Influence of the Insertion Depth of the Cochlear Implant Electrode on the Intra-Operative Electrophysiological Results in the Treatment with CI532 Implants

Introduction:

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?

Methods:

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).

Results:

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".

Conclusions:

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.

Publication History

Publication Date:
23 April 2019 (online)