Surgical Removal of Ventral Lower Pontine Cavernous Angiomas: Surgical Approach and Safe Entry Zone to the Brain Stem

We report 2 patients whose lower ventral pontine cavernous angiomas were removed via the ventral lower pons lateral to the abducens nerve where the angiomas are closest to the surface of the brain stem. A suboccipital transcondylar approach (STC) provided a sufficient operative field to remove the angiomas from the lower pons lateral to the abducens nerve and an adequate operative trajectory along the longitudinal axis of the angiomas. Successful removal was accomplished without serious complications in both cases. As the cranial nerve nuclei and the reticular formation were displaced dorsally, the corticospinal tract was located medial to the abducens nerve, and the facial nerve fibers were running laterally in our 2 cases. The lower pons lateral to the abducens nerve was a safe entry zone into the brain stem. Bone removal around the condylar emissary vein, the posterior part of occipital condyle, the hypoglossal canal and the jugular tuberculum in STC provided an extensive operative field in ventral aspects of the medulla and lower pons. The patient's position during surgery was important to facilitate bony removal and provide an adequate operative trajectory. Volume reduction with electrocoagulation and piecemeal resection proved to be essential techniques for safe and complete removal of the brain stem cavernous angiomas.