Concentration-dependent transient reduction of impedances by intracochlear steroid injections with a cochlear catheter
23 April 2019 (online)
Steroids can reduce foreign body reaction and excessive scarring. The extent of connective tissue growth around the cochlear implant (CI) electrode correlates with the postoperatively measurable impedances. In previous studies, it was possible to achieve a concentration-dependent lowering of the impedances by intracochlear triamcinolone injection using a specially designed cochlear catheter also in apical areas of the cochlea. In order to evaluate the sustainability of this effect, the patients were tracked accordingly and long-term data were evaluated.
Materials and Methods:
5 patients without functional residual hearing with triamcinolone (low dose: 4 mg/ml vs. high dose: 20 mg/ml) were treated with a cochlear catheter before implantation with a Med-El Flex 28 electrode. Impedances and Electrically Evoked Compound Action Potentials as well as the Amplitude Growth Function were measured at defined times and compared with a control group with the same electrode, similar residual hearing but without catheter application.
Undesirable effects were not recorded. While in the low dose group the impedances decreased only in the first weeks compared to the control group, the effect in the high dose group was detectable both basal and apical until after first fit. In all subsequent measurements thereafter, there were no significant differences between the groups. Functional results were also comparable.
Deep intracochlear administration of triamcinolone with a cochlear catheter provides a concentration-dependent, transient decrease in impedance. This effect was detectable even at high doses only until after first fit.