gms | German Medical Science

Introduction: The performance in cochlear implant users depend on 4 important factors: 1- The electrode technology, 2- the speech processing strategies, 3- the number of the surviving spiral ganglion cells and auditory nerve fibers and 4- Brain plasticity. In this study we will show the effect of improvements in electrode technology and speech processing strategies on the performance of a cohort of more than 1000 postlingually deafened adult Cochlear implant subjects implanted in Hannover. In addition we will observe the long term performance up to 24 years after implantation and the effects of gender and old age on the hearing performance with CI.

Material and methods: This is a longitudinal retrospective cohort study on 1005 postlingually deafened adult subjects who were implanted from July 1984 till Jan 2008 in ENT department of the Medical University of Hannover. All the subjects spoke German as native language and were traditional CI candidates. Subjects with additional handicaps, cochlear ossification and inner ear malformations were excluded from this study. The results of up to 24 years of follow up are presented in Freiburger Monosylabic Test, Speech Tracking and HSM sentence test in quiet and in 10dB noise.

Results and conclusion: Technological improvements in the past 24 years have lead to a significant improvement in the hearing performance of the different groups of subjects in this large cohort of postlingually deafened CI patients, there is no significant difference in performance between the genders and no significant deterioration of the results in the geriatric group. The stability of the results over a period of 24 years is an evidence to the safety and reliability of cochlear implantation for hearing restoration in deaf patients.