The cochlear implant has achieved remarkable success in restoring hearing to deaf individuals through electrical stimulation of remaining nerve fibers near the cochlea. Unfortunately, cochlear implants are ineffective for those without a functional auditory nerve or implantable cochlea required for implementation. For these individuals, the only option is central auditory stimulation and the only FDA-approved device is the auditory brainstem implant (ABI), which is designed for stimulation of the cochlear nucleus. The ABI is mostly implanted in neurofibromatosis type 2 (NF2) patients who already have to undergo open head surgery to remove a tumor at the brainstem level and become deaf due to tumor-related damage of the auditory nerves. Although the ABI provides hearing improvements to these patients on a daily basis, it generally does not provide sufficient speech perception. One hypothesis is that the tumor removal process may damage brainstem structures crucial for speech understanding that can no longer be effectively activated with the ABI. To bypass this damaged region, a new auditory midbrain implant (AMI) was developed to stimulate in a higher structure, the inferior colliculus (IC). The IC has a well-defined tonotopic organization and is more surgically accessible than the cochlear nucleus, making it a favorable target for a new auditory implant. In a previous clinical trial, five NF2 patients were implanted with a single-shan array AMI device, which has shown to be safe and reliable for over six years. However, none of the patients have achieved sufficient speech understanding. Proceeding animal and human studies have identified the need for a new two-shank array that can more effectively activate across the three-dimensional IC structure. An improved surgical approach has also been developed for more consistently positioning the two-shank array into appropriate regions of the IC. The proposed project is a Phase I clinical study with the primary objective to demonstrate the safety and consistency of implantation and stimulation of this new two-shank AMI device in five NF2 patients at the leading auditory implant center in Germany. The secondary objective is to then show that this new implant can significantly improve hearing performance compared to the single-shank AMI and current ABI devices. To justify implantation of this new AMI device, only patients who have already been implanted with an ABI and achieve no or minimal benefit will be selected for this study. In other words, the AMI is their only hearing option. Each patient will be closely monitored across 8 to 10 testing sessions over a two year period to confirm the safety and reliability of the device over time. Various evaluations, speech tests, and psychophysical tests will also be performed to assess hearing performance with the AMI and to improve the stimulation strategies. Achieving the objectives of this study will justify proceeding Phase II/III trials and hopefully lead to commercialization of an improved central auditory prosthesis to benefit thousands of deaf patients worldwide.
The proposed Phase I clinical study will investigate the safety and functionality of a new two-shank central auditory prosthesis that may improve hearing performance over current devices and could benefit over 200,000 deaf individuals. This new central prosthesis is more technologically advanced than current deep brain stimulation devices, which are already implanted in over 100,000 patients with various neurological disorders. Demonstrating the safety and reliability of this new device could expand its use for treating millions of patients suffering from other conditions that require activation of deep brain structures.