Comparison of electrode position in the human cochlea using various perimodiolar electrode arrays

Objective: This study was conducted to evaluate the insertion properties an d intracochlear trajectories of three perimodiolar electrode array designs and to compare these designs with the standard Cochlear/Melbourne array. Background: Advantages to be expected of a perimodiolar electrode array inc lude both a reduction in stimulus thresholds and an increase in dynamic ran ge, resulting in a more localized stimulation pattern of the spiral ganglio n cells, reduced power consumption, and, therefore, longer speech processor battery Life. Methods: The test arrays were implanted into human temporal bones. Image an alysis was performed on a radiograph taken after the insertion. The cochlea s were then histologically processed with the electrode array in situ, and the resulting sections were subsequently assessed fur position of the elect rode array as well as insertion-related intracochlear damage. Results: All perimodiolar electrode arrays were inserted deeper and showed trajectories that were generally closer to the modiolus compared with the s tandard electrode array. However, although the precurved array designs did not show significant insertion trauma, the method of insertion needed impro vement. After insertion of the straight electrode array with positioner, si gns of severe insertion trauma in the majority of implanted cochleas were f ound. Conclusions: Although it was possible to position the electrode arrays clos e to the modiolus, none of the three perimodiolar designs investigated fulf illed satisfactorily all three criteria of being easy, safe, and atraumatic to implant.