Skip to main content

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


A posterior tympanotomy is a technique performed to access round window area to insert cochlear implant electrode into round window membrane or through cochleostomy. In this study, we aimed to classify and evaluate the anatomical relationships between the facial nerve (FN) (vertical segment), chorda tympani nerve, and facial recess (FR) pneumatization in an axial temporal bone computerized tomography (CT) to be safe when performing a posterior tympanotomy. We performed a retrospective analytic study of temporal bone CT scans. A cohort of 51 patients who underwent cochlear implantation with classical mastoidectomy with posterior tympanotomy were included. All patients had preoperative diagnostic CT of the temporal bone from January 2014 to November 2015. Anatomical correlations were classified according to several parameters including protrusion of the FN into the antrum, FR pneumatization, and status of the facial canal. 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 with pneumatized FR; type 2, the FN has protrusion into the antrum with a regular facial canal and/or poorly pneumatized FR; and type 3, the FN has sclerotic mastoid with no FR pneumatization. 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.


  1. 1

    Jako GJ. The posterior route to the middle ear: posterior tympanotomy. Laryngoscope 1977; 77:306–316.

    Article  Google Scholar 

  2. 2

    Roberts DM, Bush ML, Jones RO Adult progressive sensorineural hearing loss: is preoperative imaging necessary before cochlear implantation? Otol Neurotol 2014; 35:241–245.

    Article  Google Scholar 

  3. 3

    Kashio A, Sakamoto T, Karino S, Kakigi A, Iwasaki S, Yamasoba T. Predicting round window Niche visibility via the facial recess using high-resolution computed tomography. Otol Neurotol 2015; 36:18–23.

    Google Scholar 

  4. 4

    Green JD, Shelton C, Brackmann DE. Iatrogenic facial nerve injury during otologic surgery. Laryngoscope 1994; 104:922–926.

    PubMed  Google Scholar 

  5. 5

    Luntz M, Malatskey S, Braun J. The anatomic relationshipbetween the second genu of the facial nerve and the incus: a highresolution computed tomography study. Am J Otol 2000; 21:686–689.

    CAS  PubMed  Google Scholar 

  6. 6

    Swartz JD. The facial nerve canal: CT analysis of the protruding tympanic segment. Radiology 1984; 153:443–447.

    CAS  Article  Google Scholar 

  7. 7

    Aslan A, Goktan C, Okumus M, Tarhan S, Unlu H. Morphometric analysis of anatomical relationships of the facial nerve for mastoid surgery. J Laryngol Otol 2001; 115:447–449.

    CAS  Article  Google Scholar 

  8. 8

    Wetmore SJ. Surgical landmarks for the facial nerve. Otolaryngol Clin North Am 1991; 24:505–530.

    CAS  Article  Google Scholar 

  9. 9

    Nager GT, Proctor B. Anatomic variations and anomalies involving the facial canal. Otolaryngol Clin North Am 1991; 24:531–553.

    CAS  Article  Google Scholar 

  10. 10

    Fowler EP. Variations in the temporal bone course of the facial nerve. Laryngoscope 1961; 71:937–944.

    Article  Google Scholar 

  11. 11

    Baxter A. Dehiscence of the fallopian canal: an anatomical study. J Laryngol Otol 1971; 85:587–594.

    CAS  Article  Google Scholar 

Download references

Author information



Corresponding author

Correspondence to Saad Elzayat.

Additional information

This is an open access article distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 License, which allows others to remix, tweak, and build upon the work non-commercially, as long as the author is credited and the new creations are licensed under the identical terms.

Rights and permissions

This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Elzayat, S., Mandour, M. & Lotfi, R. The role of preoperative computerized tomography in a safe posterior tympanotomy for cochlear implant surgery. Egypt J Otolaryngol 33, 569–572 (2017).

Download citation


  • cochlear implant
  • computed tomography
  • facial nerve
  • posterior tympanotomy