Batch fabrication of 3D neural interface and surgical pathway planning for auditory cortical prosthesis

The first and the most successful auditory prostheses are cochlear implants; they are used by over 188,000 people worldwide. However, cochlear implants are only indicated for subjects with existing auditory nerve functionality. Subsets of deaf subjects do not have functional auditory nerve, for example, those affected by Neurofibromatosis type II NF-II). NF-II is a genetic auditory nerve tumor disease that occurs in about 1 in 40,000 births. An Auditory Cortical Prosthesis (ACP) is an alternative approach for hearing restoration in these deaf individuals. ACP bypasses the auditory nerve and stimulates the primary auditory cortex directly. ACP consists of a neural interface that electrically stimulates the auditory cortex. The size, shape and location of the electrode are key parameters in performance of an ACP. In the present study we use high resolution functional Magnetic Resonant Imaging (fMRI) to explore the primary auditory cortex (of normal hearing patients). The results will be used in establishing methods that will optimally design a subject-specific ACP neural interface. NF-II subject posses relatively normal hearing before undergoing tumor removal surgery therefore the method presented in this study also can be applied to NF-II subjects. Longevity of the electrode-tissue interface for cortical prostheses has long been a limiting factor for clinical implementation. We have manufactured a novel 3-Dimensional flexible neurotrophic electrode to establish the required long-lasting connection between neurons and the electrode. The 3-Dimensional structure of the device allows neurite in-growth, establishing a high-fidelity connection between the device and neurons. The electrodes are polyimide based which makes them flexible. In comparison to traditional stiff electrodes, flexible electrodes better match the mechanical properties of the brain and are resistive to brain-dura microstress. Our electrodes consist of a polyimide bi-layer thickness, ∼5 um per layer) with a platinum layer of 300 nm in between. The 3D tunnel structure is designed to be filled and covered with neurotrophic factors to attract the neurons.