title: The long-term effects of modified electrode surfaces and intracochlear corticosteroids on postoperative impedances in cochlear implant patients.
abstract: OBJECTIVE
  The objective of this study was to investigate the long-term effect of intraoperative application of steroid suspension and coating of the electrode contacts with a thin film of iridium oxide on the intracochlear impedance development after cochlear implantation and on the impedance difference before and after stimulation.
  
  
  METHODS
  Time-dependent development of intracochlear impedances was investigated in 4 different groups of adult patients up to 4 years after implantation. Additionally, during rehabilitation period just after first fitting, impedances before and after stimulation were measured as to investigate the influence of electrical stimulation on the impedances. Results from standard Nucleus 24 Contour (control), standard Nucleus 24 Contour with intraoperative application of steroids, iridium-coated Nucleus 24 Contour, and iridium-coated Nucleus 24 Contour with intraoperative application of steroids were compared.
  
  
  RESULTS
  Steroid application reduced impedances significantly throughout the observation period of up to 4 years after implantation. Iridium oxide coating had no effect. Differences between the groups were mainly found on the basal and middle parts of the cochlea, but not close to the tip of the array, also indicating that postoperative fibrous tissue growth is stronger in the basal region of the cochlea. Group mean values of the stimulation effect were not influenced by the different treatments. Nevertheless, only in both steroid-treated groups a correlation between the impedance before stimulation and the stimulation effect was found.
  
  
  CONCLUSIONS
  Although the differences between control and steroid-treated groups decrease with time, single intraoperative intracochlear steroid deposition was proven to lower postoperative impedances during first 3 to 4 years after implantation probably because of reduction of fibrous tissue growth.
authors: Department of Otolaryngology, Medical University of Hannover, Hannover, Germany. Paasche.Gerrit@mh-hannover.de
authors: Gerrit
authors: G
authors: Paasche
authors: Claudia
authors: C
authors: Tasche
authors: Timo
authors: T
authors: Stöver
authors: Anke
authors: A
authors: Lesinski-Schiedat
authors: Thomas
authors: T
authors: Lenarz
mesh_terms: D000158:Acoustic Impedance Tests; D000305:Adrenal Cortex Hormones / Q000008:administration & dosage / Q000494:pharmacology*; D000328:Adult; D000368:Aged; D003051:Cochlea / Q000502:physiology*; D019929:Cochlear Implantation; D003054:Cochlear Implants; D003627:Data Interpretation, Statistical; D004558:Electric Stimulation; D004566:Electrodes; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007267:Injections; D008297:Male; D008875:Middle Aged
chemical_list: D000305:Adrenal Cortex Hormones