 This pilot trial studies the brain concentration of eribulin mesylate in treating patients with primary or metastatic brain tumors. Drugs used in chemotherapy, such as eribulin mesylate, work in different ways to stop the growth of tumor cells, either by killing the cells, by stopping them from dividing, or by stopping them from spreading. Collecting small samples of brain fluids may help determine how well eribulin mesylate concentrates into the brain tumor. 