Corroborating µCT and histological data to provide novel insight into the biological response to cochlear implantation at the electrode-tissue interface

Cochlear implants are the most successful neuro-prostheses. They restore hearing by replacing the function of damaged sensory cells inside the cochlea (hearing part of the inner ear). 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 may also be 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 have established 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 materials coating the array. Optimally designed, functional, electrode arrays have been surgically implanted into mice through the round window of the cochlea. µCT imaging and visualisation has been used to obtain 3D structural information about the cochlea pre-implantation and to visualise the position of array to validate surgical technique post-implantation. Further work will involve implanting and recovering the mice then µCT imaging immediately after culling to visualise any soft tissue damage caused by electrode insertion. The overall aim is to corroborate high resolution µCT images of the mouse cochlea post-implantation with in-depth histological analysis of the tissue to provide essential insight into the biological response at the CI-tissue interface.