Incomplete partition typeIII revisited-long-term results following cochlear implant.

Abstract

Incomplete partition typeIII (IPIII) is defined by amissing lamina cribrosa between the cochlea and the internal auditory canal (IAC). Cochlear implantation (CI) may result in an insertion of the electrode array into the IAC. The aim of this study is to evaluate CI surgery protocols, long-term audiological outcome, mapping and electrophysiological data after CI in IPIII patients. Nine IPIII patients were implanted with perimodiolar electrode arrays between 1999 and 2014; eight of them were included in this study. We evaluated mapping data, stapedius reflexes, electrode impedances and ECAP thresholds. We matched them with 3CI patients each with normal cochlear morphology regarding sex, age, side, implant type and surgical date. Speech discrimination was evaluated with the Oldenburger sentence test for adults, Göttingen audiometric speech test for children and the Freiburger monosyllabic word test. 3years after CI IPIII patients showed asignificant increase in pulse width, calculated electric load and electrode impedances in basal electrodes. Intraoperative electrically-evoked stapedius reflexes could be measured in all patients. Speech recognition scores were lower than average scores for matched patients, but without statistical significance. The significant increase of pulse width, electric load and electrode impedances of basal electrodes over time seem to be characteristic for IPIII patients probably occurring due to fibrosis and neurodegeneration of the cochlear nerve. The long term audiological results are stable. Intraoperative imaging and stapedius reflexes are highly recommended to control the right position of the electrode array.