A Mid-scala Cochlear Implant Electrode Design Achieves a Stable Post-surgical Position in the Cochlea of Patients Over Time—A Prospective Observational Study

Introduction: Cochlear implant (CI) electrode design impacts the clinical performance of patients. Stability and the occurrence of electrode array migration, which is the postoperative movement of the electrode array, were investigated using a mid-scalar electrode array and postoperative image analysis. Methods: A prospective observational study was conducted. A mid-scalar electrode was surgically placed using a mastoidectomy, followed by a posterior tympanotomy and an extended round-window or cochleostomy insertion. A few days after surgery and 3 months later Cone Beam Computed Tomography (CBCT) was performed. The two different CBCT's were fused, and the differences between the electrode positions in three dimensions were calculated (the migration). A migration greater than 0.5 mm was deemed clinically relevant. Results: Fourteen subjects participated. The mid-scalar electrode migrated in one patient (7%). This did not lead to the extrusion of an electrode contact. The mean migration of every individual electrode contact in all patients was 0.36 mm (95% confidence interval 0.22–0.50 mm), which approximates to the estimated measurement error of the CBCT technique. Conclusion: A mid-scalar electrode array achieves a stable position in the cochlea in a small but representative group of patients. The methods applied in this work can be used for providing postoperative feedback for surgeons and for benchmarking electrode designs. Address correspondence and reprint requests to Guido Dees, M.Sc., M.D., Department of Department of Otorhinolaryngology and Head and Neck Surgery, Maastricht University Medical Center, PO Box 5800, 6202 AZ Maastricht, The Netherlands; E-mail: guidodees@gmail.com Financial Disclosures/Conflicts of Interest: We acknowledge a research grant from Advanced Bionics Inc., which financially supported the work in this investigator-initiated study. The third author (M.J.) provided statistical support, made possible by a grant from the Dutch Heinsius-Houbolt Foundation. The fifth author is a paid employee of Advanced Bionics Inc. The authors disclose no other conflicts of interest. Copyright © 2018 by Otology & Neurotology, Inc. Image copyright © 2010 Wolters Kluwer Health/Anatomical Chart Company

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