Cochlear Implantation With a Novel Long Straight Electrode: the Insertion Results Evaluated by Imaging and Histology in Human Temporal Bones.

HYPOTHESIS: To evaluate the insertion results of a novel straight array (EVO) by detailed imaging and subsequent histology in human temporal bones (TB).

BACKGROUND: The main focuses of modern cochlear implant surgery are to prevent damage to the intracochlear structures and to preserve residual hearing. This is often achievable with new atraumatic electrode arrays in combination with meticulous surgical techniques.

METHODS: Twenty fresh-frozen TBs were implanted with the EVO. Pre- and postoperative cone beam computed tomography scans were reconstructed and fused for an artifact-free representation of the electrode. The array's vertical position was quantified in relation to the basilar membrane on basis of which trauma was classified (Grades 0-4). The basilar membrane location was modeled from previous histologic data. The TBs underwent subsequent histologic examination.

RESULTS: The EVOs were successfully inserted in all TBs. Atraumatic insertion (Grades 0-1) were accomplished in 14 of 20 TBs (70%). There were three apical translocations, and two basal translocations due to electrode bulging. One TB had multiple translocations. The sensitivity and specificity of imaging for detecting insertion trauma (Grades 2-4) was 87.5% and 97.3.0%, respectively.

CONCLUSION: Comparable insertion results as reported for other arrays were also found for the EVO. Insertion trauma can be mostly avoided with meticulous insertion techniques to prevent bulging and by limiting the insertion depth angle to 360 degrees. The image fusion technique is a reliable tool for evaluating electrode placement and is feasible for trauma grading.