Cochlear implantation with the nucleus slim modiolar electrode (CI532): a preliminary experience

To combine the benefits of perimodiolar stimulation with minimal insertion trauma, a thin, pre-curved electrode (CI532) was recently developed by Cochlear Ltd. (Sidney). This array is held straight prior to insertion by an external polymer reloadable sheath that is removed after full electrode insertion. Sixty-seven patients suffering from severe-to-profound sensorineural hearing loss (mean age 42.2 years; mean duration of the hearing loss 19.6 years; mean PTA thresholds at 250-2000 Hz 92.4 dB HL) were implanted with the CI532. Mean duration of surgery was 58.7 min. In 61 patients, a round window (RW) approach was used. In the remaining six cases, a cochleostomy was done because of RW ossification. Impedances and NRT for each electrode are reported. NRT ratio average value was 0.86 +/- 0.12 predicting correct scala tympani electrode placement. Post-operative PTA threshold in the implanted ear was 102.9 dB HL. Finally, speech recognition level in quiet at 65 dB HL was 44.6%, after a short follow-up (mean 5.2 months). Our preliminary experience with the new CI532 shows good surgical, electrophysiological, and audiological outcomes. In particular, our results are promising regarding the possibility to achieve minimal insertion trauma and good residual hearing preservation with the use of a deep inserted close modiolar electrode.