RATIONALE: Drugs used in chemotherapy, such as melphalan, work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing. Giving drugs directly into the arteries around the tumor may kill more tumor cells. Mannitol may open the blood vessels around the brain [Blood-Brain Barrier Disruption (BBBD)]and allow melphalan to be carried directly to the brain tumor. Giving melphalan together with BBBD may be an effective treatment for central nervous system cancer.