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Original Investigation
September 2016

The Effect of Round Window vs Cochleostomy Surgical Approaches on Cochlear Implant Electrode PositionA Flat-Panel Computed Tomography Study

Author Affiliations
  • 1Medical student, Johns Hopkins University School of Medicine, Baltimore, Maryland
  • 2Department of Otolaryngology–Head and Neck Surgery, University of California San Francisco School of Medicine
  • 3Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, Maryland
JAMA Otolaryngol Head Neck Surg. 2016;142(9):873-880. doi:10.1001/jamaoto.2016.1512

Importance  The round window insertion (RWI) and cochleostomy approaches are the 2 most common surgical techniques used in cochlear implantation (CI). However, there is no consensus on which approach is ideal for electrode array insertion, in part because visualization of intracochlear electrode position is challenging, so postoperative assessment of intracochlear electrode contact is lacking.

Objective  To measure and compare electrode array position between RWI and cochleostomy approaches for CI insertion.

Design, Setting, and Participants  Retrospective case-comparison study of 17 CI users with Med-El standard-length electrode arrays who underwent flat-panel computed tomography scans after CI surgery at a tertiary referral center. The data was analyzed in October 2015.

Exposures  Flat-panel computed tomography scans were collected between January 1 and August 31, 2013, for 22 electrode arrays. The surgical technique was identified by a combination of operative notes and imaging. Eight cochleae underwent RWI and 14 cochleae underwent cochleostomy approaches anterior and inferior to the round window.

Main Outcomes and Measures  Interscalar electrode position and electrode centroid distance to the osseous spiral lamina, lateral bony wall, and central axis of the modiolus.

Results  Nine participants were men, and 8, women; the mean age was 54.4 (range, 21-64) years. Electrode position was significantly closer to cochlear neural elements with RWI than cochleostomy approaches. Between the 2 surgical approaches, the RWI technique produced shorter distances between the electrode and the modiolus (mean difference, −0.33 [95% CI, −0.29 to −0.39] mm in the apical electrode; −1.42 [95% CI, −1.24 to −1.57] mm in the basal electrode). This difference, which was most prominent in the first third and latter third of the basal turn, decreased after the basal turn.

Conclusions and Relevance  The RWI approach was associated with an increased likelihood of perimodiolar placement. Opting to use RWI over cochleostomy approaches in CI candidates may position electrodes closer to cochlear neural substrates and minimize current spread. These findings need to be interpreted in light of the increased potential for osseous spiral lamina trauma with reduced distances between the electrode array and modiolus.