Assessment of intracochlear electrode position and correlation with behavioural thresholds in CII and 90K cochlear implants

Conclusion. The image quality of 64-MDCT provided excellent definition of the fine osseous structures and individual electrode contacts. Evaluation of electrode distances revealed a more focused stimulation for the Helix contacts, with better optimization of pulse width and frequency of stimulation. Objectives. A multi-slice CT scan was performed postoperatively to evaluate electrode distance from the modiolus and variability of fitting parameters ( M level) for two different types of cochlear implant electrode carriers, CII and 90K implants with 1J and Helix electrode carriers. Materials and methods. The electrode's position in different cochlear implant (CI) electrodes, Advanced Bionics 90K 1J and Helix, was assessed postoperatively in 20 adult patients by means of a 64-MDCT scanner. Axial, coronal, and oblique 0.3 mm multiplanar reconstructions ( MPRs) were obtained and datasets were analyzed to assess the intracochlear position and distance from the surface of the electrodes to the bony edge of the modiolus. Patients' fitting characteristics were gathered at the time the CT was performed and correlated to intracochlear measurements. Results. Determination of contact distances confirmed smaller average values for the Helix at the apex and medial segments. Helix electrodes were closer to the modiolus in all segments. Likewise, M level determination showed lower values for the Helix carrier, confirming a more focused stimulation and better optimization of pulse width and frequency of stimulation.