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Human Otopathologic Findings in Cases of Folded Cochlear Implant Electrodes

Trakimas, Danielle R.*,†,‡; Kozin, Elliott D.*,†; Ghanad, Iman*,†; Nadol, Joseph B. Jr.*,†; Remenschneider, Aaron K.*,†,‡,§

doi: 10.1097/MAO.0000000000001886

Hypothesis: We hypothesize that human cases of cochlear implantation (CI) with folding of the electrode array will demonstrate greater degrees of intracochlear ossification, lower spiral ganglion neuron (SGN) counts, and poorer audiometric outcomes.

Background: CI electrode array folding, such folding of the proximal array, is a relatively common surgical complication that can occur with forceful electrode insertion and may be an important and avoidable factor affecting implant outcomes. However, otopathologic findings and audiologic outcomes of human cases where folding of the implant electrode array is observed remain undefined.

Methods: Specimens from a human temporal bone repository having undergone CI during life were evaluated. Specimens with folding of the electrode array on histological analysis constituted study cases. Electrode-matched specimens without array folding constituted controls. All specimens were examined by light microscopy and histopathologically described. Intracochlear fibrosis and osseous tissue, and SGN counts were measured. Pre- and postoperative word recognition scores were also compared.

Results: Cases with folded electrodes showed greater volumes of intracochlear osseous tissue than controls, which was most prominent in areas adjacent to array folding. Both cases and controls demonstrated similar amounts of fibrous tissue. Folded cases showed decreased SGNs when compared with the contralateral ear, whereas controls showed stable SGN populations between ears. In this small cohort, postoperative hearing outcomes were similar between groups.

Conclusion: Atypical fibro-osseous changes and lower SGN counts are observed in cases of CI electrode folding. Future studies are necessary to determine if recognition and correction of folding can prevent long-term intracochlear changes.

*Department of Otolaryngology, Massachusetts Eye and Ear Infirmary

Department of Otolaryngology, Harvard Medical School, Boston

University of Massachusetts Medical School

§Department of Otolaryngology, UMass Memorial Medical Center, Worcester, Massachusetts

Address correspondence and reprint requests to Dr. Aaron K. Remenschneider, M.D., Massachusetts Eye and Ear Infirmary, 243 Charles Street, Boston, MA 02114; E-mail:

Level of Evidence: Retrospective review.

Grant Support: NIDCD (NIH) Grant # 2R01-DC000152.

The authors disclose no conflicts of interest.

Copyright © 2018 by Otology & Neurotology, Inc. Image copyright © 2010 Wolters Kluwer Health/Anatomical Chart Company