Introduction: Cochlear implantation allows the rehabilitation of profound bilateral
deafness, restoring speech perception and verbal communication when the traditional
hearing aid no longer provides satisfactory hearing gain.
A cochlear implant includes an electrode array and its functioning is based on the
principle of cochlear tonotopy: Each electrode encodes a frequency spectrum according to
its position in the cochlea (high frequencies are assigned to the basal electrodes and
low frequencies to the apical electrodes). The cochlear implant thus breaks down the
frequency spectrum into a number of frequency bands via bandpass filters corresponding to
the number of electrodes in the implant. During the fitting these bands can be modified
by the audiologist.
MED-EL has developed a fitting strategy (ABF) that allows, from a post-operative scanner,
to calculate the theoretical characteristic frequency of neurons stimulated by each
electrode contact and to transmit this information to the fitting software of the CI.
Bimodal hearing refers to the use of a CI in one ear with a HA on the contralateral side.
This association allows for adults and children a better perception of speech in quiet
and in noise, a better perception of music, hearing comfort, better sound quality, better
localization of sound and, consequently, a better quality of life compared to unilateral
CI alone. However, there is great variability in the integration process; while some
bimodal users show substantial benefits, others receive little or no benefit.
This variability could be due to different processing times between CI and contralateral
HA.
Recently, MED-EL (Austria) has developed a new approach to synchronize the treatment time
of the CI with that of the contralateral HA via the fitting software. This new approach
takes into account the different treatment times between CI and contralateral HA and
allows synchronization between the 2 systems (CI and HA).
This strategy (ABFS) could therefore allow a better integration of information in bimodal
hearing and in particular improve the sound localization compare to a strategy without
synchronization (ABFnoS).
Main objective:
For a bimodal fitting (hearing aid (HA) + cochlear implant (CI)): Comparison of a
tonotopy based fitting strategy with synchronization between HA and CI (ABFS) to a
tonotopy based fitting strategy without synchronization (ABFnoS) for the accuracy of
sound localization.
Secondary objectives:
Comparison of ABFS to ABFnoS for the bias of sound localization. Comparison of ABFS to
ABFnoS for speech perception in noise. Comparison of ABFS to ABFnoS for the auditory
skills experienced by the subject.
Plan of the study:
It is a prospective open monocentric randomized crossover study: Measures will be done on
the patient at 6 weeks and 12 weeks post-activation.
