Analysis of tympanic sinus shape for purposes of intraoperative hearing monitoring: a microCT study

Jacek Sokołowski,Tomasz Wojciechowski,Małgorzata Bilińska,Kazimierz Niemczyk

doi:10.1007/s00276-021-02859-7

Jacek Sokołowski, Tomasz Wojciechowski

Open Access

https://doi.org/10.1007/s00276-021-02859-7

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Abstract

PurposeSinus tympani is the space in the retrotympanum, with variable morphology. Computed tomography is a common tool to investigate sinus tympani anatomy. During cochlear implantation or tympanoplasty, electrocochleography can be used for hearing monitoring. In such a surgical strategy the electrode is placed in the round window’s region throughout posterior tympanotomy. Common accessible needle-shaped electrodes using is difficult in achieving intraoperative stabilization. The aim of the study is to assess the dimensions and shape of sinus tympani, basing on the micro computed tomography scans for purposes of establishing the possible new electrocochleography electrode shape.Materials and methodsSixteen fresh frozen cadaveric temporal bones were dissected. MicroCT measurements included the depth and the width of sinus tympani, width of facial canal with stapedius muscle chamber. Obtained data were analyzed statistically with the use of RStudio 1.3.959 software.ResultsThe highest average width of sinus tympani amounted for 2.68 mm, depth measured at the round window plane for 3.19 mm. Width of facial canal with stapedius muscle chamber highest average values at the round window plane- 3.32 mm. The lowest average minimum and maximum values were calculated at the 1 mm above the round window plane. The highest average posterior tympanotomy width was 2.91 mm.ConclusionsThe shape of the tympanic sinus is like a trough with the narrowest and deepest dimensions in the middle part. The ST shape and dimensions should be taken into account in constructing the ECochG electrode, designed for optimal placement through posterior tympanotomy approach.

Highlights

The central structure in the topography of the posterior wall of the tympanic cavity is facial nerve, or rather the corresponding pyramidal ridge
There was possible to perform measurements of the tympanic sinus based on available micro- Computed Tomography
The computed tomography (CT)-scans analysis provided enough information and the anatomical structures such as stapes head, round window, tympanic sinus space were delineated on the CT scan

Summary

Introduction

The central structure in the topography of the posterior wall of the tympanic cavity is facial nerve, or rather the corresponding pyramidal ridge. It divides the posterior wall into lateral and medial spaces. The central point (fulcrum) of the posterior wall, is the pyramidal eminence. Sinus tympani (ST) is considered to be largest space in the retrotympanum. It is located medially to the pyramidal eminence, stapedius muscle, and facial nerve and laterally to the posterior semicircular canal [2, 15, 26]. The sinus is subject to great variability in posterior extent, in some cases,

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