involvement. The numerical model used in this work was build based on the geometrical information obtained from “The visible ear” project. A cryosectioning procedure was applied to the temporal bone of an 85 years old woman, without hearing pathologies, to obtain anatomical data. Afterwards, the different tissues were hand-segmented and a 3D model was constructed. The aim of this study is to contribute to the understanding of the alterations introduced by the fenestral otosclerosis in the human ear and its consequences on the earing capability, using a numerical analysis. The umbo and stapes displacements with the presence of fenestral otosclerosis were carried out for a stimulation of 80 dB SPL applied on the tympanic membrane. The stimulus was applied at frequencies ranging between 100 and 10 kHz. The main conclusion of this work is that the fenestral otosclerosis affects the motion of the stapes footplate, without changing significantly the umbo response.