Simpler and effective radiological evaluations for modiolar proximity of a slim modiolar cochlear implant electrode

Abstract

A new slim modiolar electrode (CI532/632) has been reported to ensure better modiolar proximity than conventional electrodes. Better modiolar proximity has been proposed to yield better electrode discrimination capability and potentially better speech outcomes, necessitating its efficient measurement. Currently, intracochlear positional index (ICPI), the most reliable indicator for evaluating modiolar proximity, has been measured exclusively through ‘metal artifact-less’ cone beam CT. However, popular use of this index is precluded due to lack of cone beam CT in many institutions. Thus, eyes are now on elucidation of easy-to-measure indicators of modiolar proximity derived from conventional CT, which is accessible in all centers. We observed that enhanced tomographic resolution significantly reduces partial volume artifacts, providing better visualization of modiolus-electrode distance. Aided by ultra-high kernel specification with high-resolution index, we developed a novel and easy-to-measure, conventional CT-specific indicator, “modified ICPI”, for evaluation of modiolar proximity. Further, we showed that it closely correlates with the previously proposed parameter of modiolar proximity, the spiral diameter, measured from post-insertion radiograph, reiterating the value of X-ray-based spiral diameter. Through this study, we have taken a step toward the stage of immediate visual feedback regarding modiolar proximity and changes in insertion technique intraoperatively, ensuring optimal modiolar proximity.

Potential Implications of Slim Modiolar Electrodes for Severely Malformed Cochleae: A Comparison With the Straight Array With Circumferential Electrodes

“…The electrically evoked compound action potential (ECAP) response is largely associated with SGNs [ 12 ]. Further, it has been proven that the electrode-modiolus distance is closely correlated with the ECAP thresholds of electrodes, including slim modiolar electrodes [ 13 ]. Thus, it is now possible to see immediate feedback of the electrode position with the neural structure.…”

Hearing Features and Cochlear Implantation Outcomes in Patients With PathogenicMYO15AVariants: a Multicenter Observational Study

“…This is beneficial to patients at risk of progressive hearing loss (Yoshimura et al 2020). Additionally, recent studies have also proposed that slim modiolar electrodes can be used to achieve comparable hearing preservation as that achieved by using slim straight electrodes in patients with significant low-frequency hearing loss (Ramos-Macías et al 2017; Durakovic et al 2020; Lee et al 2020). The use of a slim electrode with sufficient length, whether of straight or of modiolar type, is recommended for MYO15A -related SNHI or other genetic SNHI with similar audiological features.…”

Two Discrete Types of Tip Fold-Over in Cochlear Implantation Using Slim Modiolar Electrodes: Influence of Cochlear Duct Length on Tip Fold-Over

“…All patients underwent intraoperative x-ray scans in the operating room to verify the final placement of the electrode tip, as recommended (13). If the initial x-ray showed tip fold-over of the electrode, the electrode was retracted, reloaded, and reinserted until the array was confirmed to be optimal in the final x-ray image.…”