Effect of Return Electrode Placement at Apical Cochleostomy on Current Flow With a Cochlear Implant

Objectives: A method for stimulating the cochlear apex using perimodiolar electrode arrays is described. This method involves implanting an electrode (ECE1) into the helioctrema in addition to standard cochlear implant placement. One objective is to verify a suitable approach for implanting ECE1 in the helicotrema. Another is to determine how placement of ECE1 reshapes electric fields. Design: Two cadaveric half-heads were implanted, and electric voltage tomography was measured with ECE1 placed in many positions. Results: An approach for placing ECE1 was identified. Changes in electric fields were only observed when ECE1 was placed into the fluid in the helicotrema. When inside the helicotrema, electric voltage tomography modeling suggests an increased current flow toward the apex. Conclusions: Placement of ECE1 into the cochlear apex is clinically feasible and has the potential to reshape electric fields to stimulate regions of the cochlea more apical than those represented by the electrode array.