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Aposteriortympanostomy is a technique to proper access round window area to insert cochlear implant electrode into round window (RW ) membrane or through cochleostomy. We aimed in this research to classify with evaluation the anatomical relations in between facial nerve (FN)(vertical part), chorda tympani nerve, facial recess (FR)pneumatization inanaxialtemporal bone computerized tomography (CT) to be safe when posterior tympanotomy will be operated. A retrospective analytic study was established of the petrous bone CT scans .51 patients who prepared to cochlear implantation (CI)with classical mastoidectomy with posterior tympanotomy were included in this cohort study.Preoperative diagnostic CT of the petrous bones for all cases from January 2014 to November 2015.Correlations in anatomical variations were classified by several parameters including FN protrusion into the mastoid antrum, FR pneumatization, and the facial canal integrity.Anatomical relationships between the vertical segment and posterior tympanotomy were classified into three types: type 1, the FN has no protrusion with a regular facial canal withpneumatized FR; type 2,theFNis protruded into the mastoid antrum within canal within regular manner and/or poorly pneumatized FR;andtype3,theFNhassclerotic mastoid with noFRpneumatization. These results enable preoperative evaluation of the FN's status and difficulty while performing posterior tympanotomy, providing basic knowledge to prevent injury of the FN while performing a posterior tympanotomy. [ABSTRACT FROM AUTHOR]

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]