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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 (seven bilateral surgeries, sixty-four ears) who underwent cochlear implantation (CI) and took the intra-operative mCBCT images. Twenty- nine patients were less than 10 years old (mean age: 2.9 years old). Intervention: Cochlear implantation and CBCT during surgery Main outcome measure: The electrode location and angular insertion depth (AID) determined by intra-operative mCBCT images. Results: Seven were cochlear malformation cases where intra-operative mCBCT was useful to confirm the electrode location. Among 58 ears with normal cochlear morphology, perimodiolar, slim straight and mid-scalar electrodes were used in 30 (cochleostomy, 14 advance off-stylet technique cases), 27 (26 round window (RW) and one extended round window (ERW) insertion), and 1 (RW insertion) cases, respectively. Complete scala-tympani (ST) insertion was achieved in 35 cases (fourteen cochleostomy and 21 RW or ERW cases). The complete ST-insertion rate was significantly higher in the RW or ERW insertion than cochleostomy insertion (p=0.03). The AID 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 results of the CI electrodes by intra- operative mCBCT were comparative to those utilizing 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 selection as a modality to evaluate CI electrodes. [ABSTRACT FROM AUTHOR]

Facial nerve stimulation is one of well-known complications in surgery of cochlear implantation in advanced cochlear otosclerosis. Here we present a case where intraoperative NRT and EABR was useful for programming to prevent facial nerve stimulation. The patient, who was post-lingually deafened and diagnosed with advanced cochlear otosclerosis, received a cochlear implant in his left ear at the age of forty-five. Four years after the implantation he experienced facial nerve stimulation on his left face (implanted side) by use of the implant and he was not able to make full use of the electrode contacts due to facial spasm. As any modifications of programming did not help improving his word perception, he was referred to our Hospital at the age of sixty-seven. A preoperative computed tomography demonstrated otosclerosis involved the otic capsule and we diagnosed the right side with otosclerosis type 2c (double ring and narrowed basal turn) (Rotteveel et al., 2004). Pure tone audiogram showed he was totally deaf. After we obtained informed consent from the patient that cochlear implantation in otosclerosis would be technically demanding and would not be always satisfactory as it may elicit facial nerve stimulation, we implanted Cochlear® CI512 Contour Advance® electrode in his right ear. Facial nerve was stimulated by electrode contacts 10 -- 15 in intraoperative neural response telemetry (NRT), and by electrode contacts 11 -- 12 in intraoperative EABR monitoring. Two weeks after the operation we programmed his right cochlear implant by elevating current levels to the point where facial nerve would not be stimulated referring to the thresholds at which facial nerve was stimulated intraoperatively. He made full use of electrode contacts and his word recognition score increased from 15% preoperatively to 65% three months after implantation. In conclusion, intraoperative NRT and EABR monitoring was useful for mapping a cochlear implant to avoid potential facial nerve stimulation in advanced otosclerosis. [ABSTRACT FROM AUTHOR]