Impedance development after implantation of coated CI electrodes in guinea pigs

Impedance is the complex resistance at the electrode contacts of a cochlear implant (CI) electrode when stimulating the hearing nerve electrically. It comprises the access resistance and a polarization part. In clinical routine, typically only one value is measured and it is not discriminated between the different parts of the impedance. When investigating coated CI electrodes in guinea pigs, we had the possibility to do additional measurements and therefore to distinguish between access and polarization parts of the impedance. By this, it was possible to investigate both over time to follow their development after implantation when fibrous tissue is growing. Four groups of animals with N=6 each were formed: Control, PLLA coated, PLLA with diclofenac and PLLA with MM284-loading. Impedances were measured daily for the first 2 weeks and then weekly until 4 weeks after implantation. Impedances increase after implantation but the increase was delayed in the groups with drugs loaded into the coating. An increase was observed for both parts of the complex impedance. The results support earlier observations in our lab and rebut the view of other researchers that growth of fibrous tissue after cochlear implantation only affects the access part of the impedance.

BMBF RESPONSE 03ZZ0933H

Publication History

Article published online:
12 May 2023