Fibrosis tissue growth after the CI is an inflammatory reaction to a foreign body
occurring around the electrode array. It is considered responsible for a larger current
diffusion, less precise stimulation of auditory nerve fibres and elevated electrical
impedances thus affecting the functioning and the battery life of an implant. Fibrosis
has been also proposed as a factor reducing residual hearing. Hence, its early detection
and prevention can significantly improve the outcomes of CI.
To date, no reliable technique to visualise cochlear fibrosis in vivo exists. However,
the TIM measurement developed by Cochlear® including depth sounding and spectroscopy
tools could possibly provide a better "view" of the fibrosis apparition after CI. This
approach has been already successfully applied in the University Hospital of Montpellier,
France, to the patients-users of the Advanced Bionics cochlear implants.
One of the factors provoking the fibrosis tissue development is an electrode positioning
into the scala vestibule (SV) versus scala tympani (ST). CBCT will be used to visualise
the electrode location as well as possible damages of the inner ear caused by CI. The
imaging data will be then linked to the TIM measurements results.
Potential participants will be recruited from the French population of the Cochlear®
implant users either coming for their regular checks-up at the ENT service of the
University Hospital of Montpellier and implanted for more than 6 month (time necessary
for the fibrosis tissue to develop) or recently implanted at the same hospital.
For the patients with long-term implantation (160 participants planned) the TIM
measurements will be performed only once whereas the newly implanted group (20
participants planned) will require these measurements to be repeated several times: on
the day of the surgery as well as 15 days, 1 month, 2 months, 3 months and 6 months after
it. For the first group the post operational CBCT imaging file will be extracted from the
patient medical record; for the second group CBCT will be performed during the surgery.
The main objective of this study is:
For the group with long-term implantation - to show the difference in TIM profiles
according to the electrode scala position (ST or SV) determined by CBCT 6 months or more
after the implantation For the group with recent implantation - to evaluate the changes
in TIM profiles with time according to the electrode scala position (ST or SV) determined
by CBCT
The secondary objectives are common for both groups:
To analyse various patient subgroups defined by the electrode type (Contour Advanced
- only for long-term implantation, Slim Straight, Slim Modiolar) and the inner ear
access (round window, enlarged round window or cochleostomy)
To identify the TIM profile threshold values, potential indicators of the cochlear
fibrosis apparition, depending on the electrode type
To evaluate the depth sounding tool accuracy for the measurement of the distance
between the electrode and the spiral ganglion in comparison to CBCT depending on the
type of the electrode array.
To evaluate the spectroscopy tool accuracy for fibrosis detection in specific
cochlear areas (around electrodes dislocated to SV or basal electrodes in case of
cohleostomy)