Preliminary Results With Image-guided Cochlear Implant Insertion Techniques.

HYPOTHESIS

Using patient-customized cochlear measurements obtained from preoperative computed tomography (CT) scans to guide insertion of cochlear implant (CI) electrode arrays will lead to more optimal intracochlear positioning.

BACKGROUND

Cochlear duct length is highly variable ranging from 25.26 to 35.46 mm, yet CI electrode arrays are treated as one size fits most. We sought to investigate the impact of patient-customized insertion plans on final location of electrode arrays.

METHODS

Twenty cadaveric temporal bone specimens were CT scanned and randomly divided into groups A and B. Group A specimens had an optimal customized insertion plan generated including entry site (e.g., round window versus extended round window), entry vector based on anatomical landmarks (e.g., hug posterior aspect of facial recess and angle 1 mm inferior to stapes), depth to begin advancing off stylet, and final insertion depth. Suboptimal plans were chosen for group B by selecting an approach that was normal yet predicted to result in poor final electrode location. One surgeon, blinded as to group, carried out the CI insertions following which the electrode array was fixed using superglue and the specimen CT scanned to allow assessment of final electrode location.

RESULTS

Average perimodiolar distances for groups A and B were 0.51 and 0.60 mm, respectively. For group A, full scala tympani insertion was achieved in all specimens while in group B, 4 of 10 specimens had scalar translocation.

CONCLUSION

Patient customized cochlear implant insertion techniques achieved better positioning of electrode arrays in this study and have potential for improving electrode positioning in patients.