Intraoperative Evaluation of Cochlear Implant Electrodes Using Mobile Cone-Beam Computed Tomography

Objective: To evaluate the electrode status during cochlear implantation (CI) using mobile cone-beam CT (mCBCT). Study Design: Retrospective case review. Setting: Tertiary referral hospital. Patients: Fifty-seven patients (7 bilateral surgeries, 64 ears) who underwent CI and who received intraoperative mCBCT imaging. Intervention: CI and CBCT during surgery. Main Outcome Measure: Electrode location and angular insertion depth determined by intraoperative mCBCT images. Results: There were six cases with cochlear malformation where intraoperative mCBCT was useful to confirm electrode location. Of 58 ears with a normal cochlear morphology, perimodiolar, straight, and mid-scalar electrodes were used in 30 (cochleostomy; 14 advance off-stylet technique cases), 27 (26 round window [RW] insertion, 1 extended round window [ERW] insertion), and 1 (RW insertion) ears, respectively. Complete scala-tympani (ST) insertion was achieved in 35 ears (14 cochleostomy, 21 RW or ERW insertion). The complete ST-insertion rate was significantly higher with RW or ERW insertion than that for cochleostomy insertion (p = 0.03), although cochleostomy insertion using the advanced off-stylet technique had a similar rate to RW or ERW insertion. The angular insertion depth values (average +/- standard deviation) for perimodiolar electrodes (354.4 +/- 29.44 degrees) were significantly smaller than those for Flex24 (464.8 +/- 43.09 degrees) and Flex28 (518.2 +/- 61.91 degrees) electrodes (p < 0.05). Conclusions: Evaluation of CI electrodes using intraoperative mCBCT was comparable to that with fan-beam CT or c-arm-based CBCT. Considering the low radiation dose of mCBCT and its availability in any operation room, mCBCT is the better modality for evaluating cochlear implant electrode arrays.