Anatomy and Challenges for Surgical Removal of Brainstem Tumors: The Mesencephalic Region

Brainstem tumors represent a group of heterogeneous lesions with different biological behaviors. The possibilities for surgical resection and cure vary according to histology, location, extension, infiltration, and macroscopic appearance. Cavernous angiomas are the paradigm for surgical indication as removal may cure the patient, whereas conservative treatment sometimes leads to disability and even death due to fatal bleeding. Mainstay of the management is based on surgical indication, decision about surgical approach/entrance in the brainstem (with special emphasis on the concept of safe entry zone), and finally the resection and preservation of neural structures. This chapter deals with the principles of microsurgical resection of tumors at the brainstem, surgical indication, and anatomical basis of the surgical approaches and brainstem access.