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International audience; ISSUE : Cochlear implant is for people with severe to profound sensorineural hearing loss. Currently, the most difficult task during implant surgery is inserting the electrode array properly into the tympanic ramp of the patient's cochlea. Problem solving: New prototype with low stiffness and with on electronically conductive polymer (ECP) based micro-actuators to reduce friction forces allows better control of insertion process, facilitate the work of surgeon and decrease the probability of trauma.

Cochlear implants are the most successful neuro-prostheses. They restore hearing by replacing the function of damaged sensory cells inside the cochlea. Direct stimulation of the auditory nerve is driven through current generated at electrodes inserted into the cochlea. Despite the success of cochlear implants some individuals underperform or fail i.e. do not achieve the anticipated benefits. A significant proportion of the failures are not due to hardware or surgical factors but are likely partly due to the biological response at the electrode-tissue interface. As availability of human tissue to investigate the tissue response to cochlear implantation is limited, there is great need for effective in vivo models. We are establishing a mouse model to investigate the response at the electrode-tissue interface with the aim of understanding how the response to the implant may alter hearing performance, and how this is altered by different cochlear implants. As part of the characterisation of the model, µCT will be used to provide 3D structural information about the cochlea pre-implantation. Optimally designed, functional, electrode arrays will be surgically implanted into mice through the round window of the cochlea. µCT scans will be captured as a method to validate surgical technique and identify tissue damage caused by electrode insertion. The aim is to corroborate the 3D structural information with detailed cellular information from post-mortem histological analysis to gain further understanding in the biological response at the electrode-tissue interface in the rodent model. Preliminary work determined the µCT resolution possible of a decalcified wax-embedded cochlea. Highly informative, high resolution images were obtained as shown below. Morphological information from the digital cochlea µCT sections will now be compared with tissue morphology and cellular expression information obtained from immunostaining. Pairing high resolution, µCT images of the mouse cochlea post-implantation with in-depth histological analysis of the tissue will advance understanding of the biological response at the CI-tissue interface.