title: Electron microscopy changes of cochlear implant electrodes with permanently high impedances.
abstract: OBJECTIVE
  Impedance measurements by means of telemetry have provided us with an objective test of cochlear implant function. Unmeasurable impedance suggests a possible defect on the corresponding channel of the electrode. However, increasing impedances could suggest inflammatory  and/or proliferating processes along the electrode. In this report we examined correlations between high impedance, measured in vivo and in vitro findings on the electrode surfaces.
  
  
  METHODS
  We describe recurrent increases in cochlear implant electrode impedance  in the same channels, which could initially be reversed by reprogramming the implant, and with anti-inflammatory treatment using cortisone and antibiotics. Subsequently, however, the impedances remained consistently high, indicating a cochlear implant defect. After the removal of the cochlear  implant, the electrodes were examined using light and scanning electron microscopy.
  
  
  RESULTS
  Examination of the electrodes with normal impedance values revealed, in the great majority of the electrodes, silver shining surfaces. On the other hand, electrodes with high impedances  were found coated with tissue. Further analysis of these electrodes using scanning electron microscopy also demonstrated surface changes.
  
  
  CONCLUSIONS
  Persistently high impedances were related to changes on the electrodes' surface and to coating with tissue in this case.  These changes can result in adhesive processes and technical malfunction, leading to explantation and difficult re-implantation. Therefore, close and professional supervision of cochlear implant patients is needed.
authors.affiliation: Department of Otorhinolaryngology,Medical University of Hanover, Hanover, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Durisin
authors.forename: Christian
authors.initials: C
authors.lastname: Krause
authors.forename: Christoph
authors.initials: C
authors.lastname: Arnoldner
authors.forename: Georgios
authors.initials: G
authors.lastname: Kontorinis
authors.forename: Andreas
authors.initials: A
authors.lastname: Buechner
authors.forename: Thomas
authors.initials: T
authors.lastname: Lenarz
authors.forename: Anke
authors.initials: A
authors.lastname: Lesinki-Schiedat
authors.forename: Oliver
authors.initials: O
authors.lastname: Profant
authors.forename: Juergen
authors.initials: J
authors.lastname: Neuburger
mesh_terms: D003054:Cochlear Implants; D017097:Electric Impedance; D006801:Humans; D007223:Infant; D008297:Male; D008855:Microscopy, Electron, Scanning; D011475:Prosthesis Failure; D013686:Telemetry