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Effects of Various Trajectories on Tissue Preservation in Cochlear Implant Surgery

A Micro-Computed Tomography and Synchrotron Radiation Phase-Contrast Imaging Study

Schart-Morén, Nadine1; Agrawal, Sumit K.2,3,4; Ladak, Hanif M.2,3,4; Li, Hao1; Rask-Andersen, Helge1

doi: 10.1097/AUD.0000000000000624
Research Article: PDF Only

Objectives: The purpose of this study was to evaluate the three-dimensional (3D) anatomy and potential damage to the hook region of the human cochlea following various trajectories at cochlear implantation (CI). The goal was to determine which of the approaches can avoid lesions to the soft tissues, including the basilar membrane and its suspension to the lateral wall. Currently, there is increased emphasis on conservation of inner ear structures, even in nonhearing preservation CI surgery.

Design: Micro-computed tomography and various CI approaches were made in an archival collection of macerated and freshly fixed human temporal bones. Furthermore, synchrotron radiation phase-contrast imaging was used to reproduce the soft tissues. The 3D anatomy was investigated using bony and soft tissue algorithms, and influences on inner ear structures were examined.

Results: Micro-computed tomography with 3D rendering demonstrated the topography of the round window (RW) and osseous spiral laminae, while synchrotron imaging allowed reproduction of soft tissues such as the basilar membrane and its suspension around the RW membrane. Anterior cochleostomies and anteroinferior cochleostomies invariably damaged the intracochlear soft tissues while inferior cochleostomies sporadically left inner ear structures unaffected.

Conclusions: Results suggest that cochleostomy approaches often traumatize the soft tissues at the hook region at CI surgery. For optimal structural preservation, the RW approach is, therefore, recommended.

1Department of Surgical Sciences, Otorhinolaryngology, Head and Neck Surgery, Uppsala University, Uppsala, Sweden;

2Department of Otolaryngology-Head and Neck Surgery, Western University, London, Ontario, Canada;

3Department of Medical Biophysics, Western University, London, Ontario, Canada; and

4Department of Electrical and Computer Engineering, Western University, London, Ontario, Canada.

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ACKNOWLEDGMENTS: This study was supported by ALF grants from Uppsala University Hospital and Uppsala University and by the Foundation of “Ingrid Löwenström” and kind private funds from Börje Runögård and David Giertz, Sweden. Part of the research described in this paper was performed at the BMIT facility at the Canadian Light Source, which is funded by the Canada Foundation for Innovation, the Natural Sciences and Engineering Research Council of Canada, the National Research Council Canada, the Canadian Institutes of Health Research, the Government of Saskatchewan, Western Economic Diversification Canada, and the University of Saskatchewan.

S.K.A. and H.M.L. are co-senior authors.

The authors have no conflicts of interest to disclose.

Address for correspondence: Nadine Schart-Morén, Department of Surgical Sciences, Otorhinolaryngology, Head and Neck Surgery, Uppsala University, SE-751 85, Uppsala, Sweden. E-mail:

Received December 15, 2017; accepted April 27, 2018.

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