A New Slim Modiolar Electrode Array for Cochlear Implantation: A Radiological and Histological Study.

Hypothesis: To explore the results of a new slim modiolar electrode array (SMA) with respect to intracochlear placement and trauma evaluated by detailed radiologic imaging and histology.

Background: Hearing and structure preservation is the goal of cochlear implantation for advanced hearing outcomes. Currently, this is most consistently achieved with thin lateral wall electrodes. Modiolar electrodes are located nearer the modiolus and may provide some electrophysiological advantages, but have a greater tendency for causing insertion trauma.

Methods: The SMA was implanted in 20 fresh-frozen human temporal bones (TB). All TBs were scanned pre- and postoperatively with cone beam computed tomography. For atraumatic insertion, the round window approach was preferred. Scalar localization and trauma were analyzed by three-dimensional image fusion reconstructions of the pre- and postimplant scans. The TBs underwent histologic examination to validate the radiologic findings.

Results: Insertion through the round window was performed in 19 TBs and through a cochleostomy in one TB. In one TB trauma in the form of scala translocation was identified radiologically and histologically. In the remaining TBs there was no insertion trauma. Adequate modiolar localization of the SMA was found in 19 of 20 TBs. The mean angular insertion depth was 400 degrees without correlation to cochlea size. There was no significant statistical difference between the radiological and histological measurements of electrode localization.

Conclusion: The SMA showed consistent and atraumatic insertion results in TBs. Pre- and postimplant cone beam computed tomography with image fusion was shown to be very accurate for the assessment of electrode position and insertion trauma.