Cavernous angiomas of the brain stem. Intra-axial anatomical pitfalls and surgical strategies.

We review the surgical anatomy of the brain stem in relation to the surgical approaches adopted for treatment of cavernomas and identify possible "safe entry zones" on the anterior face of the brainstem. Twelve symptomatic patients with cavernoma or telangectasia of the brain stem were surgically treated. The brain stem was divided into the following anatomical areas: ventral medulla, dorsal medulla, dorsal pons, ventral pons, ventral mesencephalon, and dorsal mesencephalon, so that the surgical approach could be "individualized" according to the position of the cavernoma, the nerve fasciculi and nuclei. On the anterior surface of the brain stem a medullar paramedian oblique access to the anterolateral sulcus and a paramedian sagittal pons access seem to avoid the main nerve fasciculi and nuclei.