Intracochlear position of cochlear implant electrodes

The insertion of cochlear implant electrodes in human temporal bones may be associated with the destruction of structures within the cochlea. The aim of this study was to measure such insertional trauma by means of histologic processing of implanted human temporal bones following implantation of a C ombi 40/40+ electrode array (Med-El, Innsbruck). We implanted 6 human tempo ral bones with original electrodes (3 with Combi 40 and 3 with Combi 40+). In 4 bones Healon was used for electrode insertion. The histological invest igation was performed after radiographic evaluation of the position of the electrode. For the histological procedure we used a technique which keeps t he electrodes in position within the cochlea. In these slides we could clea rly identify the electrodes in the tympanic scale. When inserted properly ( point of first resistance) no trauma occurred in the basal portion of the c ochlea and minimal trauma in the middle portion of the cochlea.