Revealing intracochlear microtrauma during cochlear implantation using optical coherence tomography and electrochemical sensing

Cochlear implants (CIs) are a highly effective treatment for severe to profound hearing loss, and earlier implantation is associated with improved auditory outcomes. As implantation is now extended to patients with residual hearing, preserving cochlear structures during surgery is a key priority. However, implant insertion trauma remains a risk and can compromise residual hearing. Currently, intraoperative methods capable of detecting such trauma in situ are lacking. We introduce a novel approach for in situ detection of intracochlear trauma using a gerbil model. Specifically, we use optical coherence tomography (OCT) in vivo to visualize structural damage, including basilar membrane ruptures and osseous spiral lamina fractures, and employ modified CI electrode arrays to sense hydrogen peroxide concentration, a marker of oxidative stress. Intracochlear trauma is validated and quantified using contrast-enhanced microcomputed tomography, enabling a novel trauma scale. Our results show that hydrogen peroxide levels are significantly correlated with the trauma scale and trauma volume. A receiver operating characteristic curve was established for the detection of intracochlear trauma, highlighting the sensor's diagnostic potential. These results show that combining in vivo OCT imaging with electrochemical sensing effectively detects intracochlear trauma, laying the foundation for next-generation CIs with real-time monitoring during implantation.