Volume 134, Issue 2 pp. 945-953
Original Report

Human Histology after Structure Preservation Cochlear Implantation via Round Window Insertion

Alexander Geerardyn MD

Alexander Geerardyn MD

Department of Otolaryngology—Head & Neck Surgery, Harvard Medical School, Boston, Massachusetts, U.S.A.

Otopathology Laboratory, Massachusetts Eye and Ear, Boston, Massachusetts, U.S.A.

ExpORL, Department of Neurosciences, Katholieke Universiteit Leuven, Leuven, Belgium

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MengYu Zhu MS

MengYu Zhu MS

Otopathology Laboratory, Massachusetts Eye and Ear, Boston, Massachusetts, U.S.A.

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Tim Klabbers MD

Tim Klabbers MD

Department of Otorhinolaryngology, Radboudumc, Nijmegen, the Netherlands

Donders Institute for Brain, Cognition and Behaviour, Nijmegen, the Netherlands

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Wendy Huinck PhD

Wendy Huinck PhD

Department of Otorhinolaryngology, Radboudumc, Nijmegen, the Netherlands

Donders Institute for Brain, Cognition and Behaviour, Nijmegen, the Netherlands

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Emmanuel Mylanus MD, PhD

Emmanuel Mylanus MD, PhD

Department of Otorhinolaryngology, Radboudumc, Nijmegen, the Netherlands

Donders Institute for Brain, Cognition and Behaviour, Nijmegen, the Netherlands

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Joseph B. Nadol Jr MD

Joseph B. Nadol Jr MD

Department of Otolaryngology—Head & Neck Surgery, Harvard Medical School, Boston, Massachusetts, U.S.A.

Otopathology Laboratory, Massachusetts Eye and Ear, Boston, Massachusetts, U.S.A.

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Nicolas Verhaert MD, PhD

Nicolas Verhaert MD, PhD

ExpORL, Department of Neurosciences, Katholieke Universiteit Leuven, Leuven, Belgium

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Alicia M. Quesnel MD

Corresponding Author

Alicia M. Quesnel MD

Department of Otolaryngology—Head & Neck Surgery, Harvard Medical School, Boston, Massachusetts, U.S.A.

Otopathology Laboratory, Massachusetts Eye and Ear, Boston, Massachusetts, U.S.A.

Send correspondence to Alicia M. Quesnel, Department of Otolaryngology—Head & Neck Surgery, Harvard Medical School, Massachusetts Eye and Ear, 243 Charles Street, Boston, MA 02114. Email: [email protected]

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First published: 26 July 2023
Editor's Note: This Manuscript was accepted for publication on July 05, 2023.

Nicolas Verhaert and Alicia M. Quesnel contributed equally to this work and share last authorship.

This work was financially supported by Research Foundation Flanders (FWO: 1SD3322N(AG), V414121N(AG), 1804816N(NV), G088619N(NV)) and NIH (U24DC013983(AMQ), U24DC020849(AMQ)).

Alicia M. Quesnel, MD: Grace Medical—sponsored research agreement; Frequency Therapeutics—sponsored research agreement, consulting; Alcon—consulting. The department of Tim Klabbers MD, Wendy Huinck PhD and Emmanuel Mylanus MD PhD currently receives ongoing institutional grants from Cochlear Ltd. and Oticon Medical but not specifically for this study. The other co-authors have no conflicts of interest to declare.

Abstract

Objectives

Current surgical techniques aim to preserve intracochlear structures during cochlear implant (CI) insertion to maintain residual cochlear function. The optimal technique to minimize damage, however, is still under debate. The aim of this study is to histologically compare insertional trauma and intracochlear tissue formation in humans with a CI implanted via different insertion techniques.

Methods

One recent temporal bone from a donor who underwent implantation of a full-length CI (576°) via round window (RW) insertion was compared with nine cases implanted via cochleostomy (CO) or extended round window (ERW) approach. Insertional trauma was assessed on H&E-stained histological sections. 3D reconstructions were generated and virtually re-sectioned to measure intracochlear volumes of fibrosis and neo-ossification.

Results

The RW insertion case showed electrode translocation via the spiral ligament. 2/9 CO/ERW cases showed no insertional trauma. The total volume of the cochlea occupied by fibro-osseous tissue was 10.8% in the RW case compared with a mean of 30.6% (range 8.7%–44.8%, N = 9) in the CO/ERW cases. The difference in tissue formation in the basal 5 mm of scala tympani, however, was even more pronounced when the RW case (12.3%) was compared with the cases with a CO/ERW approach (mean of 93.8%, range 81% to 100%, N = 9).

Conclusions

Full-length CI insertions via the RW can be minimally traumatic at the cochlear base without inducing extensive fibro-osseous tissue formation locally. The current study further supports the hypothesis that drilling of the cochleostomy with damage to the endosteum incites a local tissue reaction.

Level of Evidence

4: Case–control study Laryngoscope, 134:945–953, 2024

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