title: Changes of postoperative impedances in cochlear implant patients: the short-term effects of modified electrode surfaces and intracochlear corticosteroids.
abstract: OBJECTIVE
  The objective of this study was to investigate the effect of intraoperative application of steroid suspension and coating of the electrode contacts with a thin film of iridium oxide on the short-term, time-dependent development of the intracochlear impedance in adults implanted with the Nucleus 24 Contour electrode.
  
  
  METHODS
  The time-dependent development of intracochlear impedances was investigated in four different groups of adult patients at daily and later weekly intervals until the first fitting. The four groups were as follows: 1) standard Nucleus 24 Contour (control, n = 7); 2) standard Nucleus 24 Contour with intraoperative application of steroids (Group S, n = 6); 3) iridium-coated Nucleus 24 Contour control (Group I, n = 8); and 4) iridium-coated Nucleus 24 Contour with intraoperative application of steroids (Group I + S, n = 5). All patients had postlinguistic onset of severe to profound sensorineural hearing loss and no or little benefit of conventional hearing aids. Absence of ossification or any other cochlear anomaly and also absence of signs of retrocochlear or central origin to the hearing impairment bilaterally had to be confirmed preoperatively.
  
  
  RESULTS
  Steroid application reduced impedances significantly (Groups S and I + S), whereas iridium coating lowered variance of the impedance among patients but did not reduce the impedance significantly. The steroid-induced reduction is more pronounced at basal electrode contacts. Furthermore, there is some indication that the tissue growth could be faster in patients having the iridium-coated Contour electrode.
  
  
  CONCLUSIONS
  Provided that the reduction of electrode impedances with application of steroids is persisting, intracochlear application of steroids can be considered on a regular basis. Iridium coating of the electrode contacts seems not to be justified to be included as standard procedure.
authors.affiliation: Department of Otolaryngology, Medical University of Hannover, Hannover, Germany. Paasche.Gerrit@mh-hannover.de
authors.forename: Gerrit
authors.initials: G
authors.lastname: Paasche
authors.forename: Franziska
authors.initials: F
authors.lastname: Bockel
authors.forename: Claudia
authors.initials: C
authors.lastname: Tasche
authors.forename: Anke
authors.initials: A
authors.lastname: Lesinski-Schiedat
authors.forename: Thomas
authors.initials: T
authors.lastname: Lenarz
mesh_terms: D000305:Adrenal Cortex Hormones / Q000008:administration & dosage*; D000328:Adult; D000368:Aged; D003051:Cochlea / Q000187:drug effects*; D003054:Cochlear Implants; D003638:Deafness / Q000601:surgery*; D017097:Electric Impedance; D004567:Electrodes, Implanted; D005260:Female; D006801:Humans; D007430:Intraoperative Care; D007495:Iridium / Q000008:administration & dosage*; D008297:Male; D008875:Middle Aged; D011184:Postoperative Period; D011474:Prosthesis Design; D014057:Tomography, X-Ray Computed
chemical_list: D000305:Adrenal Cortex Hormones; C044458:iridium oxide; D007495:Iridium