Abstract
Surgical lesions in the 4th ventricle and brainstem include medulloblastoma, ependymoma, astrocytoma, choroid plexus papilloma, cavernous malformation of the brainstem, hemangioblastoma, exophytic glioma, and so on. To expose the 4th ventricle, the tela choroidea and taenia choroidea of the 4th ventricle are divided to retract the cerebellar tonsilla (trans-cerebello-medullary fissure approach). Entry into the brainstem must be made at the most accessible part. On the 4th ventricle floor, important structures such as the median sulcus, obex, striae medullares, lateral recess, and facial colliculus are easily identified. The abducens nucleus and facial nerve are located beneath the facial colliculus. To save these structures, supra-facial and infra-facial triangle approaches are useful. On the other hand, important nuclei are located in the caudal half of the 4th ventricle floor, such as the hypoglossal nucleus, vagal nucleus, solitary nucleus, and so on. Care must also be taken to prevent cardiac arrest or dysphagia. To approach the ventro-lateral aspect of the brainstem, the anterior transpetrosal approach is the approach of choice. These approaches are presented using cases with brainstem cavernous malformations.
