Cone Beam vs MDCT for Diagnosis and Pre-operative Evaluation of Otosclerosis (CONBEAM OTO)

This study aims to compare the Cone Beam and the multi-detector computed tomography for diagnosis and pre-operative evaluation of otosclerosis in patients addressed for conductive hearing loss with intact tympanic membrane. The study aims to show that the Cone Beam offers equivalent performances with lower radiation dosage in this indication

Otosclerosis is an inflammatory bone remodeling disorder of the otic capsule, characterized by spongiotic new bone formation, causing stamped ankylosis that can result in conductive hearing loss. Until now, the gold standard imaging technique for diagnosis and pre-operative evaluation of otosclerosis has been multi-detector computed tomography (MDCT). Cone Beam computed tomography is a relatively recent imaging modality. It is associated with a lower radiation dosage compared to MDCT, and a high spatial resolution that allows a more precise analysis of bone structures. During the last 15 years, its use has been increasingly common in odontology and craniofacial surgery. Several studies have already studied the utility of Cone Beam for temporal bone pathologies, including recent retrospective studies that showed satisfying diagnostic performances for otosclerosis. Up to now, very few prospective studies have compared those two imaging modalities for otosclerosis diagnosis and pre-operative evaluation. Therefore, those two exams will be performed in patients addressed to the hospital for conductive hearing loss with intact tympanic membrane. Thus, the performance of Cone Beam will be compared to MDCT, regarding the positive diagnosis of otosclerosis, the analysis of anatomical structures of the temporal bone for pre-operative evaluation, and also the benefits in terms of irradiation. The MDCTs will include fewer slices than routine MDCTs and will be centered on the area of interest, in order to keep a total radiation dosage smaller or equivalent to routine care

False negative rate of Cone Beam for the diagnosis of otosclerosis, compared to MDCT (gold standard).

The parameter that will be assessed is the presence/absence of a bony hypodensity located on the round window bony structure . CT will be considered as gold standard. CBCT may be less or equally accurate to detect this small hypodensity area structure

The parameter that will be assessed is the presence /absence of a bony structure covering the VIIth nerve a the level of the oval window. CT will be considered as gold standard. CBCT may be less or equally accurate to detect this very thin bony structure , or even better in case of better detection

Inclusion Criteria: Adult patients (18 years and older) Requiring radiological assessment for conductive hearing loss with intact tympanic membrane, confirmed by otoscopy and audiogram Signed informed consent Affiliated or beneficiary of health insurance Exclusion Criteria: Absence of otosclerosis on the MDCT History of middle ear surgery Pregnancy, breast feeding women and women who are of childbearing age and not practicing adequate birth control Patient under legal protection