The role of high-resolution Computer Tomography in prediction of the round window membrane visibility and the feasibilit
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OTOLOGY
The role of high‑resolution Computer Tomography in prediction of the round window membrane visibility and the feasibility of the round window electrode insertion Saad Elzayat1 · Islam Soltan1 · Mona Talaat2 · Yasser Ahmed Fouad3 Received: 9 June 2020 / Accepted: 30 September 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Objective The aim of this work is to assess the role of pre-operative high-resolution computerized tomography (HRCT) in prediction of the round window membrane (RWM) visibility and the feasibility of round window electrode insertion. Materials and methods Retrospective study on a series of 97 cases of cochlear implant (CI) who were implanted in tertiary referral centers. We reviewed HRCTof all cases, and we implicated two radiological measurements on HRCT which are membrano-facial angle (MFA) and length of the bony overhang of the round window niche (RWN). We reviewed the intraoperative surgical video recordings of all cases for detection of the type of RWM visibility, according to The St Thomas’ Hospital classification. Results The MFA was 21.9 ± 14.5. The length of the bony overhang of the RWN was 2.4 ± 0.33 mm. About 37% of the studied patients needed cochleostomy. The best cut-off of MFA in the prediction of the RW (type 2B and 3) was ≥ 15.1o with sensitivity 100%, and specificity 82%. Conclusion HRCT offers highly reliable and reproducible measurements for the prediction of RWM visibility and, therefore, prediction of the utility of the RW approach for electrode insertion. Membrano-facial angle (MFA) is a new measurement that can be used for this purpose. Keywords Cochlear implant · HRCT · St thomas’ hospital classification · Round window membrane · Round window approach
Introduction Cochlear implant (CI) has become the standard management for patients with hearing sever to profound sensory-neural hearing loss [1]. Outcomes of CI are influenced by extrinsic and intrinsic factors. Intrinsic factors include the duration of hearing loss, cochlear nerve diameter, and the degree of residual hearing The work was done in Otolaryngology Departments and Cochlear Implant Referral Institutes, Egypt. * Islam Soltan [email protected]; [email protected] 1
ENT Department, Kafrelsheikh University, Kafrelsheikh, Egypt
2
Radiology Department, Kafrelsheikh University, Kafrelsheikh, Egypt
3
ENT Department, Zagazig University, Zagazig, Egypt
[2]. Extrinsic factors include mainly various surgical maneuvers that influence the possibility of hearing preservation during cochlear implant, including electrode design, surgical tichnique, insertion trauma, and steroid usage [3]. Albeit the optimal surgical approach for electrode insertion is highly debated, electrode implantation via the RWM minimizes intra-cochlear trauma and new tissue formation, while other methods of cochleostomy may results in more damage to the neurosensetive structures within the cochlea [4]. Furthermore, the cochleostomy approach is associated with a higher rate of inter-scal
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