The goal of this clinical research study is to establish the safety of simultaneous infusions
of methotrexate and etoposide into the fourth ventricle of the brain or resection cavity in
patients with recurrent malignant posterior fossa brain tumors. These tumors include
medulloblastoma, ependymoma, atypical teratoid/rhabdoid tumor or other malignant brain tumor
with recurrence or progression involving anywhere in the brain and/or spine. Patients'
disease must have originated in the posterior fossa of the brain.