In this chapter, the cavernomas of the cerebellopontine angle, found on the surface of cranial nerves, and the brainstem cavernomas that can be surgically treated through the retrosigmoid approach are reviewed. Cerebellopontine angle cavernomas are rare lesions, but brainstem cavernomas are more frequently diagnosed. Cerebellopontine angle and brainstem cavernomas must be treated by microneurosurgical excision after diagnosis due to their high rate of bleeding and rebleeding. Cavernomas are resected through a retrosigmoid approach. Cavernomas of the anterolateral surface of the brainstem are removed using safe entry zones and a delicate microneurosurgical technique. In the chapter are described these anatomical safe entry zones to the midbrain, pons, and medulla oblongata.