Surgical Strategy for Brainstem Cavernomas: Nexus of Anatomy, Pathology, and Ergonomics

Brainstem cavernomas were once considered inoperable and were associated with significant surgical morbidity. However, the development of different microsurgical approaches and advancement in neuroimaging and neuronavigation have allowed for safer resection. Due to the very dense composition of cranial nerve nuclei and tracts in a small cross-sectional area, operating within the brainstem can be associated with significant morbidity, particularly for lesions that do not reach a pial or ependymal surface. Knowledge of “safe entry zones” of the brainstem is critical to reduce morbidity in these scenarios. While no area of the brainstem is truly “safe,” these regions merely represent entry points between eloquent neural structures through which a lesion can be accessed with the least possible damage. This chapter discusses the 18 main entry zones that have been described in the literature. It also reviews the relevant anatomy, the main entry zones of the brainstem, and the surgical approaches utilized to access them with corresponding illustrative cases. Surgical nuances and common pitfalls are reviewed at the end of the chapter.