Surgical accessibility of the cochlear nuclear complex in man: surgical landmarks

Patients deafened by bilateral acoustic tumors or by transections of both cochlear nerves are excluded as candidates for cochlear implantation. These patients require more proximal stimulation of the auditory pathway. One potential area for such stimulation is the cochlear nuclear complex (CNC) in the lateral recess of the fourth ventricle. If animal studies establish the safety and efficacy of such stimulation, electrical stimulation of the human cochlear nuclear complex may become an accepted treatment modality for this select group of patients. Such implantation requires that the surgeon accurately locate the cochlear nuclear complex without destruction of vital surrounding neural and vascular structures. With ten fresh human brains, oriented for a translabyrinthine approach, we determined key anatomical landmarks to the exposed surface of the CNC on both sides of each brain. Using a combination of anatomical landmarks--including the flocculus, eighth nerve root, choroid plexus, and taenia--we located the cochlear nuclear complex (without disruption of surrounding neural or vascular structures) and marked it with colloidal carbon. Access to the CNC was obtained in all 20 specimens, and histologic sections confirmed the carbon marker in the CNC in 19 of 20 specimens.