Long-Term Evaluation of the Effect of Intracochlear Steroid Deposition on Electrode Impedance in Cochlear Implant Patients

Abstract

To evaluate the long-term effect of intracochlear steroid deposition on electrode impedance in patients with cochlear implants. A retrospective study was carried out comparing the impedances of cochlear implant electrodes with and without a single application of steroids in the cochlea. Ninety two implanted children with an average age of 5 years (range, 0.7 to 16 years) were divided in four groups according to the type of electrode and the use of steroids or not. In addition, the impedances of five children who required a reimplantation are reported. The impedances of Nucleus electrodes, either straight or Contour, were measured at regular intervals up to 12 months after surgery. Two months after surgery, the impedances in the steroid groups were significantly lower than in the nonsteroid groups (straight electrodes, 3.9 versus 4.7 kOhm, respectively; Contour electrodes, 5.4 versus 6.5 kOhm, respectively). This reduction remained stable over time for the straight electrodes, but for the Contour electrodes, it seemed to disappear after 6 months. The impedances after a second implantation were significantly higher than after a first implantation (median value, 8.8 kOhm after 2 months). The application of a single dose of a steroid solution reduces the electrode impedances significantly, and, for the straight electrodes, this effect seems to last. It seems justified to reimplant with caution, because this seems to increase the impedances substantially.