Auditory brainstem implantation in primates: lessons for human surgery andapplication

We report on the surgical technique for surface electro-auditory prosthesis (EAP) implantation, pathological changes occurring at the cochlear nucleus complex (CNC), and its relation with electrical stimulation. Fourteen Maca ca fascicularis were operated upon for a translabyrinthine bilateral audito ry neurectomy, and simultaneous unilateral EAP implantation. Six animals we re not stimulated, and the remaining eight were connected to an external ac tive device. Stimulation was planned for 1000 hours. Biotolerance to the ma terials was adequate without significant reactions in the CNC surface, but an ependymal reaction. Lesions attributed to surgical trauma were also foun d. Two animals being stimulated could not complete the planned course due t o cable break or EAP extrusion. One stimulated animal developed an asymptom atic brainstem abscess. A good knowledge of CNC topography is required to a void surgical trauma. Externally connected devices may facilitate extrusion of the EAP or ascending infections.