Intraoperative Measured Electrocochleography and Fluoroscopy Video to Detect Cochlea Trauma.

HYPOTHESIS: Gross electrode movements detected with intraoperative, real-time X-ray fluoroscopy will correlate with fluctuations in cochlear output, as measured with intraoperative electrocochleography (ECochG). BACKGROUND: Indications for cochlear implantation (CI) are expanding to include patients with residual hearing; however, implant recipients often lose residual hearing after CI. The objective of this study was to identify probable traumatic events during implantation by combining electrophysiological monitoring of cochlear function with simultaneous X-ray monitoring. The surgical timing of these apparently traumatic events was then investigated. METHODS: For 19 adult patients (21 surgeries, 2 bilateral), the ECochG responses were measured during implantation of a cochlear nucleus slim modiolar electrode (CI532/CI632, Cochlear Ltd Australia Nucleus slim modiolar). Simultaneous fluoroscopy was performed, as well as a postoperative cone-beam computed tomography (CT) scan. For all patients, pre- and postoperative audiograms were recorded up to 1 year after surgery to record the loss of residual hearing. RESULTS: Electrode insertions for 21 surgeries were successfully monitored. A drop in ECochG response was significantly correlated with reduced hearing preservation compared with patients with preserved responses throughout. Drops in the ECochG response were measured to occur during insertion, because of movement of the array after insertion was complete, including while sealing of the electrode array at the round window or coiling of the array lead within the mastoid cavity. In some patients, a reduction in cochlear output, resulting in poor ECochG response, was inferred to occur before the beginning of implantation. CONCLUSION: The combination of perioperative ECochG measurements, microscope video, fluoroscopy, and postoperative CT scan may inform on what causes the loss of residual hearing after implantation. These findings will be used to improve the surgical procedure in future.

Effect of Proximity to the Modiolus for the Cochlear CI532 Slim Modiolar Electrode Array on Evoked Compound Action Potentials and Programming Levels.

BACKGROUND: The first surgeries with CI532 showed an effect of the proximity of the electrode to the modiolus on the Evoked Compound Action Potentials (ECAPs). OBJECTIVES: Objectives of the study were to investigate the effect of the "pullback" procedure on intraoperative ECAP responses in three different electrode array positions and additionally to compare behavioral thresholds with the thresholds obtained in a group of patients using the standard insertion. The hypothesis of this study is that pullback will cause lower ECAPs and behavioral thresholds. PATIENTS: The study included 40 patients, 20 in the pullback insertion group and 20 in the standard insertion group (without pullback). METHOD: During insertion of the CI532 electrode array, ECAP was performed in three different positions for the pullback group: at initial insertion, at over-insertion, and after pullback. Insertion was monitored by fluoroscopy. In the standard group, ECAP was performed at the initial position, which is also the final position. ECAP thresholds (T-ECAPs) were compared within subjects at the initial and the final position in the pullback group and between groups in the final positions of the pullback and standard groups. Programming levels (C- and T-levels) were compared between the two groups 1 year after switch-on. RESULTS: Intraoperative measurements pullback shows lower average T-ECAPs after pullback compared to thresholds in initial position. Comparison of intraoperative T-ECAPs at the final positions showed no statistically significant difference between the pullback group and the standard insertion group. Furthermore, 1 year after switch-on there was no statistically significant difference in C- and T-levels between the two groups. CONCLUSION: The pullback maneuver of the CI532 electrode array after an over-insertion gave significantly lower T-ECAPs compared to the thresholds at the initial position. However, the between-groups analysis of pullback and standard insertion showed neither significantly different T-ECAPs nor different programming levels. Because T-ECAPs and programming levels vary considerably between subjects, large groups are required to detect differences between groups. Additionally, the effect pullback technique to preserving the residual hearing is not known yet.

Fusion of Technology in Cochlear Implantation Surgery: Investigation of Fluoroscopically Assisted Robotic Electrode Insertion.

The HEARO cochlear implantation surgery aims to replace the conventional wide mastoidectomy approach with a minimally invasive direct cochlear access. The main advantage of the HEARO access would be that the trajectory accommodates the optimal and individualized insertion parameters such as type of cochlear access and trajectory angles into the cochlea. To investigate the quality of electrode insertion with the HEARO procedure, the insertion process was inspected under fluoroscopy in 16 human cadaver temporal bones. Prior to the insertion, the robotic middle and inner ear access were performed through the HEARO procedures. The status of the insertion was analyzed on the post-operative image with Siemens Artis Pheno (Siemens AG, Munich, Germany). The completion of the full HEARO procedure, including the robotic inner ear access and fluoroscopy electrode insertion, was possible in all 16 cases. It was possible to insert the electrode in all 16 cases through the drilled tunnel. However, one case in which the full cochlea was not visible on the post-operative image for analysis was excluded. The post-operative analysis of the electrode insertion showed an average insertion angle of 507°, which is equivalent to 1.4 turns of the cochlea, and minimal and maximal insertion angles were recorded as 373° (1 cochlear turn) and 645° (1.8 cochlear turn), respectively. The fluoroscopy inspection indicated no sign of complications during the insertion.