The effect of pulling out cochlear implant electrodes on inner ear microstructures: a temporal bone study

Abstract

The exchange of an cochlear implant or the re-positioning of an electrode have become more frequently required than a decade ago. The consequences of such procedures at a microstructural level within the cochlea are not known. It was the aim of the present study to further investigate the effects of an CI electrode pull-out. Therefore 10 freshly harvested temporal bones (TB) were histologically evaluated after a cochlear implant electrode pull-out of a perimodiolar electrode. In additional 9 TB the intrascalar movements of the CI electrode while being pulled-out were digitally analysed by video- capturing. Histologically, a disruption of the modiolar wall or the spiral osseous lamina were not observed. In one TB, a basilar membrane lifting up was found, but it could not be undoubtedly attributed to the pull-out of the electrode. When analyzing the temporal sequence of the electrode movement during the pull-out, the electrode turned in one case so that the tip elevates the basilar membrane. The pull- out of perimodiolarly placed CI electrodes does not damage the modiolar wall at a microstructural level and should be guided (e.g., forceps) to prevent a 90 o turning of the electrode tip into the direction of the basilar membrane.

Figure 1

Scalaer overview. No sign of pull-out-related lesion.

Figure 2

BM lifting. Bubble formation with tissue shearing under the BM as a sign of BM lifting.

Figure 3

Exemplaric regular modiolar wall.

Figure 4

Cochlea with preperated basilar membrane before pull-out. CI array positioned under the BM.

Figure 5

Cochlea with preperated basilar membrane while pulling out. Regional reflex change of the basilar membrane with the array tip underneath as sign of a BM elevation.