Protocol for CHIEF (cochlear implants and inner ear inflammation) study; an observational, cross-sectional study of children and young people undergoing cochlear implantation.

<ns3:p>Introduction Cochlear implantation is a surgical intervention for people with severe-to-profound hearing loss. Electrodes in the cochlea generate electrical currents that stimulate the auditory nerve to elicit hearing. Despite the success of cochlear implants, some people do not receive the expected hearing benefits. One reason for this is that tissues in the cochlea vary in their response to implantation of the electrode array. Many people have a healthy wound-healing response that results in mature scar tissue (fibrosis). However, some individuals have a heightened inflammatory response associated with excessive fibrosis. This leads to greater electrical resistance to the current flow (impedance) and reduces the quality of electrical stimulation, both of which can lead to poorer hearing outcomes with the implant. Excessive inflammation can damage cochlear structures and result in loss of residual hearing. This study will increase our understanding of why some people have a heightened inflammatory response that leads to poorer hearing. We propose that there are detectable individual inflammatory differences between people when they are implanted, which may result in variable hearing outcomes following implantation. If we could understand and identify these differences, we could detect people who may be at risk of less favorable outcomes and use therapies to modulate inflammation and improve outcomes. Methods and analysis A cross-sectional study of children and young people undergoing cochlear implantation. On the day of surgery, a middle ear mucosa sample, swabs of the nasopharynx and middle ear, cochlear fluid, and blood samples will be collected. Samples will be analyzed using molecular techniques to determine the inflammatory status of the person at the time of implantation. Clinical hearing data will be collected for up to five years after implantation to explore the relationship between inflammation at the time of implantation and long-term hearing outcomes.</ns3:p>