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A digital model of the cochlea gives hope to patients with severe deafness

Three teams located on the Côte d'Azur formed a research partnership with the aim of increasing knowledge on the anatomy of the cochlea, the part of the inner ear involved in transmitting sounds. The fruit of this collaboration between the Inria, the Nice University Hospital Center/Université Côte d'Azur and Oticon Medical was a reconstructed 3D model of the cochlea that was used for the first time in cochlear implant surgery.

Publication : 03/07/2019
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Thanks to a partnership between the Nice University Hospital Center, Inria and Oticon Medical, patients suffering from severe deafness who can no longer benefit from conventional hearing aids, find new hope of having their hearing restored with better modeling of their cochlear anatomy. This technological advance was instrumental in the development of a customized hearing implant that sends an electrical stimuli directly to the auditory nerve. The first two implants were placed in two patients of Dr. Nicolas Guevara, ENT surgeon at the Nice University Hospital Center in May. The implants were successfully activated on June 7 at the Face and Neck Institute in the presence of the CHU, Inria and Oticon Medical teams.

The cochlea, a complex structure related to sensorineural deafness

The cochlea is a small structure of the inner ear that transforms sound vibrations into electrical signals and transmits them to the auditory nerve. This transmission is defective in individuals with severe sensorineural hearing loss, who are thus candidates for cochlear implants. The operation involves implanting a medical device that captures sounds, transforms them into an electrical signal, and transmits them to the auditory nerve via electrodes inserted into the cochlea. The three-dimensional structure of the cochlea is complex and spiral-shaped. Because of its small size, the preoperative MRI scan cannot render an accurate image. The research partnership's goal was to develop a mathematical 3D cochlear model from these low-resolution scans, and provide the medical teams performing cochlear implants with better anatomical information.

Modeling the cochlea in three dimensions

The model was developed by Thomas Demarcy as part of his thesis research. He is a member of the Inria team of Nicholas Ayache and Hervé Delingette in Sophia Antipolis. It was built using high-resolution MRI scans of anatomical parts, on which a medical expert had precisely delineated the structures of the cochlea. Applied to low-resolution images taken in clinical practice, the model restitutes the three-dimensional structure of the cochlea of each patient with its internal compartments. For the first time, the individual anatomical variations of the cochlea could be identified on a series of 987 scans provided by Charles Raffaelli, radiologist at the Pasteur Hospital of the Nice University Hospital Center. For Oticon Medical, this information is particularly useful to further improve the design of cochlear implant electrodes, and reduce the trauma they can cause.

First use in cochlear implant surgery

The software program detects potential shape anomalies and extracts the specific parameters of each patient. First used on archive images, the model has now reached the stage of clinical application. It was used in two cochlear implant operations carried out at the end of May by Nicolas Guevara, ENT surgeon at the Face and Neck University Institute in Nice. He planned the surgery using the 3D images and the individual parameters of each patient. This information could be used among other things to predict the optimal angle to insert the electrodes, and limit the risk of trauma on a short cochlea. Further images are taken after the operation to show the position of the electrodes in the cochlear structures. They provide information on the quality of the implant, and are useful for adjusting each electrode individually when activating the implant. This research collaboration is the opportunity to clarify the model's potential as a tool for planning surgery and customizing implant settings, for the benefit of patients with severe deafness.

Photo Credit: A. Macarri - Université Côte d'Azur