Residual hearing in cochlea implant patients with CI532 electrode from Cochlear®
23 April 2019 (online)
Patients with cochlea implants benefit from a functional residual hearing particularly in complex hearing situation (i.e. noise). The modiolus-close CI532 electrode shall allow for an improved residual hearing due to its thin and flexible structure.
37 CI532 patients (> 18 years) were divided into 2 groups prior to surgery: 1. Patients with residual hearing (RH, n = 14) 2. without (noRH, n = 23). Residual hearing was defined the following criteria: a. bone conduction of < 85 dB in frequencies of 125, 500, 1000, 2000 in pure tone audiogram and/or less than 60 dB hearing loss of digits or c. > 50% monosyllables maximum in Freiburger speech test. Hearing tests were assessed preoperatively and within the regular check-ups (1day, 3 months, 6 months, 12 months postOP). In addition, NRT data was collected intra- and postoperatively. 3D C-arm was used to check the correct position of the electrode in parallel CI522 patients were assessed (RH522, n = 16).
After implantation we observed a continuous decrease in RH (1 day postOP 7/13 patients with RH (54%), 3 months postOP 2/8 (25%), 6 months postop 1/9 (11%),12 months postOP 0/8 (0%). Interestingly low frequencies tended to be lost more easily. Two tip fold-over were recognized by 3D C-arm scans. CI522 RH patients had a better outcome compared to CI532.
So far there is no evidence for long term residual hearing preservation, but still it cannot be totally excluded. One reason could be the trauma caused by an exoskelett used by insertion of the electrode or a progress of the natural hearing loss.