Influence of the Insertion Depth of the Cochlear Implant Electrode on the Intra-Operative Electrophysiological Results in the Treatment with CI532 Implants
23 April 2019 (online)
Do the insertion depth of the electrode array with an attempt to optimize the perimodiolar position by the so-called pull-back technique (Basta et al., 2010) and the cochlea-close fixation method with the "Kiel knot" influence the intra-operative electrophysiological results in cochlear implant recipients?
In 31 post-lingual deaf adults with complete round-window insertion into the Scala tympani (without scale dislocation or tip fold-over) with a CI532 implant, the ECAP (electrically evoked compound action potential) thresholds at insertion depth of 1st marker, after array pull-back to the 3 rd marker as well as after fixation and CI electrode impedances were analysed intra-operatively, and compared with previous Kiel studies with CI512/CI RE (CA).
Statistically significant lower ECAP thresholds at the insertion depth marker ring 3 compared to marker 1 for the single electrodes E1 – 5, E8 and E10 – 12 (p < 0.05). In the basal electrodes E1 – 5 significantly higher ECAP thresholds compared to CI512/CI RE (CA). Apical lower electrode impedances in CI532 compared to CI512/CI RE (CA). There was no influence by the fixation method "Kiel Knot".
In comparison with results of CI512/CI RE (CA) (at middle marker), the CI532 electrode at insertion depth at 1. marker has basal higher ECAP thresholds which increase further after retraction to the 3 rd marker, so that the pull-back technique is not recommended. Further investigation will require whether there is an optimal CI insertion depth for the CI532, and whether withdrawing perimodiolar preformed CI electrodes have a positive impact on speech intelligibility with respect to electrophysiology.