The role of preoperative computerized tomography in a safe posterior tympanostomy for cochlear implant surgery.

Introduction: A posterior tympanostomy is a technique performed to access round window area in order to insert cochlear implant electrode into round window membrane or through relationships between the facial nerve (FN) (vertical part), chorda tympani Nerve(CHTN), and facial recess (FR) pneumatization and airations in an axial temporal bone computerized tomography (CT) to be more accurate and safe in performing mastoid surgery with posterior Tympanostomy act. Patient and methods: Retrospective analytic study was established on temporal bone computerized tomography (CT scan)51 patients in a cohort research study, who underwent cochlear implantation with classical mastoidectomy with posterior tympanostomy in our inclusions. Results: 51 patients had a diagnostic CT preoperatively for the temporal bone in-between the period of January 2014 until the end of the study in November 2015. we classified the correlation in the anatomy according to several parameters and factors including the FN protrusion inside mastoid antrum, FR pneumatization, And the status of FN bonny canal. Anatomical relationships between the vertical Part and PT were classified into 3 categories: type 1, the FN has no protrusion with a regular bonny FN canal with pneumatized FR; type 2, the FN is protruded into the mastoid antrum with a regular bonny facial canal and/or poorly pneumatized FR; and type 3, the FN has sclerotic mastoid with no FR pneumatization. Conclusion; These results enable preoperative evaluation of the FN's status and difficulty while performing posterior tympanotomy, providing basic knowledge to prevent injury to the FN while performing a posterior tympanotomy. [ABSTRACT FROM AUTHOR]