title: Evolution of impedance field telemetry after one day of activation in cochlear implant recipients.
abstract: Changes in impedance between 24 hours and one month after cochlear implantation have never been explored due to the inability to switch on within one day. This study examined the effect of early activation (within 24 hours) on the evolution of electrode impedance with the aim of providing information on the tissue-to-electrode interface when electrical stimulation was commenced one day post implantation.
  
  
  
  We performed a retrospective review at a single institution. Patients who received a Nucleus 24RECA implant system (Cochlear, Sydney, Australia) and underwent initial switch-on within 24 hours postoperatively were included. Impedance measurements were obtained intraoperatively and postoperatively at 1 day, 1 week, 4 weeks, and 8 weeks.
  
  
  
  A significant drop in impedance was noted 1 day after an initial activation within 24 hours followed by a significant rise in impedance in all channels until 1 week, after which the impedance behaved differently in different segments. Basal and mid-portion electrodes revealed a slight increase while apical electrodes showed a slight decrease in impedance from 1 week to 8 weeks postoperatively. Impedance was relatively stable 4 weeks after surgery.
  
  
  
  This is the first study to report the evolution of impedance in all channels between initial mapping 1 day and 1 month after cochlear implantation. The underlying mechanism for the differences in behavior between different segments of the electrode may be associated with the combined effect of dynamics among the interplay of cell cover formation, electrical stimulation, and fibrotic reaction.
authors.affiliation: Department of Otolaryngology, Cheng Hsin General Hospital, Taipei, Taiwan.|Institute of Clinical Medicine, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Hao-Chun
authors.initials: HC
authors.lastname: Hu
authors.affiliation: Cochlear Implant Center, Far Eastern Memorial Hospital, New Taipei, Taiwan.|Faculty of Medicine, School of Medicine, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Joshua Kuang-Chao
authors.initials: JK
authors.lastname: Chen
authors.affiliation: Department of Otolaryngology, Cheng Hsin General Hospital, Taipei, Taiwan.|Department of speech language pathology and audiology, National Taipei University of Nursing and Health Sciences, Taipei, Taiwan.
authors.forename: Chia-Mi
authors.initials: CM
authors.lastname: Tsai
authors.affiliation: Department of Otolaryngology, Lotung Poh-Ai Hospital, Yilan, Taiwan.
authors.forename: Hsing-Yi
authors.initials: HY
authors.lastname: Chen
authors.affiliation: Department of Medical Research and Education, Cheng Hsin General Hospital, Taipei, Taiwan.|Faculty of Public Health, School of Medicine, Fu-Jen Catholic University, Taipei, Taiwan.
authors.forename: Tao-Hsin
authors.initials: TH
authors.lastname: Tung
authors.affiliation: Department of Otolaryngology, Cheng Hsin General Hospital, Taipei, Taiwan.|Faculty of Medicine, School of Medicine, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Lieber Po-Hung
authors.initials: LP
authors.lastname: Li