The aim of the study is to identify the scannographic criterion the most relevant to predict the round window visibility during cochlear implantation.

Whereas several surgical techniques exist to perform a cochlear implantation, the most used is the realization of mastoidectomy followed by posterior tympanotomy, in order to expose the round window, which finally permits to access to the cochlea. This procedure might be complicated with facial paresis, loss of residual hearing, because of anatomy relationships in this millimetric area.

CT scan of temporal bone is part of systematic preoperative assessment. Technological advances in radiology during the last decades now provide inframillimetric resolution. Thus, otologic surgeons wish they could anticipate round window exposure from these CT scan. This could decrease the procedure duration, complication occurrence, or improve surgical strategy.

Several studies proposed radiological criteria in this aim, from more or less complex measures in preoperative temporal bone CT scan. However, these diagnostic tests performances have not been assessed for most of them, or compared between them.

inclusion criteria :

• patients undergoing cochlear implantation in Reims universitary hospital during the inclusion period
• patients who agree to participate in the study
• patients who had preoperative temporal bone CT scan

exclusion criteria : patients who have :

• temporal bone malformation on temporal bone CT scan or MRI
• chronic otitis media (except simple middle ear effusion)
• middle ear surgery antecedent
• cochlear implant in the context of a reimplantation

Patients with cochlear implantation