Inter- and intra-patient variability of facial nerve response areas in the floor of the 4th ventricle

Introduction: The brainstem has a complex and dense anatomy and therefore the surgery of brainstem lesions requires precise localization of the surrounding healthy tissue. It is well known that the fibers of the facial nerve (CN VII) reach the surface of the rhomboid fossa at the level of the facial colliculus. However, the shape and size of the area where the facial nerve can be stimulated has not yet been systematically assessed. Methods: Over a period of 18 months, 20 patients were operated on for various brainstem and/or cerebellar lesions via the telovelar approach that gave wide access to the rhomboid foss…